Drone monitoring of endangered scalloped hammerhead shark Sphyrna lewini movements and habitat use on a dynamic urbanised coastline in Australia

Drone monitoring of endangered scalloped hammerhead shark Sphyrna lewini movements and habitat use on a dynamic urbanised coastline in Australia | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Drone monitoring of endangered scalloped hammerhead shark Sphyrna lewini movements and habitat use on a dynamic urbanised coastline in Australia Maddison Colby Cross, Bonnie J. Holmes, Matthew N. McMillan, Johan A. Gustafson, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8769949/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Many elasmobranch species face increasing pressures from overfishing, habitat degradation, and coastal development, yet their movement ecology remains poorly understood. Unmanned Aerial Vehicles or drones offer a non-invasive method to study the distribution and habitat use of species frequenting inshore areas. Scalloped hammerhead sharks ( Sphyrna lewini ), listed as Critically Endangered on the International Union for the Conservation of Nature (IUCN) Red List, have experienced global population declines prompting the need for research that identifies key habitats, including nursery and aggregation sites. This study analysed archived footage from the Queensland SharkSmart drone program at nine beaches in southeast Queensland between September 2020 and December 2024. The frequency of scalloped hammerhead sightings was quantified, along with the influence of environmental, biotic, and operational variables on sightability. Ninety sightings were recorded, primarily between April and June. Sightings were significantly influenced by turbidity, presence of other fauna, time of day, month, and location. Aggregations of up to 80 juvenile sharks (estimated mean total length 109 cm ± 25 cm) were observed at Burleigh Beach, with additional sightings at Noosa Main Beach. These findings provide new insights into the species’ spatial ecology in southeast Queensland, Australia and demonstrate the value of drone monitoring for conservation and spatial management. aerial surveys spatial ecology critical habitat juvenile sharks elasmobranchs Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Understanding the movements and habitat use of endangered marine species is fundamental to their conservation, as it informs spatial management and the protection of critical life stages such as breeding, nursery and aggregation sites. However, monitoring marine megafauna in dynamic coastal environments remains a significant challenge due to factors such as turbidity, complex bathymetry, and the logistical and cost constraints of traditional survey methods limiting data availability (Butcher et al. 2019 ; Cross et al. 2024 ). Elasmobranchs (sharks and rays) can be particularly vulnerable to anthropogenic pressures in these coastal areas, including overfishing, habitat degradation, and rapid urban development (Dulvy et al. 2014 ; Pacoureau et al. 2021 ). Urban-driven alterations to these habitats can disrupt key behaviours in elasmobranchs, including foraging, migration, and parturition (Heupel et al. 2007 ; Todd et al. 2019 ). Given their proximity to these areas, many coastal species are facing significant global population declines, and key aspects of their movement ecology and habitat use remain poorly understood, complicating efforts to develop targeted conservation and management strategies. Among the more imperilled species, scalloped hammerhead sharks ( Sphyrna lewini ) have undergone steep population declines worldwide, with estimates exceeding 80% (Pacoureau et al. 2021 ; Lopez et al. 2023). As a result, the International Union for Conservation of Nature (IUCN) classified the species as Critically Endangered under criterion A2bd (Rigby et al. 2019 ), which reflects an estimated median global population reduction of 76.9–97.3% over three generation lengths (72.3 years). They are also listed in Appendix ІІ of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). While global populations continue to decline, Australia’s relatively healthy stocks position it as a ‘lifeboat’ nation, offering both a refuge for the species and a valuable opportunity for conservation research. Within Australia, they are listed as ‘Conservation Dependent’ under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC ACT 2018) and they have been a no-take species in Queensland waters since 2024 (Queensland Government 2025 ). To support effective conservation strategies, there is an urgent need to identify critical habitats, including breeding, parturition, nursery, and aggregation sites, particularly in regions like Australia, where the species remains accessible for study, and to apply these insights to areas where populations have been severely depleted or extirpated. Scalloped hammerheads have a circumglobal distribution, inhabiting tropical and warm temperate waters (Compagno 1984 ). This species is highly mobile, capable of migrating over 1,000 km (Bessudo et al. 2011 ; Spaet et al. 2017 ), and occurs across a mosaic of ecosystems, including, estuaries, bays, continental shelfs, and offshore pelagic waters (Wells et al. 2018 ). Despite their migratory capacity, studies have found that most scalloped hammerheads have relatively small home ranges and display aggregative behaviours around bathymetric features, such as seamounts, likely influenced by environmental factors (Klimley et al. 1988 ; Holland et al. 1993 ; Hearn et al. 2010 ; Bessudo et al. 2011 ; Lopez et al. 2023). These aggregations are subject to sexual segregation, with adult males and females typically occupying different spatial regions within their overall distribution (Klimley 1987 ; Stevens and Lyle 1989 ; Harry et al. 2011 ). Mature females, although rarely observed, are believed to primarily inhabit offshore, pelagic waters, whereas males tend to remain closer to coastal areas (Harry et al. 2011 ; Hoyos-Padilla et al. 2014 ; Wells et al. 2018 ). During warmer summer months, pregnant females are thought to migrate inshore to give birth, typically producing litters of 10 to 14 pups (Stevens and Lyle 1989 ; Harry et al. 2011 ). Neonates and juveniles are predominantly found in shallow, turbid coastal nursery areas, where they remain for several months (Simpfendorfer and Milward 1993 ; Yates et al. 2015 ; Brown et al. 2016 ; Zanella et al. 2019 ). Scalloped hammerhead pups are born at sizes ranging from approximately 31 to 57 cm in total length, with sexual maturity attained at lengths of around 140–198 cm for males and 200–250 cm for females, and maximum sizes reaching up to 430 cm (Ebert et al. 2021 ). However, knowledge gaps remain in Australia regarding their seasonal habitat preferences, the duration of their stay in nursery areas, and their subsequent movements after leaving these regions (Simpfendorfer and Milward 1993 ; Duncan and Holland 2006 ; Hutchinson et al. 2023 ). Unmanned Aerial Vehicles (UAVs; hereafter referred to as ‘drones’) offer a unique vantage point for observing marine megafauna and have been increasingly used in recent years to identify important habitats for elasmobranchs (Raoult et al. 2018 ; Ayres et al. 2021 ). Drones are especially advantageous for shark research, providing non-invasive monitoring with minimal disturbance to the species, a critical consideration for understanding natural behaviour and movements (Butcher at al. 2021; McIvor et al. 2022 ; Cross et al. 2025 ). Studies have demonstrated the utility of drones in detecting sharks off coastal beaches (Kelaher et al. 2019 ; Mitchell et al. 2022b ; Cross et al. 2024 ), highlighting their potential for detecting the presence of scalloped hammerhead sharks. This is emphasised in a recent study by Lopez et al. (2022), which used drones to monitor a seasonal scalloped hammerhead aggregation in Western Australia. The study documented aggregation size and structure, behavioural interactions, and environmental drivers influencing the timing and presence. This aggregation extended the southern range of the species in Australia, and the findings were used to make recommendations for improved coastal zone management and marine park planning, supporting the need for protection of this aggregation site (Lopez et al. 2023). Since September 2020, the Queensland SharkSmart drone program has monitored sharks for public safety purposes at up to nine beaches in southeast Queensland, Australia (Mitchell et al. 2022a ; Mitchell et al. 2025 ). The program has recorded a total of 4,959 sharks from September 2020 to April 2024, across 16,601 flights (Mitchell et al. 2025 ). A range of environmental and biotic factors were found to influence shark sightability, including the sighting of other fauna, season, wind speed and direction, turbidity, tidal state, glare, and atmospheric pressure (Mitchell et al. 2025 ). The archived footage represents an important resource for documenting marine megafauna biodiversity, abundance, and behaviour. This study used the archived footage from the Queensland SharkSmart drone program to assess sightings of scalloped hammerhead sharks off coastal beaches of southeast Queensland between September 2020 to December 2024. Specifically, the objectives of this study were to identify how frequently scalloped hammerhead sharks were sighted off these coastal beaches and quantify the influence of environmental, biotic, and operational factors on their sightability. Additionally, this study aimed to determine the presence of important habitats for the species, such as those supporting aggregations and juveniles. Materials and methods Study site and drone flights From 2020 to 2024, the Queensland SharkSmart drone program operated at nine beach locations in southeast Queensland (Fig. 1), as described in Mitchell et al. (2025). Pilots from Surf Life Saving Queensland fly drone surveys on weekends, public holidays, and school holidays when weather permits, completing 8-10 flights per day between 07:00 and 12:00. Flight transects were 400 m long behind the surf break (~200 m offshore), with multiple passes of the transect occurring (Fig. 2; Cross et al. 2024). Drone footage was recorded in 4k high definition and archived for later analysis. Shark sightings were recorded, including an estimate of animal total length, direction of movement, and proximity to the beach. A range of environmental variables were also recorded for each flight (Table 1; Mitchell et al. 2025). Species could only be determined for distinctive species, including white shark ( Carcharodon carcharias ), tiger shark ( Galeocerdo cuvier ), bull shark ( Carcharhinus leucas ), and leopard shark ( Stegostoma tigrinum). In other cases, sharks were recorded into categories including whaler sharks ( Carcharhinus spp.) and hammerhead sharks at initial classification. This species complex could therefore include any scalloped ( Sphyrna lewini ), great ( S. mokarran ) or smooth ( S. zygaena ) hammerheads, based on their distribution (Compagno 1984). Further species-specific identification was confirmed using high-resolution stills extracted from the footage, focusing on clear images of individuals swimming close to the surface that displayed distinctive morphological features, including a scalloped cephalofoil (head shape) and central indentation (Fig. 3). All confirmed sightings were scalloped hammerheads ( S. lewini ). Therefore, other species were omitted from the dataset based on these clear morphological distinctions. Table 1. Environmental, biotic, and operational factors included in the Generalised Additive Models (GAMs) to assess the likelihood of sighting scalloped hammerhead sharks. Factor Type Factor Unit of measurement/notes Environmental Month January-December Environmental Rainfall mm/day Environmental Air temperature °C Environmental Turbidity 0-100 % Environmental Sea state Beaufort Scale (low =1, high = 12) Environmental Wind speed km h−1 Environmental Cloud cover Oktas Environmental Glare 1 (low)-5(high) scale Environmental Atmospheric pressure hPa Biotic Presence of other fauna Bait balls, fish, rays, marine mammals Operational Location Beach Operational Flight number (time of day) Flight number (1-8) Data collection for scalloped hammerhead sharks For each sighting, species, number of animals present, presence of other fauna, and the sharks’ movement track were recorded. Movement tracks were generated using QGIS (v3.32.2-Lima; 2023; see Cross et al. 2025 for track methods). Movement tracks recorded represent the flight path of the drone’s position rather than the precise movements of the sharks. To ensure accuracy, only instances where the drone was closely aligned above the shark were included in analysis. Previous research by Raoult et al. (2018) demonstrated that drones flown directly overhead can provide highly precise trajectory data for sharks. However, in cases involving large schools of sharks, the tracks reflect general activity and fine-scale habitat use patterns rather than the directional movements of individual animals, due to difficulty distinguishing individuals within aggregations. To account for differences in survey effort among locations, the total number of flights at each site was converted into effort hours (two flights per hour), and sighting rates were calculated as the number of hammerhead shark events or individuals per flight hour. Total length of each scalloped hammerhead shark was estimated by comparing the shark’s size to nearby reference objects visible in the footage, such as swimmers, surfboards, paddleboards, and other marine animals (Fig. 4). For paddleboards, an average length of 3.15 m (range: 2.8 – 3.5 m) was used based on standard dimensions. Shark length was estimated by assessing the relative size of the shark to the reference object within the same frame (Graham and Roberts 2007). In instances where no reliable scale objects were present, footage from the same area and day when reference objects were available, was used to approximate scale. If no suitable reference could be established, the shark was excluded from length analysis. Statistical analysis Kernel Density Estimation (KDE) heatmaps of individual scalloped hammerhead shark tracks were generated using QGIS. Only Burleigh Beach and Noosa Main Beach were selected due to high shark sighting frequencies and clear recurring patterns of use. KDE analysis was conducted by interpolating shark track points into a heatmap using a 10 m cell size, following methods outlined in Cross et al. (2025). A Generalised Additive Model (GAM) was used to quantify the influence of environmental, biotic, and operational factors on the likelihood of observing scalloped hammerhead sharks (Table 1). Presence or absence of scalloped hammerhead sharks was used as the response with a binomial distribution. To account for the vastly different number of flights conducted at each location and differences in scalloped hammerhead sightings, location was included as a random effect in the model. Prior to model fitting, Pearson correlation coefficients were calculated for continuous predictor variables to identify and avoid multicollinearity; any pairs with a correlation coefficient greater than 0.5 were not used in the same model. The distribution of predictor variables were visually inspected, and where distributions were skewed, square root or log(x+1) transformations were applied. Model selection was performed using a backward stepwise approach, sequentially removing individual predictor variables and monitoring changes in the Akaike Information Criterion (AIC; Akaike 1974). The final model was selected based on the lowest AIC value and inclusion of only statistically significant predictor variables. All statistical analyses were conducted in RStudio (R v4.4.1; RStudio v1.4.1711; R Core Team 2023). The mgcv package (v1.9.3; Wood 2017) was used to build GAMs, and the tidyverse package (v1.3.2; Wickham et al. 2019) was used for data organisation and visualisation. Results Scalloped hammerhead sightings Across the nine southeast Queensland beaches monitored by the SharkSmart drone program, a total of 90 scalloped hammerhead shark sighting events were recorded from the 20,911 drone flights between September 2020 to December 2024, comprising 2,696 individual sharks in total. The majority of sightings occurred at Burleigh Beach (Gold Coast) and Noosa Main Beach (Sunshine Coast), where sighting rates were highest (0.026 and 0.032 events/hr, and 1.105 and 1.015 individuals/hr, respectively; Table 2). Many sharks at these locations were likely resighted across multiple flights, and as such, this figure does not represent the total number of unique individuals. Sightings at Burleigh and Noosa almost exclusively involved groups of multiple animals, whereas other beaches generally involved solitary individuals or pairs (Table 2). Group size ranged from one to 100 individuals, and estimated total lengths varied from <0.80 m to 3 m (mean ± SD: 109 ± 25 cm; Fig. S1). Juveniles dominated sightings at Burleigh and Noosa, while larger individuals were more frequently observed off North Stradbroke Island. Table 2. Summary of scalloped hammerhead shark sightings across nine southeast Queensland beach locations covered by the SharkSmart drone program, including standardised sighting events. Beach location No. of flights No. of hammerhead sighting events No. of individuals a Sighting rate (events/hr) Individuals/hr Total length (TL) range (cm) Group size range Alexandra Headlands 3,277 1 1 0.001 0.001 <100 1 Bribie Island 1,183 2 2 0.003 0.003 100 - 200 1 Burleigh 3,091 40 1,708 0.026 1.105 0.80 - 150 1 - 80 Coolum 3,008 0 0 0 0 - - Kurrawa 1,730 0 0 0 0 - - Noosa 1,907 31 968 0.032 1.015 <100 1 - 100 North Stradbroke Island 1,885 14 14 0.015 0.015 150 - 300 1 - 2 Rainbow Beach 1,787 0 0 0 0 - - Southport 3,043 2 3 0.001 0.002 100 - 250 1 - 2 Total 20,911 90 2,696 0.009 0.258 0.80 - 300 1 - 100 a Includes repeated sightings of the same individuals Movement patterns and space use Scalloped hammerhead sharks displayed variable movement patterns and space use off the surveyed coastal beaches. At North Stradbroke Island (Fig. 5A), 13 of the 14 sharks moved northeast parallel to the shoreline, following linear trajectories with minimal deviation in direction. Most individuals were tracked for approximately 100 m, although one shark was tracked for approximately 250 m. The remaining individual also exhibited a linear trajectory but travelled eastward. In contrast, observations at Burleigh Beach revealed more clustered movement patterns, particularly during aggregations between March and early June (Fig. 5B). Tracks from 1 April 2023 (yellow) and 3 April 2024 (red) showed frequent overlap and repeated use of the same coastal areas, with each track representing movements of multiple scalloped hammerheads observed on a single drone flight during the aggregation period. Kernel density heatmaps revealed consistent spatial hotspots at Burleigh across both years (Figs. 6A and 6B), with sightings concentrated near the southern end of Burleigh Beach near Burleigh Headland. A similar pattern of localised space use was evident at Noosa Beach from 6 April to 30 June 2023 (Fig. 6C). However, scalloped hammerheads were not observed at Noosa during the same period in 2024, unlike the persistent aggregations observed at Burleigh Beach. During the 2023 aggregation season, shark presence was documented in three main areas. The central hotspot, adjacent to Noosa Main Beach, showed the highest sighting density, with two additional zones of moderate activity extending to the east and west. Factors influencing hammerhead shark presence The best ranked model with the lowest AIC value identified turbidity, presence of other fauna, sea state, flight number (proxy for time of day), month and location as significant predictors of hammerhead shark sightability (Table S1). These variables collectively explained 33% of the deviance in the response variable (Tjur’s R² = 0.094; Table S2). Sightings were negatively associated with increasing turbidity (Fig. 7A) and higher sea states (Fig. 7B), with the highest probability of sightings observed in clear (0.015 ± 0.007) and calm (0.011 ± 0.005) conditions. The presence of other fauna significantly increased the likelihood of hammerhead sightings (0.015 ± 0.006; Fig. 7C). Within the morning survey period, the probability of sightings declined over time, with earlier flights sighting significantly more sharks (0.005 ± 0.002; Fig. 7D). Temporal analysis revealed a seasonal pattern, with peak sighting probabilities occurring between April (0.011 ± 0.005) and June (0.005 ± 0.002), and lower probabilities recorded during the summer months (0.001 ± 0.001; Fig. 7E). Spatial variation in sightings was evident, with the highest probabilities of hammerhead presence observed at Burleigh (0.013 ± 0.005) and Noosa (0.012 ± 0.005) beaches (Fig. 7F). Discussion This study highlights drones as a highly effective, non-invasive tool for detecting fine-scale habitat use of scalloped hammerhead sharks ( Sphyrna lewini ). Here, we demonstrate the successful detection of spatio-temporal hammerhead aggregations at popular urbanised beach sites that serve as important habitat for these juveniles at this critical life history stage. Further, these sharks were previously undetected at these same locations through traditional monitoring programs, indicating the viability of deploying UAVs as an emerging tool for research on critically endangered elasmobranchs. The repeated detection of juvenile scalloped hammerheads, particularly in large aggregations at Burleigh and Noosa, suggests that these sites may provide critical habitat features that enhance survival and growth, such as abundant prey, structural refuge, and reduced predation risk (Brown et al. 2016 ). In contrast, the predominance of solitary individuals at Bribie Island, North Stradbroke Island, and Southport Main Beach highlights fine-scale spatial heterogeneity in habitat suitability, indicating that juveniles may actively partition space to balance resource acquisition with predator avoidance. These spatial patterns align with observations from the Eastern Tropical Pacific (including Colombia and the Galapagos Islands) and Central Pacific (Hawaii), where scalloped hammerheads exhibit strong site selectivity (Hearn et al. 2010 ; Bessudo et al. 2011 ) and occupy small core areas during daylight hours (Klimley et al. 1988 ; Holland et al. 1993 ). Collectively, these findings suggest that juvenile scalloped hammerheads are not randomly distributed but instead exhibit strategic habitat selection influenced by a combination of biotic and abiotic factors, including prey availability, refugia, and local environmental conditions. Although the observed individuals comprised a mix of young-of-the-year and older juveniles (1–2 years old; Harry et al. 2011 ; Lubitz et al. 2025 ) rather than neonates, the repeated occurrence of similar sized sharks across multiple months and years suggests seasonal and interannual use of these areas. While these coastal zones may not meet the criteria for nursery areas as defined by Heupel et al. ( 2007 ), they likely serve as important juvenile aggregation areas. Notably, the sampled beaches are located within 20–60 km of several estuarine and embayment systems, including Moreton Bay, Broadwater, and associated river mouths, which have been proposed as potential nursery grounds for scalloped hammerheads in this region (Gustafson 2020 ). The presence of older juveniles at coastal beach sites may therefore reflect an ontogenetic shift in habitat use, with individuals dispersing from sheltered nursery areas as their energetic requirements and prey preferences change with development. Aggregations occurred consistently between March and June, which overlaps with the known regional pupping season for scalloped hammerhead sharks (Stevens and Lyle 1989 ; Harry et al. 2011 ; Gustafson 2020 ), although the individuals observed during this period were likely born in previous years. This seasonal timing may still be ecologically significant, as warmer water temperatures during these months can increase prey availability and support elevated metabolic and growth rates in juveniles (Simpfendorfer and Milward 1993 ; Duncan and Holland 2006 ; Niella et al. 2020 ). These conditions may make adjacent coastal habitats particularly favourable for older juveniles during this time of year. Together, these findings support the hypothesis that coastal zones act as transitional developmental habitats and underscore the need for long-term monitoring, particularly through acoustic telemetry, to confirm connectivity with nearby nurseries and identify the environmental drivers shaping juvenile distribution. Movement patterns varied across locations, reflecting differences in how scalloped hammerhead sharks use coastal habitats across different life stages and regions. At North Stradbroke Island, scalloped hammerheads displayed linear, directed trajectories consistent with transitory movements by larger individuals (Harry et al. 2011 ; Wells et al. 2018 ). Given its proximity to the continental shelf (~ 23 km; Cross et al. 2024 ), this location may serve as a navigational aid during seasonal migrations (Klimley 1993 ; Holmes et al. 2014 ), particularly for mature scalloped hammerhead females moving towards the coast in summer and autumn. While these inshore movements coincide with periods of reproductive activity reported in eastern Australia and the broader Indo-Pacific (Stevens and Lyle 1989 ; Harry et al. 2011 ), the absence of long-term tracking data limits their interpretation as definitive reproductive migrations. Additionally, North Stradbroke Island lies within the influence of the East Australian Current (EAC), which brings warmer tropical waters during summer months (Suthers et al. 2011 ). This temperature variation may further influence seasonal movement patterns, with larger sharks potentially following thermal gradients for energetic efficiency or reproductive cues (Niella et al. 2020 ). The use of adjacent shallow areas may also provide thermal benefits or protection during these transits, although further research is needed to confirm the drivers of these movements (Holland et al. 1993 ; Klimley 1993 ). In contrast, juveniles at Burleigh Beach and Noosa Main Beach exhibited highly localised movements in shallow nearshore areas. At Burleigh, a rocky headland habitat appears to be a focal congregation point, suggesting that site fidelity may be driven by structural complexity, which supports higher prey abundance and diversity by providing both shelter and foraging opportunities for lower trophic levels (Ketchum et al. 2014 ; Yates et al. 2015 ; Brown et al. 2016 ). While aggregations of juvenile scalloped hammerheads have been rarely documented in Australian waters (Klimley 1983 ; Lopez et al. 2023; Lubitz et al. 2025 ), the repeated overlap of movements tracks at Burleigh across multiple years underscores its importance as an aggregation site. Such behaviour may reflect schooling for predator avoidance or improved foraging efficiency. Notably, core use areas ranged from 0.2 km 2 to 0.4 km 2 , closely matching the 0.2 km 2 core aggregation area reported in scalloped hammerhead sharks in Western Australia (Lopez et al. 2023), highlighting the critical role of small, localised habitats in supporting juveniles. These aggregations resemble those documented in the eastern Pacific, where juveniles display site-specific behaviours including resting and repeated co-occurrence, which may suggest social interactions (Klimley 1983 ; Klimley 1985 ; Ketchum et al. 2014 ; Papastamatiou et al. 2022 ). Scalloped hammerhead sightability was significantly influenced by environmental and operational variables. Visibility factors such as turbidity and sea state reduced sighting probability, consistent with previous drone-based elasmobranch studies (Raoult et al. 2018 ; Cross et al. 2024 ; Mitchell et al. 2025 ). These conditions not only limit aerial visibility but may influence shark behaviour, possibly reducing surface time or nearshore presence during rough conditions. Nonetheless, sharks may still be present under such conditions but remain undetected. In contrast, sightings increased when bait balls and teleosts were present, suggesting shared habitat use or foraging in productive zones, although reduced detectability under conditions of high turbidity or rough sea state may also have contributed. Given their diet of benthic teleosts and cephalopods (Rosende-Pereiro et al. 2020 ; Galloway et al. 2024 ; Páez-Rosas et al. 2024 ), this likely reflects prey-driven habitat selection. Estuarine outflows from nearby Tallebudgera Creek (Burleigh Beach) and the Noosa River (Noosa Main Beach) may enhance local productivity and prey abundance, contributing to consistently high hammerhead sightings (Meynecke et al. 2006 ; Connolly et al. 2009 ). Additionally, the presence of nearby reefs such as Burleigh Reef and Palm Beach Reef, both adjacent to Burleigh Beach, may provide structurally complex habitats that support diverse prey communities, further attracting scalloped hammerheads to this area (Henderson et al. 2022 ). Temporal patterns were also observed, with sightings more frequent during early morning flights, consistent with crepuscular activity in juveniles (Klimley et al. 1998; Bush 2003 ). However, surveys were restricted to morning hours, leaving much of the diel cycle unsampled and limiting broader temporal inference. The observed patterns are likely primarily driven by crepuscular foraging and movement behaviours, which are widely documented in scalloped hammerhead sharks (Klimley et al. 1998; Bush 2003 ; Ketchum et al. 2014 ; Lopez et al. 2023). Increasing human activity later in the morning may also contribute to reduced sighting rates, as sharks were observed avoiding snorkellers and paddle boarders, with aggregations occasionally disrupted. These behavioural responses align with studies reporting stress or site abandonment in elasmobranchs exposed to anthropogenic activity (Barker et al. 2011 ; Trave et al. 2017 ; Cattano et al. 2021 ). Seasonally, sightings peak between April and June, potentially linked to prey availability, as well as seasonal changes in the EAC, including both its strengthening and meanders, which can influence local oceanographic conditions (Suthers et al. 2011 ; Niella et al. 2020 ). Parturition, often occurring in warmer summer months in adjacent coastal embayments, may also contribute to seasonal peaks in abundance as these juveniles appear in these nearshore waters a few months later in the austral Autumn period (Simpfendorfer and Milward 1993 ; Duncan and Holland 2006 ; Hutchinson et al. 2023 ). Collectively, spatiotemporal trends suggest hammerhead presence is shaped by ecological productivity and habitat complexity, patterns observed not only in juvenile aggregations documented in southwest Western Australia (Lopez et al. 2022) but also around oceanic islands and seamounts in the Eastern Tropical Pacific (Hearn et al. 2010 ; Bessudo et al. 2011 ). Implications for conservation and monitoring Findings reported herein support the use of drones for targeted monitoring of endangered elasmobranchs. Importantly, the absence of escape or erratic responses indicates minimal disturbance to these sharks from drones, supporting their reliability and ongoing use for behavioural monitoring (Butcher et al. 2021 ; Mitchell et al. 2022b ). Drone-derived data offer a pathway for adaptive management, enabling dynamic, seasonally informed mitigation strategies that enhance both public safety and conservation outcomes. These insights can support marine spatial protections, including the designation of Essential Fish Habitat (EFH) under national legislation, and internationally, Important Shark and Ray Areas (ISRAs; https://sharkrayareas.org/about-isras/ ) to protect key habitats for sharks and rays. Moreover, drone observations can engage the public by presenting sharks in a natural context, potentially shifting perceptions and building support for conservation (Stokes et al. 2020 ; Cross et al. 2025 ). These data can also inform the development and promotion of codes of practice aimed at minimising human disturbance during shark interactions. While drones improve our ability to monitor these populations and inform management, existing human activities continue to impact these species. The high juvenile presence at Burleigh Beach and Noosa Main Beach highlights the need for seasonal spatial protections. However, both sites are part of the Queensland Government's Shark Control Program (QSCP) which aims to reduce the risk of shark bites using a combination of operational equipment (shark nets, baited drumlines, drones), research, trials and education. At Noosa, both shark nets and baited drumlines are operated, while Burleigh is equipped with shark nets only, which are located 300–500 m offshore. Between 2001 and 2024, the QSCP recorded 65 captures of scalloped hammerheads at Burleigh and Noosa combined, 63 in nets and two on drumlines, comprising both juveniles and adults (Queensland Department of Primary Industries 2025). Statewide, 675 scalloped hammerheads were captured over the same period, including 512 in nets and 163 on drumlines. Although not a target species, scalloped hammerheads are particularly susceptible to fishing mortality, and all but 10 individuals caught under the QSCP were deceased. Juvenile captures (< 120 cm) peak from September to February, coinciding with presumed nursery use, yet drone surveys documented aggregations from March to June, revealing a temporal mismatch. This discrepancy may reflect seasonal variation in depth and habitat use, with juveniles typically occupying surface waters and adults occurring closer to the seafloor (Lopez et al. 2023). The QSCP’s surface-set nets, which feature relatively large mesh sizes (~ 500 mm), likely influence the size classes caught. Most scalloped hammerheads recorded are < 200 cm in total length, indicating that juveniles and subadults are more susceptible to entanglement. Additionally, the offshore positioning of nets (~ 500 m from shore) may provide some spatial separation from inshore juvenile aggregations, further contributing to the mismatch between observed presence and recorded captures. Limitations and future directions Despite their utility, drones have inherent limitations. Drones cannot distinguish individual sharks (unless the animal has clearly distinctive markings or injuries), meaning repeated sightings may represent the same individuals. Their effectiveness is also constrained by favourable weather, water clarity, and depth, particularly because drone-based observations are typically limited to shallow (< 5 m), clear-water environments. This introduces a detection bias, as other potential aggregation sites in deeper or turbid waters may go undetected. Improvements such as polarising filters (Butcher et al. 2019 ), machine learning-assisted detection (Butcher et al. 2021 ), and geometric photogrammetry (Rex et al. 2024 ) could enhance the ability of drones to detect sharks in suboptimal conditions and demographic assessments. Future integration with acoustic telemetry, environmental DNA (eDNA) sampling, and photo-ID would support a more comprehensive understanding of site fidelity, population dynamics, and habitat connectivity, ultimately strengthening conservation outcomes. Declarations Competing interests The authors have no relevant financial or non-financial interests to disclose. Ethics approval This is an observational study. The Queensland Government has confirmed that no ethical approval is required. Funding Although this research did not receive external funding, the SharkSmart drone program is funded by the Queensland Government. Author contributions All authors contributed to the study conception and design. Material preparation, data collection, analysis, and data curation were performed by Maddison Cross. Methodology and software development were carried out by Maddison Cross, Tracey Scott-Holland, and Jonathan Mitchell. Validation was performed by all authors. Supervision was provided by Bonnie Holmes, Matthew McMillan, Johan Gustafson, and Jonathan Mitchell. The first draft of the manuscript was written by Maddison Cross, and all authors contributed to reviewing and editing subsequent versions. Project administration was led by Maddison Cross and Jonathan Mitchell. All authors read and approved the final manuscript. Acknowledgements The authors would like to thank the Surf Life Saving Queensland drone pilots for their role in collecting footage and data for the SharkSmart drone program. Gratitude is also extended to Rob Adsett, Greg Cahill, Damien Boyer and other staff members from Surf Life Saving Queensland for their support with logistics, project management, and administration. The authors thank Dr. Paul Butcher from the New South Wales Department of Primary Industries and Regional Development, along with Dr. Andrew Colefax and Dr. Justin Meager, for their scientific advice on the design and implementation of the Queensland SharkSmart drone program. The Queensland Government is acknowledged for funding all beach drone operations as part of the SharkSmart drone program. This research was supported by an Australian Government Research Training Program (RTP) Scholarship, the Queensland DPI Charter and Commercial Fishing Grant, and the Winifred Violet Scott Charitable Trust. Data availability Corres. author can provide the datasets used in this study upon reasonable request, although footage which contains images of people is considered confidential and cannot be made publicly available. References Akaike H (1974) A new look at the statistical model identification. IEEE Transactions on Automatic Control 19:716–723. 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Estuaries Coasts 38:2019–2030. https://doi.org/10.1007/s12237-015-9952-4 Zanella I, López-Garro A, Cure K (2019) Golfo Dulce: critical habitat and nursery area for juvenile scalloped hammerhead sharks Sphyrna lewini in the Eastern Tropical Pacific Seascape. Environ Biol Fish 102:1291–1300. https://doi.org/10.1007/s10641-019-00907-1 Supplementary Files ESM1.pdf Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 05 Feb, 2026 Reviewers invited by journal 05 Feb, 2026 Editor assigned by journal 03 Feb, 2026 First submitted to journal 02 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8769949","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":586449583,"identity":"56677dec-a650-443b-bbbe-d3db5a3785a9","order_by":0,"name":"Maddison Colby Cross","email":"data:image/png;base64,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","orcid":"https://orcid.org/0009-0002-4844-4164","institution":"University of the Sunshine Coast School of Science Technology and Engineering","correspondingAuthor":true,"prefix":"","firstName":"Maddison","middleName":"Colby","lastName":"Cross","suffix":""},{"id":586449584,"identity":"5ee90562-0664-4d49-bcc3-e245b1bf4c25","order_by":1,"name":"Bonnie J. 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The red circle highlights the 30 m public exclusion zone, from which drones were launched and retrieved.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/1921989d6d1c5df341b58a91.png"},{"id":102334376,"identity":"bc926477-fcb3-4c6a-b896-21b2de75b4a4","added_by":"auto","created_at":"2026-02-10 15:52:10","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":239570,"visible":true,"origin":"","legend":"\u003cp\u003eScalloped hammerhead sharks (Sphyrna lewini) observed during drone flights at Burleigh Beach, southeast Queensland. The image shows an individual swimming near the surface, with clear visibility of the species' distinctive scalloped cephalofoil (head shape) and central indentation, confirming species identification.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/721e06bbfef8fd5d2e428508.jpeg"},{"id":102334378,"identity":"e9cd4387-d265-426b-ae5d-b3731cf718b9","added_by":"auto","created_at":"2026-02-10 15:52:10","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":424292,"visible":true,"origin":"","legend":"\u003cp\u003eEstimation of total length using a visible reference object. For paddleboards, an average length of 3.15 m was used based on standard dimensions (range: 2.8 - 3.5 m). In this example, the sharks appear to be roughly one-third the length of the paddleboard, indicating an estimated total length of approximately 1.05 m.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/05e1bde6969525bb91c5b45a.png"},{"id":102334375,"identity":"0f7720d6-7903-46fa-a925-5e10fff6be45","added_by":"auto","created_at":"2026-02-10 15:52:10","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":454892,"visible":true,"origin":"","legend":"\u003cp\u003eRaw movement tracks of scalloped hammerhead sharks recorded from drone observations. A) Linear movement track of an individual shark at North Stradbroke Island in 2023. B) Aggregated movement patterns at Burleigh Beach in 2023 (yellow) and 2024 (red), illustrating increased localised space use.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/ade1ef82ddb5e4226dc97189.png"},{"id":102334379,"identity":"fd60025e-bac2-46af-8c71-124fa2ac5f7a","added_by":"auto","created_at":"2026-02-10 15:52:10","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":788667,"visible":true,"origin":"","legend":"\u003cp\u003eSpatial distribution of scalloped hammerhead shark sightings recorded by drones at Burleigh Beach and Noosa Main Beach, respectively. A) Kernel density heatmap of shark tracks from 2023; B) Kernel density heatmap from 2024, C) Kernel density heatmap from 2023 at Noosa Main Beach. Yellow areas indicate higher sightings densities, while purple areas indicate lower densities. Heatmap scales (A: 0-116,852; B: 0-60,664; C: 0-12,597) represent relative intensity of overlap derived from kernel density estimation, not absolute sighting counts.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/050f7cf03b26b03712497332.png"},{"id":102334380,"identity":"efd5e7c9-7772-4461-bf04-5b2840539f07","added_by":"auto","created_at":"2026-02-10 15:52:10","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":83249,"visible":true,"origin":"","legend":"\u003cp\u003eInfluence of significant predictor variables on the probability of sighting scalloped hammerhead shark across all southeast Queensland beaches: (A) turbidity, (B) sea state, (C) presence of other fauna, (D) flight number (time of day), (E) month, and (F) location. Solid black lines represent model-fitted values, and grey shaded areas indicate 95% confidence intervals.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/ee4df0c3010f00f68b8b6788.png"},{"id":102399039,"identity":"3509bd69-8fd3-4210-afb6-e7cf5059a4fc","added_by":"auto","created_at":"2026-02-11 10:32:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5018257,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/67179570-7c66-4f8e-95a6-85d8af0f2187.pdf"},{"id":102334381,"identity":"e2f62222-b6de-472d-9378-756c21dd3861","added_by":"auto","created_at":"2026-02-10 15:52:10","extension":"pdf","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":195227,"visible":true,"origin":"","legend":"","description":"","filename":"ESM1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8769949/v1/dafe4a2551a1812b64f33772.pdf"}],"financialInterests":"","formattedTitle":"Drone monitoring of endangered scalloped hammerhead shark Sphyrna lewini movements and habitat use on a dynamic urbanised coastline in Australia","fulltext":[{"header":"Introduction","content":"\u003cp\u003eUnderstanding the movements and habitat use of endangered marine species is fundamental to their conservation, as it informs spatial management and the protection of critical life stages such as breeding, nursery and aggregation sites. However, monitoring marine megafauna in dynamic coastal environments remains a significant challenge due to factors such as turbidity, complex bathymetry, and the logistical and cost constraints of traditional survey methods limiting data availability (Butcher et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Cross et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Elasmobranchs (sharks and rays) can be particularly vulnerable to anthropogenic pressures in these coastal areas, including overfishing, habitat degradation, and rapid urban development (Dulvy et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Pacoureau et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Urban-driven alterations to these habitats can disrupt key behaviours in elasmobranchs, including foraging, migration, and parturition (Heupel et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Todd et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Given their proximity to these areas, many coastal species are facing significant global population declines, and key aspects of their movement ecology and habitat use remain poorly understood, complicating efforts to develop targeted conservation and management strategies.\u003c/p\u003e \u003cp\u003eAmong the more imperilled species, scalloped hammerhead sharks (\u003cem\u003eSphyrna lewini\u003c/em\u003e) have undergone steep population declines worldwide, with estimates exceeding 80% (Pacoureau et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Lopez et al. 2023). As a result, the International Union for Conservation of Nature (IUCN) classified the species as Critically Endangered under criterion A2bd (Rigby et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), which reflects an estimated median global population reduction of 76.9\u0026ndash;97.3% over three generation lengths (72.3 years). They are also listed in Appendix ІІ of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).\u003c/p\u003e \u003cp\u003eWhile global populations continue to decline, Australia\u0026rsquo;s relatively healthy stocks position it as a \u0026lsquo;lifeboat\u0026rsquo; nation, offering both a refuge for the species and a valuable opportunity for conservation research. Within Australia, they are listed as \u0026lsquo;Conservation Dependent\u0026rsquo; under the \u003cem\u003eEnvironment Protection and Biodiversity Conservation Act 1999\u003c/em\u003e (EPBC ACT 2018) and they have been a no-take species in Queensland waters since 2024 (Queensland Government \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). To support effective conservation strategies, there is an urgent need to identify critical habitats, including breeding, parturition, nursery, and aggregation sites, particularly in regions like Australia, where the species remains accessible for study, and to apply these insights to areas where populations have been severely depleted or extirpated.\u003c/p\u003e \u003cp\u003eScalloped hammerheads have a circumglobal distribution, inhabiting tropical and warm temperate waters (Compagno \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). This species is highly mobile, capable of migrating over 1,000 km (Bessudo et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Spaet et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and occurs across a mosaic of ecosystems, including, estuaries, bays, continental shelfs, and offshore pelagic waters (Wells et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Despite their migratory capacity, studies have found that most scalloped hammerheads have relatively small home ranges and display aggregative behaviours around bathymetric features, such as seamounts, likely influenced by environmental factors (Klimley et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Holland et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Hearn et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Bessudo et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Lopez et al. 2023). These aggregations are subject to sexual segregation, with adult males and females typically occupying different spatial regions within their overall distribution (Klimley \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Stevens and Lyle \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Mature females, although rarely observed, are believed to primarily inhabit offshore, pelagic waters, whereas males tend to remain closer to coastal areas (Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Hoyos-Padilla et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Wells et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). During warmer summer months, pregnant females are thought to migrate inshore to give birth, typically producing litters of 10 to 14 pups (Stevens and Lyle \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Neonates and juveniles are predominantly found in shallow, turbid coastal nursery areas, where they remain for several months (Simpfendorfer and Milward \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Yates et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Brown et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Zanella et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Scalloped hammerhead pups are born at sizes ranging from approximately 31 to 57 cm in total length, with sexual maturity attained at lengths of around 140\u0026ndash;198 cm for males and 200\u0026ndash;250 cm for females, and maximum sizes reaching up to 430 cm (Ebert et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, knowledge gaps remain in Australia regarding their seasonal habitat preferences, the duration of their stay in nursery areas, and their subsequent movements after leaving these regions (Simpfendorfer and Milward \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Duncan and Holland \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Hutchinson et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eUnmanned Aerial Vehicles (UAVs; hereafter referred to as \u0026lsquo;drones\u0026rsquo;) offer a unique vantage point for observing marine megafauna and have been increasingly used in recent years to identify important habitats for elasmobranchs (Raoult et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Ayres et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Drones are especially advantageous for shark research, providing non-invasive monitoring with minimal disturbance to the species, a critical consideration for understanding natural behaviour and movements (Butcher at al. 2021; McIvor et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Cross et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Studies have demonstrated the utility of drones in detecting sharks off coastal beaches (Kelaher et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Mitchell et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022b\u003c/span\u003e; Cross et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), highlighting their potential for detecting the presence of scalloped hammerhead sharks. This is emphasised in a recent study by Lopez et al. (2022), which used drones to monitor a seasonal scalloped hammerhead aggregation in Western Australia. The study documented aggregation size and structure, behavioural interactions, and environmental drivers influencing the timing and presence. This aggregation extended the southern range of the species in Australia, and the findings were used to make recommendations for improved coastal zone management and marine park planning, supporting the need for protection of this aggregation site (Lopez et al. 2023).\u003c/p\u003e \u003cp\u003eSince September 2020, the Queensland SharkSmart drone program has monitored sharks for public safety purposes at up to nine beaches in southeast Queensland, Australia (Mitchell et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2022a\u003c/span\u003e; Mitchell et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The program has recorded a total of 4,959 sharks from September 2020 to April 2024, across 16,601 flights (Mitchell et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). A range of environmental and biotic factors were found to influence shark sightability, including the sighting of other fauna, season, wind speed and direction, turbidity, tidal state, glare, and atmospheric pressure (Mitchell et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The archived footage represents an important resource for documenting marine megafauna biodiversity, abundance, and behaviour. This study used the archived footage from the Queensland SharkSmart drone program to assess sightings of scalloped hammerhead sharks off coastal beaches of southeast Queensland between September 2020 to December 2024. Specifically, the objectives of this study were to identify how frequently scalloped hammerhead sharks were sighted off these coastal beaches and quantify the influence of environmental, biotic, and operational factors on their sightability. Additionally, this study aimed to determine the presence of important habitats for the species, such as those supporting aggregations and juveniles.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e\u003cstrong\u003eStudy site and drone flights\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFrom 2020 to 2024, the Queensland SharkSmart drone program operated at nine beach locations in southeast Queensland (Fig. 1), as described in Mitchell et al. (2025). Pilots from Surf Life Saving Queensland fly drone surveys on weekends, public holidays, and school holidays when weather permits, completing 8-10 flights per day between 07:00 and 12:00. Flight transects were 400 m long behind the surf break (~200 m offshore), with multiple passes of the transect occurring (Fig. 2; Cross et al. 2024). Drone footage was recorded in 4k high definition and archived for later analysis. Shark sightings were recorded, including an estimate of animal total length, direction of movement, and proximity to the beach. A range of environmental variables were also recorded for each flight (Table 1; Mitchell et al. 2025). Species could only be determined for distinctive species, including white shark (\u003cem\u003eCarcharodon carcharias\u003c/em\u003e), tiger shark (\u003cem\u003eGaleocerdo cuvier\u003c/em\u003e), bull shark (\u003cem\u003eCarcharhinus leucas\u003c/em\u003e), and leopard shark (\u003cem\u003eStegostoma tigrinum).\u0026nbsp;\u003c/em\u003eIn other cases, sharks were recorded into categories including whaler sharks (\u003cem\u003eCarcharhinus\u0026nbsp;\u003c/em\u003espp.) and hammerhead sharks at initial classification. This species complex could therefore include any scalloped (\u003cem\u003eSphyrna lewini\u003c/em\u003e), great (\u003cem\u003eS. mokarran\u003c/em\u003e) or smooth (\u003cem\u003eS. zygaena\u003c/em\u003e) hammerheads, based on their distribution (Compagno 1984). Further species-specific identification was confirmed using high-resolution stills extracted from the footage, focusing on clear images of individuals swimming close to the surface that displayed distinctive morphological features, including a scalloped cephalofoil (head shape) and central indentation (Fig. 3). All confirmed sightings were scalloped hammerheads (\u003cem\u003eS. lewini\u003c/em\u003e). Therefore, other species were omitted from the dataset based on these clear morphological distinctions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Environmental, biotic, and operational factors included in the Generalised Additive Models (GAMs) to assess the likelihood of sighting scalloped hammerhead sharks.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eFactor Type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eFactor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eUnit of measurement/notes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eMonth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eJanuary-December\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eRainfall\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003emm/day\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eAir temperature\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003e\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eTurbidity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003e0-100 %\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eSea state\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eBeaufort Scale (low =1, high = 12)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eWind speed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003ekm h\u0026minus;1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eCloud cover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eOktas\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eGlare\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003e1 (low)-5(high) scale\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eEnvironmental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eAtmospheric pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003ehPa\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eBiotic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003ePresence of other fauna\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eBait balls, fish, rays, marine mammals\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eOperational\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eLocation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eBeach\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 23px;\"\u003e\n \u003cp\u003eOperational\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29px;\"\u003e\n \u003cp\u003eFlight number (time of day)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 46px;\"\u003e\n \u003cp\u003eFlight number (1-8)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eData collection for scalloped hammerhead sharks\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor each sighting, species, number of animals present, presence of other fauna, and the sharks\u0026rsquo; movement track were recorded. Movement tracks were generated using QGIS (v3.32.2-Lima; 2023; see Cross et al. 2025 for track methods). Movement tracks recorded represent the flight path of the drone\u0026rsquo;s position rather than the precise movements of the sharks. To ensure accuracy, only instances where the drone was closely aligned above the shark were included in analysis. Previous research by Raoult et al. (2018) demonstrated that drones flown directly overhead can provide highly precise trajectory data for sharks. However, in cases involving large schools of sharks, the tracks reflect general activity and fine-scale habitat use patterns rather than the directional movements of individual animals, due to difficulty distinguishing individuals within aggregations.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo account for differences in survey effort among locations, the total number of flights at each site was converted into effort hours (two flights per hour), and sighting rates were calculated as the number of hammerhead shark events or individuals per flight hour.\u003c/p\u003e\n\u003cp\u003eTotal length of each scalloped hammerhead shark was estimated by comparing the shark\u0026rsquo;s size to nearby reference objects visible in the footage, such as swimmers, surfboards, paddleboards, and other marine animals (Fig. 4). For paddleboards, an average length of 3.15 m (range: 2.8 \u0026ndash; 3.5 m) was used based on standard dimensions. Shark length was estimated by assessing the relative size of the shark to the reference object within the same frame (Graham and Roberts 2007). In instances where no reliable scale objects were present, footage from the same area and day when reference objects were available, was used to approximate scale. If no suitable reference could be established, the shark was excluded from length analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eKernel Density Estimation (KDE) heatmaps of individual scalloped hammerhead shark tracks were generated using QGIS. Only Burleigh Beach and Noosa Main Beach were selected due to high shark sighting frequencies and clear recurring patterns of use. KDE analysis was conducted by interpolating shark track points into a heatmap using a 10 m cell size, following methods outlined in Cross et al. (2025).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA Generalised Additive Model (GAM) was used to quantify the influence of environmental, biotic, and operational factors on the likelihood of observing scalloped hammerhead sharks (Table 1). Presence or absence of scalloped hammerhead sharks was used as the response with a binomial distribution. To account for the vastly different number of flights conducted at each location and differences in scalloped hammerhead sightings, location was included as a random effect in the model. Prior to model fitting, Pearson correlation coefficients were calculated for continuous predictor variables to identify and avoid multicollinearity; any pairs with a correlation coefficient greater than 0.5 were not used in the same model. The distribution of predictor variables were visually inspected, and where distributions were skewed, square root or log(x+1) transformations were applied. Model selection was performed using a backward stepwise approach, sequentially removing individual predictor variables and monitoring changes in the Akaike Information Criterion (AIC; Akaike 1974). The final model was selected based on the lowest AIC value and inclusion of only statistically significant predictor variables. All statistical analyses were conducted in RStudio (R v4.4.1; RStudio v1.4.1711; R Core Team 2023). The \u003cem\u003emgcv\u003c/em\u003e package (v1.9.3; Wood 2017) was used to build GAMs, and the \u003cem\u003etidyverse\u003c/em\u003e package (v1.3.2; Wickham et al. 2019) was used for data organisation and visualisation.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eScalloped hammerhead sightings\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAcross the nine southeast Queensland beaches monitored by the SharkSmart drone program, a total of 90 scalloped hammerhead shark sighting events were recorded from the 20,911 drone flights between September 2020 to December 2024, comprising 2,696 individual sharks in total. The majority of sightings occurred at Burleigh Beach (Gold Coast) and Noosa Main Beach (Sunshine Coast), where sighting rates were highest (0.026 and 0.032 events/hr, and 1.105 and 1.015 individuals/hr, respectively; Table 2). Many sharks at these locations were likely resighted across multiple flights, and as such, this figure does not represent the total number of unique individuals. Sightings at Burleigh and Noosa almost exclusively involved groups of multiple animals, whereas other beaches generally involved solitary individuals or pairs (Table 2). Group size ranged from one to 100 individuals, and estimated total lengths varied from \u0026lt;0.80 m to 3 m (mean \u0026plusmn; SD: 109 \u0026plusmn; 25 cm; Fig. S1). Juveniles dominated sightings at Burleigh and Noosa, while larger individuals were more frequently observed off North Stradbroke Island.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2.\u003c/strong\u003e Summary of scalloped hammerhead shark sightings across nine southeast Queensland beach locations covered by the SharkSmart drone program, including standardised sighting events.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"left\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eBeach location\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003eNo. of flights\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003eNo. of hammerhead sighting events\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eNo. of individuals\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eSighting rate (events/hr)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eIndividuals/hr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003eTotal length (TL) range (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003eGroup size range\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eAlexandra Headlands\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e3,277\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u0026lt;100\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eBribie Island\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e1,183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e100 - 200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eBurleigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e3,091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1,708\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1.105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e0.80 - 150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e1 - 80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eCoolum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e3,008\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eKurrawa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e1,730\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eNoosa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e1,907\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e968\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.032\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u0026lt;100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e1 - 100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eNorth Stradbroke Island\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e1,885\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e150 - 300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e1 - 2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eRainbow Beach\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e1,787\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003eSouthport\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e3,043\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e100 - 250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e1 - 2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e20,911\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2,696\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.009\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.258\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.80 - 300\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 9px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1 - 100\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003csup\u003ea\u003c/sup\u003e Includes repeated sightings of the same individuals\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMovement patterns and space use\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eScalloped hammerhead sharks displayed variable movement patterns and space use off the surveyed coastal beaches. At North Stradbroke Island (Fig. 5A), 13 of the 14 sharks moved northeast parallel to the shoreline, following linear trajectories with minimal deviation in direction. Most individuals were tracked for approximately 100 m, although one shark was tracked for approximately 250 m. The remaining individual also exhibited a linear trajectory but travelled eastward. In contrast, observations at Burleigh Beach revealed more clustered movement patterns, particularly during aggregations between March and early June (Fig. 5B). Tracks from 1 April 2023 (yellow) and 3\u003csup\u003e\u0026nbsp;\u003c/sup\u003eApril 2024 (red) showed frequent overlap and repeated use of the same coastal areas, with each track representing movements of multiple scalloped hammerheads observed on a single drone flight during the aggregation period. Kernel density heatmaps revealed consistent spatial hotspots at Burleigh across both years (Figs. 6A and 6B), with sightings concentrated near the southern end of Burleigh Beach near Burleigh Headland. A similar pattern of localised space use was evident at Noosa Beach from 6 April to 30 June 2023 (Fig. 6C). However, scalloped hammerheads were not observed at Noosa during the same period in 2024, unlike the persistent aggregations observed at Burleigh Beach. During the 2023 aggregation season, shark presence was documented in three main areas. The central hotspot, adjacent to Noosa Main Beach, showed the highest sighting density, with two additional zones of moderate activity extending to the east and west.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFactors influencing hammerhead shark presence\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe best ranked model with the lowest AIC value identified turbidity, presence of other fauna, sea state, flight number (proxy for time of day), month and location as significant predictors of hammerhead shark sightability (Table S1). These variables collectively explained 33% of the deviance in the response variable (Tjur\u0026rsquo;s R\u0026sup2; = 0.094; Table S2). Sightings were negatively associated with increasing turbidity (Fig. 7A) and higher sea states (Fig. 7B), with the highest probability of sightings observed in clear (0.015 \u0026plusmn; 0.007) and calm (0.011 \u0026plusmn; 0.005) conditions. The presence of other fauna significantly increased the likelihood of hammerhead sightings (0.015 \u0026plusmn; 0.006; Fig. 7C). Within the morning survey period, the probability of sightings declined over time, with earlier flights sighting significantly more sharks (0.005 \u0026plusmn; 0.002; Fig. 7D). Temporal analysis revealed a seasonal pattern, with peak sighting probabilities occurring between April (0.011 \u0026plusmn; 0.005) and June (0.005 \u0026plusmn; 0.002), and lower probabilities recorded during the summer months (0.001 \u0026plusmn; 0.001; Fig. 7E). Spatial variation in sightings was evident, with the highest probabilities of hammerhead presence observed at Burleigh (0.013 \u0026plusmn; 0.005) and Noosa (0.012 \u0026plusmn; 0.005) beaches (Fig. 7F).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study highlights drones as a highly effective, non-invasive tool for detecting fine-scale habitat use of scalloped hammerhead sharks (\u003cem\u003eSphyrna lewini\u003c/em\u003e). Here, we demonstrate the successful detection of spatio-temporal hammerhead aggregations at popular urbanised beach sites that serve as important habitat for these juveniles at this critical life history stage. Further, these sharks were previously undetected at these same locations through traditional monitoring programs, indicating the viability of deploying UAVs as an emerging tool for research on critically endangered elasmobranchs.\u003c/p\u003e \u003cp\u003eThe repeated detection of juvenile scalloped hammerheads, particularly in large aggregations at Burleigh and Noosa, suggests that these sites may provide critical habitat features that enhance survival and growth, such as abundant prey, structural refuge, and reduced predation risk (Brown et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In contrast, the predominance of solitary individuals at Bribie Island, North Stradbroke Island, and Southport Main Beach highlights fine-scale spatial heterogeneity in habitat suitability, indicating that juveniles may actively partition space to balance resource acquisition with predator avoidance. These spatial patterns align with observations from the Eastern Tropical Pacific (including Colombia and the Galapagos Islands) and Central Pacific (Hawaii), where scalloped hammerheads exhibit strong site selectivity (Hearn et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Bessudo et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) and occupy small core areas during daylight hours (Klimley et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Holland et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Collectively, these findings suggest that juvenile scalloped hammerheads are not randomly distributed but instead exhibit strategic habitat selection influenced by a combination of biotic and abiotic factors, including prey availability, refugia, and local environmental conditions.\u003c/p\u003e \u003cp\u003eAlthough the observed individuals comprised a mix of young-of-the-year and older juveniles (1\u0026ndash;2 years old; Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Lubitz et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) rather than neonates, the repeated occurrence of similar sized sharks across multiple months and years suggests seasonal and interannual use of these areas. While these coastal zones may not meet the criteria for nursery areas as defined by Heupel et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), they likely serve as important juvenile aggregation areas. Notably, the sampled beaches are located within 20\u0026ndash;60 km of several estuarine and embayment systems, including Moreton Bay, Broadwater, and associated river mouths, which have been proposed as potential nursery grounds for scalloped hammerheads in this region (Gustafson \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The presence of older juveniles at coastal beach sites may therefore reflect an ontogenetic shift in habitat use, with individuals dispersing from sheltered nursery areas as their energetic requirements and prey preferences change with development.\u003c/p\u003e \u003cp\u003eAggregations occurred consistently between March and June, which overlaps with the known regional pupping season for scalloped hammerhead sharks (Stevens and Lyle \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Gustafson \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), although the individuals observed during this period were likely born in previous years. This seasonal timing may still be ecologically significant, as warmer water temperatures during these months can increase prey availability and support elevated metabolic and growth rates in juveniles (Simpfendorfer and Milward \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Duncan and Holland \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Niella et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These conditions may make adjacent coastal habitats particularly favourable for older juveniles during this time of year. Together, these findings support the hypothesis that coastal zones act as transitional developmental habitats and underscore the need for long-term monitoring, particularly through acoustic telemetry, to confirm connectivity with nearby nurseries and identify the environmental drivers shaping juvenile distribution.\u003c/p\u003e \u003cp\u003eMovement patterns varied across locations, reflecting differences in how scalloped hammerhead sharks use coastal habitats across different life stages and regions. At North Stradbroke Island, scalloped hammerheads displayed linear, directed trajectories consistent with transitory movements by larger individuals (Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Wells et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Given its proximity to the continental shelf (~\u0026thinsp;23 km; Cross et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), this location may serve as a navigational aid during seasonal migrations (Klimley \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Holmes et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), particularly for mature scalloped hammerhead females moving towards the coast in summer and autumn. While these inshore movements coincide with periods of reproductive activity reported in eastern Australia and the broader Indo-Pacific (Stevens and Lyle \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Harry et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), the absence of long-term tracking data limits their interpretation as definitive reproductive migrations. Additionally, North Stradbroke Island lies within the influence of the East Australian Current (EAC), which brings warmer tropical waters during summer months (Suthers et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). This temperature variation may further influence seasonal movement patterns, with larger sharks potentially following thermal gradients for energetic efficiency or reproductive cues (Niella et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The use of adjacent shallow areas may also provide thermal benefits or protection during these transits, although further research is needed to confirm the drivers of these movements (Holland et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Klimley \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1993\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn contrast, juveniles at Burleigh Beach and Noosa Main Beach exhibited highly localised movements in shallow nearshore areas. At Burleigh, a rocky headland habitat appears to be a focal congregation point, suggesting that site fidelity may be driven by structural complexity, which supports higher prey abundance and diversity by providing both shelter and foraging opportunities for lower trophic levels (Ketchum et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Yates et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Brown et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). While aggregations of juvenile scalloped hammerheads have been rarely documented in Australian waters (Klimley \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; Lopez et al. 2023; Lubitz et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), the repeated overlap of movements tracks at Burleigh across multiple years underscores its importance as an aggregation site. Such behaviour may reflect schooling for predator avoidance or improved foraging efficiency. Notably, core use areas ranged from 0.2 km\u003csup\u003e2\u003c/sup\u003e to 0.4 km\u003csup\u003e2\u003c/sup\u003e, closely matching the 0.2 km\u003csup\u003e2\u003c/sup\u003e core aggregation area reported in scalloped hammerhead sharks in Western Australia (Lopez et al. 2023), highlighting the critical role of small, localised habitats in supporting juveniles. These aggregations resemble those documented in the eastern Pacific, where juveniles display site-specific behaviours including resting and repeated co-occurrence, which may suggest social interactions (Klimley \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; Klimley \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Ketchum et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Papastamatiou et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eScalloped hammerhead sightability was significantly influenced by environmental and operational variables. Visibility factors such as turbidity and sea state reduced sighting probability, consistent with previous drone-based elasmobranch studies (Raoult et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Cross et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Mitchell et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). These conditions not only limit aerial visibility but may influence shark behaviour, possibly reducing surface time or nearshore presence during rough conditions. Nonetheless, sharks may still be present under such conditions but remain undetected. In contrast, sightings increased when bait balls and teleosts were present, suggesting shared habitat use or foraging in productive zones, although reduced detectability under conditions of high turbidity or rough sea state may also have contributed. Given their diet of benthic teleosts and cephalopods (Rosende-Pereiro et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Galloway et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; P\u0026aacute;ez-Rosas et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), this likely reflects prey-driven habitat selection. Estuarine outflows from nearby Tallebudgera Creek (Burleigh Beach) and the Noosa River (Noosa Main Beach) may enhance local productivity and prey abundance, contributing to consistently high hammerhead sightings (Meynecke et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Connolly et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Additionally, the presence of nearby reefs such as Burleigh Reef and Palm Beach Reef, both adjacent to Burleigh Beach, may provide structurally complex habitats that support diverse prey communities, further attracting scalloped hammerheads to this area (Henderson et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTemporal patterns were also observed, with sightings more frequent during early morning flights, consistent with crepuscular activity in juveniles (Klimley et al. 1998; Bush \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). However, surveys were restricted to morning hours, leaving much of the diel cycle unsampled and limiting broader temporal inference. The observed patterns are likely primarily driven by crepuscular foraging and movement behaviours, which are widely documented in scalloped hammerhead sharks (Klimley et al. 1998; Bush \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Ketchum et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Lopez et al. 2023). Increasing human activity later in the morning may also contribute to reduced sighting rates, as sharks were observed avoiding snorkellers and paddle boarders, with aggregations occasionally disrupted. These behavioural responses align with studies reporting stress or site abandonment in elasmobranchs exposed to anthropogenic activity (Barker et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Trave et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Cattano et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Seasonally, sightings peak between April and June, potentially linked to prey availability, as well as seasonal changes in the EAC, including both its strengthening and meanders, which can influence local oceanographic conditions (Suthers et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Niella et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Parturition, often occurring in warmer summer months in adjacent coastal embayments, may also contribute to seasonal peaks in abundance as these juveniles appear in these nearshore waters a few months later in the austral Autumn period (Simpfendorfer and Milward \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Duncan and Holland \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Hutchinson et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Collectively, spatiotemporal trends suggest hammerhead presence is shaped by ecological productivity and habitat complexity, patterns observed not only in juvenile aggregations documented in southwest Western Australia (Lopez et al. 2022) but also around oceanic islands and seamounts in the Eastern Tropical Pacific (Hearn et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Bessudo et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eImplications for conservation and monitoring\u003c/h2\u003e \u003cp\u003eFindings reported herein support the use of drones for targeted monitoring of endangered elasmobranchs. Importantly, the absence of escape or erratic responses indicates minimal disturbance to these sharks from drones, supporting their reliability and ongoing use for behavioural monitoring (Butcher et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Mitchell et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022b\u003c/span\u003e). Drone-derived data offer a pathway for adaptive management, enabling dynamic, seasonally informed mitigation strategies that enhance both public safety and conservation outcomes. These insights can support marine spatial protections, including the designation of Essential Fish Habitat (EFH) under national legislation, and internationally, Important Shark and Ray Areas (ISRAs; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://sharkrayareas.org/about-isras/\u003c/span\u003e\u003cspan address=\"https://sharkrayareas.org/about-isras/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) to protect key habitats for sharks and rays. Moreover, drone observations can engage the public by presenting sharks in a natural context, potentially shifting perceptions and building support for conservation (Stokes et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Cross et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). These data can also inform the development and promotion of codes of practice aimed at minimising human disturbance during shark interactions.\u003c/p\u003e \u003cp\u003eWhile drones improve our ability to monitor these populations and inform management, existing human activities continue to impact these species. The high juvenile presence at Burleigh Beach and Noosa Main Beach highlights the need for seasonal spatial protections. However, both sites are part of the Queensland Government's Shark Control Program (QSCP) which aims to reduce the risk of shark bites using a combination of operational equipment (shark nets, baited drumlines, drones), research, trials and education. At Noosa, both shark nets and baited drumlines are operated, while Burleigh is equipped with shark nets only, which are located 300\u0026ndash;500 m offshore. Between 2001 and 2024, the QSCP recorded 65 captures of scalloped hammerheads at Burleigh and Noosa combined, 63 in nets and two on drumlines, comprising both juveniles and adults (Queensland Department of Primary Industries 2025). Statewide, 675 scalloped hammerheads were captured over the same period, including 512 in nets and 163 on drumlines. Although not a target species, scalloped hammerheads are particularly susceptible to fishing mortality, and all but 10 individuals caught under the QSCP were deceased.\u003c/p\u003e \u003cp\u003eJuvenile captures (\u0026lt;\u0026thinsp;120 cm) peak from September to February, coinciding with presumed nursery use, yet drone surveys documented aggregations from March to June, revealing a temporal mismatch. This discrepancy may reflect seasonal variation in depth and habitat use, with juveniles typically occupying surface waters and adults occurring closer to the seafloor (Lopez et al. 2023). The QSCP\u0026rsquo;s surface-set nets, which feature relatively large mesh sizes (~\u0026thinsp;500 mm), likely influence the size classes caught. Most scalloped hammerheads recorded are \u0026lt;\u0026thinsp;200 cm in total length, indicating that juveniles and subadults are more susceptible to entanglement. Additionally, the offshore positioning of nets (~\u0026thinsp;500 m from shore) may provide some spatial separation from inshore juvenile aggregations, further contributing to the mismatch between observed presence and recorded captures.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eLimitations and future directions\u003c/h2\u003e \u003cp\u003eDespite their utility, drones have inherent limitations. Drones cannot distinguish individual sharks (unless the animal has clearly distinctive markings or injuries), meaning repeated sightings may represent the same individuals. Their effectiveness is also constrained by favourable weather, water clarity, and depth, particularly because drone-based observations are typically limited to shallow (\u0026lt;\u0026thinsp;5 m), clear-water environments. This introduces a detection bias, as other potential aggregation sites in deeper or turbid waters may go undetected. Improvements such as polarising filters (Butcher et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), machine learning-assisted detection (Butcher et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), and geometric photogrammetry (Rex et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) could enhance the ability of drones to detect sharks in suboptimal conditions and demographic assessments. Future integration with acoustic telemetry, environmental DNA (eDNA) sampling, and photo-ID would support a more comprehensive understanding of site fidelity, population dynamics, and habitat connectivity, ultimately strengthening conservation outcomes.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003ch2\u003eEthics approval\u003c/h2\u003e\n\u003cp\u003eThis is an observational study. The Queensland Government has confirmed that no ethical approval is required.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eAlthough this research did not receive external funding, the SharkSmart drone program is funded by the Queensland Government.\u003c/p\u003e\n\u003ch2\u003eAuthor contributions\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection, analysis, and data curation were performed by Maddison Cross. Methodology and software development were carried out by Maddison Cross, Tracey Scott-Holland, and Jonathan Mitchell. Validation was performed by all authors. Supervision was provided by Bonnie Holmes, Matthew McMillan, Johan Gustafson, and Jonathan Mitchell. The first draft of the manuscript was written by Maddison Cross, and all authors contributed to reviewing and editing subsequent versions. Project administration was led by Maddison Cross and Jonathan Mitchell. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgements\u003c/h2\u003e\n\u003cp\u003eThe authors would like to thank the Surf Life Saving Queensland drone pilots for their role in collecting footage and data for the SharkSmart drone program. Gratitude is also extended to Rob Adsett, Greg Cahill, Damien Boyer and other staff members from Surf Life Saving Queensland for their support with logistics, project management, and administration. The authors thank Dr. Paul Butcher from the New South Wales Department of Primary Industries and Regional Development, along with Dr. Andrew Colefax and Dr. Justin Meager, for their scientific advice on the design and implementation of the Queensland SharkSmart drone program. The Queensland Government is acknowledged for funding all beach drone operations as part of the SharkSmart drone program. This research was supported by an Australian Government Research Training Program (RTP) Scholarship, the Queensland DPI Charter and Commercial Fishing Grant, and the Winifred Violet Scott Charitable Trust.\u003c/p\u003e\n\u003ch2\u003eData availability\u003c/h2\u003e\n\u003cp\u003eCorres. author can provide the datasets used in this study upon reasonable request, although footage which contains images of people is considered confidential and cannot be made publicly available.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAkaike H (1974) A new look at the statistical model identification. IEEE Transactions on Automatic Control 19:716\u0026ndash;723.\u003c/li\u003e\n\u003cli\u003eAyres KA, Ketchum JT, Gonz\u0026aacute;lez-Armas R, Galv\u0026aacute;n-Maga\u0026ntilde;a F, Hearn A, Elorriaga-Verplancken FR, Hoyos-Padilla EM, Kajiura SM (2021) The use of an unoccupied aerial vehicle to survey shark species over sand and rocky-reef habitats in a marine protected area. J Fish Biol 99:1735\u0026ndash;1740. https://doi.org/10.1111/jfb.14838\u003c/li\u003e\n\u003cli\u003eBarker SM, Peddemors VM, Williamson JE (2011) A video and photographic study of aggregation, swimming and respiratory behaviour changes in the grey nurse shark (\u003cem\u003eCarcharias taurus\u003c/em\u003e) in response to the presence of SCUBA divers. Mar Freshw Behav Physiol 44:75\u0026ndash;92. https://doi.org/10.1080/10236244.2011.569991\u003c/li\u003e\n\u003cli\u003eBessudo S, Soler GA, Klimley AP, Ketchum JT, Hearn A, Arauz R (2011) Residency of the scalloped hammerhead shark (\u003cem\u003eSphyrna lewini\u003c/em\u003e) at Malpelo Island and evidence of migration to other islands in the eastern tropical Pacific. Environ Biol Fish 91:165\u0026ndash;176. https://doi.org/10.1007/s10641-011-9769-3\u003c/li\u003e\n\u003cli\u003eBrown K, Seeto J, Lal M, Miller C (2016) Discovery of an important aggregation area for endangered scalloped hammerhead sharks, \u003cem\u003eSphyrna lewini\u003c/em\u003e, in the Rewa River estuary, Fiji Islands. Pac Conserv Biol 22:242\u0026ndash;248. https://doi.org/10.1071/PC14930\u003c/li\u003e\n\u003cli\u003eBush A (2003) Diet and diel feeding periodicity of juvenile scalloped hammerhead sharks, \u003cem\u003eSphyrna lewini\u003c/em\u003e, in Kāne\u0026lsquo;ohe Bay, Ō\u0026lsquo;ahu, Hawai\u0026lsquo;i. Environ Biol Fish 67:1\u0026ndash;11. https://doi.org/10.1023/A:1024438706814\u003c/li\u003e\n\u003cli\u003eButcher PA, Colefax AP, Gorkin RA, Kajiura SM, L\u0026oacute;pez NA, Mourier J, Purcell CR, Skomal GB, Tucker JP, Walsh AJ, Williamson JE, Raoult V (2021) The drone revolution of shark science: a review. Drones 5:8. https://doi.org/10.3390/drones5010008\u003c/li\u003e\n\u003cli\u003eButcher P, Piddocke T, Colefax A, Hoade B, Peddemors V, Borg L, Cullis B (2019) Beach safety: can drones provide a platform for sighting sharks? Wildl Res 46:701\u0026ndash;712. https://doi.org/10.1071/WR18119\u003c/li\u003e\n\u003cli\u003eCattano C, Turco G, Di Lorenzo M, Gristina M, Visconti G, Milazzo M (2021) Sandbar shark aggregation in the central Mediterranean Sea and potential effects of tourism. Aquat Conserv Mar Freshw Ecosyst 31:1420\u0026ndash;1428. https://doi.org/10.1002/aqc.3517\u003c/li\u003e\n\u003cli\u003eCompagno LJV (1984) FAO species catalogue, Vol 4: sharks of the world. An annotated and illustrated catalogue of shark species known to date, Part 2: Carcharhiniformes. FAO Fish Synop 125:251\u0026ndash;655\u003c/li\u003e\n\u003cli\u003eConnolly RM, Schlacher TA, Gaston TF (2009) Stable isotope evidence for trophic subsidy of coastal benthic fisheries by river discharge plumes off small estuaries. Mar Biol Res 5:164\u0026ndash;171. https://doi.org/10.1080/17451000802266625\u003c/li\u003e\n\u003cli\u003eCross MC, Mitchell JD, Dudgeon CL, Townsend KA, Scott-Holland TB, Holmes BJ (2024) Spatial and temporal variation of marine megafauna off coastal beaches of south-eastern Queensland, Australia. Mar Freshw Res 75:MF24094. https://doi.org/10.1071/MF24094\u003c/li\u003e\n\u003cli\u003eCross M, Mitchell J, Scott-Holland T (2025) High-resolution mapping of shark movements from drone footage at Queensland beaches improves risk assessment for beach safety. 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Environ Biol Fish 102:1291\u0026ndash;1300. https://doi.org/10.1007/s10641-019-00907-1\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"marine-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mabi","sideBox":"Learn more about [Marine Biology](https://www.springer.com/journal/227)","snPcode":"227","submissionUrl":"https://submission.nature.com/new-submission/227/3","title":"Marine Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"aerial surveys, spatial ecology, critical habitat, juvenile sharks, elasmobranchs","lastPublishedDoi":"10.21203/rs.3.rs-8769949/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8769949/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMany elasmobranch species face increasing pressures from overfishing, habitat degradation, and coastal development, yet their movement ecology remains poorly understood. Unmanned Aerial Vehicles or drones offer a non-invasive method to study the distribution and habitat use of species frequenting inshore areas. Scalloped hammerhead sharks (\u003cem\u003eSphyrna lewini\u003c/em\u003e), listed as Critically Endangered on the International Union for the Conservation of Nature (IUCN) Red List, have experienced global population declines prompting the need for research that identifies key habitats, including nursery and aggregation sites. This study analysed archived footage from the Queensland SharkSmart drone program at nine beaches in southeast Queensland between September 2020 and December 2024. The frequency of scalloped hammerhead sightings was quantified, along with the influence of environmental, biotic, and operational variables on sightability. Ninety sightings were recorded, primarily between April and June. Sightings were significantly influenced by turbidity, presence of other fauna, time of day, month, and location. Aggregations of up to 80 juvenile sharks (estimated mean total length 109 cm\u0026thinsp;\u0026plusmn;\u0026thinsp;25 cm) were observed at Burleigh Beach, with additional sightings at Noosa Main Beach. These findings provide new insights into the species\u0026rsquo; spatial ecology in southeast Queensland, Australia and demonstrate the value of drone monitoring for conservation and spatial management.\u003c/p\u003e","manuscriptTitle":"Drone monitoring of endangered scalloped hammerhead shark Sphyrna lewini movements and habitat use on a dynamic urbanised coastline in Australia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-10 15:52:05","doi":"10.21203/rs.3.rs-8769949/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-02-05T15:34:56+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-05T15:08:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-03T13:54:31+00:00","index":"","fulltext":""},{"type":"submitted","content":"Marine Biology","date":"2026-02-02T21:13:22+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"marine-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mabi","sideBox":"Learn more about [Marine Biology](https://www.springer.com/journal/227)","snPcode":"227","submissionUrl":"https://submission.nature.com/new-submission/227/3","title":"Marine Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"3c8d067c-f4ff-4511-adcd-983698be6323","owner":[],"postedDate":"February 10th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-10T15:52:05+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-10 15:52:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8769949","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8769949","identity":"rs-8769949","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}