Dynamics of foraging interactions between cookiecutter sharks (Isistius spp.) and short-finned pilot whales (Globicephala macrorhynchus) in Hawaiʻi

Dynamics of foraging interactions between cookiecutter sharks (Isistius spp.) and short-finned pilot whales (Globicephala macrorhynchus) in Hawaiʻi | 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 Dynamics of foraging interactions between cookiecutter sharks (Isistius spp.) and short-finned pilot whales (Globicephala macrorhynchus) in Hawaiʻi Natasha Walker-Milne, Yannis P. Papastamatiou, Sabre D. Mahaffy, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4808688/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Apr, 2025 Read the published version in Marine Biology → Version 1 posted 5 You are reading this latest preprint version Abstract Cookiecutter sharks ( Isistius spp. ) are small pelagic squaloid sharks found throughout tropical and sub-tropical waters that are known to feed opportunistically on a range of prey, including animals much larger than themselves. Short-finned pilot whales ( Globicephala macrorhynchus ) are resident to Hawaiʻi Island and are often observed with fresh and healed cookiecutter shark bites. In this study, cookiecutter bites were used to infer the spatiotemporal patterns of the foraging behaviour of sharks on pilot whales. Data were gathered off the Hawaiian Islands, within coordinates:(21°N, 158°W) to (18.5°N, 154.5°W). A photo-identification catalogue of 403 resident short-finned pilot whales (representing 5871 identifications of known individuals from 365 encounters from 2003–2012), were used to infer the prevalence and seasonal variation in shark presence. The mean proportion of the pilot whale’s body visible for documenting shark bites was 22.2% (SD ± 10.0). A total of 9293 fresh, healed, and scarred bite marks were documented on 396 of 403 whales (97.8%). Bites were most frequently documented on the head (33.1% of all bites), followed by the lateral sides (29.0%) and peduncle (27.2%), while the dorsal fin had the lowest percentage of bites (10.7%). The presence of fresh bites varied with day of the year, with peaks in April, July and mid-October and were also negatively correlated with sea surface temperature. There was also a peak in fresh bites in the transition between crescent and quarter lunar phases. These results provide further evidence that cookiecutter sharks in Hawaiʻi may perform seasonal migrations or dietary shifts. Cookiecutter foraging Hawaiʻi pilot whale shark Figures Figure 1 Figure 2 Figure 3 Introduction Understanding the behaviour, distribution and movement patterns of mesopelagic predators can be a challenging undertaking. This can be especially difficult for smaller predators such as sharks from the genus Isistius . Deemed cookiecutter sharks due to their distinctive feeding behaviour, cookiecutter sharks are small cigar shaped, pelagic squaloid sharks typically no more than 50 cm in length with a short snout and large eyes (Jahn and Haedrich 1988 ). Within the genus there are at least two species, the smalltooth cookiecutter ( I. brasiliensis ) and the largetooth cookiecutter ( I. plutodus ), with the largetooth distinguished via variation in colouration and fin shape (Garrick and Springer 1964 ; de Figueiredo Petean and R. de Carvalho 2018). Both share similar distributions being found in tropical waters typically from around 20 o N to 20 o S and depths down to 3500 m (Strasburg 1963 ; Jones 1971 ; Jahn and Haedrich 1988 ; Nakano and Tabuchi 1990 ), however I. plutodus has only been identified from sporadic identifications, mainly in the Atlantic Ocean (Garrick and Springer 1964 ; de Figueiredo Petean and R. de Carvalho 2018). Cookiecutter sharks have an unusual feeding mode that facilitates the removal of a “plug” of flesh from their prey, leaving a characteristic crater wound on the animal if the attack was successful and a crescent shaped wound if the full plug of flesh has not been removed (Jones 1971 ; Papastamatiou et al. 2010 ). Cookiecutter shark prey consists of the majority of large open ocean predators including marine mammals, teleosts, sharks, and large game fish (Papastamatiou et al. 2010 ; Hoyos-Padilla et al. 2013 ; Best and Photopoulou 2016 ; Santos et al. 2024 ). Wounds from cookiecutter sharks have been described on many cetacean species, both odontocetes and mysticetes, with the exception of those which are resident to polar regions (LeBoeuf 1987 ; Bornatowski et al. 2012 ; Best and Photopoulou 2016 ; Grace et al. 2018 ). In Hawaiʻi, cookiecutter bites have been observed on a number of species, both resident and open-ocean, including spinner dolphins ( Stenella longirostris ) (Norris and Dohl 1990 ), goose-beaked ( Ziphius cavirostris ) and Blainville’s ( Mesoplodon densirostris ) beaked whales (McSweeney et al. 2007 ), and Hawaiian monk seals ( Neomonachus schauinslandi ) (Hiruki et al. 1993 ). Due to the limited known distribution of I. plutodus we presume all bites on Hawaiian cetaceans are from I. brasiliensis. Despite their ability to feed on prey much larger than themselves, stomach contents and chemical tracer analysis reveal that the majority of the cookiecutters’ diet in the central Pacific around Hawaiʻi still consist of smaller micronekton prey such as squid (Carlisle et al. 2021 ). Based on catch data and stable isotopes, it is thought that cookiecutter sharks are diel vertical migrators remaining in deeper water during the day and swimming to the surface at night (Jahn and Haedrich 1988 ; Nakano and Tabuchi 1990 ; Papastamatiou et al. 2010 ). These studies have also provided evidence that cookiecutter sharks are present in Hawaiian waters year-round, but may display seasonal migrations or shifts in diet, being more abundant during the summer and fall months (Papastamatiou et al. 2010 ; Carlisle et al. 2021 ). Short-finned pilot whales ( Globicephala macrorhynchus ), hereafter referred to as pilot whales, are the most frequently encountered cetacean species in and around the main Hawaiian Islands (Baird et al. 2013 ; Baird et al. 2024 ). An abundance estimate in 2017 for the Exclusive Economic Zone (EEZ) surrounding the Hawaiian archipelago was approximately 8,000 individuals (Bradford et al. 2021 ), however this estimate does not distinguish between insular or island-associated and pelagic populations (Baird 2016 ). Data from extensive satellite tagging and association analyses based on photo-identification has shown that the pilot whale population around the main Hawaiian Islands is divided into three insular communities showing a propensity for slope areas with depths less than 3000 m (Mahaffy et al. 2015 ; Baird 2016 ; Van Cise et al. 2017 ; Kratofil et al. 2023 ). A long-term photo-identification study focused on the eastern community demonstrated that pilot whales off the island of Hawaiʻi have a hierarchical social structure where individuals travel in stable, mixed-sex social units composed of related individuals and that multiple units preferentially associate to form social clusters (Mahaffy et al. 2015 , Van Cise et al. 2017 ). Some pilot whale groups show year-round residency to the area while others termed “visitors” only used the area occasionally (Mahaffy et al. 2015 ). Dive behaviour from depth-transmitting satellite tags in Hawaiʻi revealed that pilot whales dive deepest during the day (31% of dives; mean = 666.1 ± 16.7 m) but more frequently at night (58% of dives, mean = 415.5 ± 14.8 m), possibly following vertical prey migrations of Histioteuthid and Onychoteuthid squid (Young 1975 ; Owen et al. 2019 ). Lunar phase also influenced dive behaviour, with animals diving deeper, longer, and farther from shore during a full moon compared to a new moon (Owen et al. 2019 ). Dives during the winter months (February – April) were also deeper, longer, and further from shore than in autumn or summer (Owen et al. 2019 ). When studying cryptic and difficult to observe species, the use of a proxy can be employed to gather data. For example, many specimens of giant squid ( Architeuthis spp .) are recovered from sperm whale ( Physeter macrocephalus ) stomach contents (Clarke 1966 ; Clarke and Roper 1998 ; Santos et al. 2002 ). In this study, the cookiecutter shark bite wounds and scars observed on another species are used as a proxy to provide unique insights into the foraging dynamics of the sharks. Here we use cookiecutter shark bites on pilot whales to assess changes in shark foraging ecology. As our study population of pilot whales are largely resident to Hawaiʻi Island, they remove confounding factors from previous studies using landed pelagic fish as a proxy (e.g. where location of capture is unknown, Papastamatiou et al. 2010 ). Since previous studies have suggested seasonal movements of cookiecutter sharks in Hawaiian waters (Papastamatiou et al. 2010 ), we predict that the probability of pilot whales being bitten will be highest in the summer. Furthermore, as noted, pilot whale space use and diving behaviour varies with lunar phase (Owen et al. 2019 ). During the full moon, pilot whales are farther offshore and diving deeper, thus we would expect more overlap with cookiecutter sharks during full moons versus the new moon. Materials and Methods Study location and photographic data The study was conducted off the leeward (western) side of Hawaiʻi Island over an area of approximately 2500 km 2 , with depths ranging from shallow coastal water to approximately 5000 m. Pilot whale photos were collected from 2003–2012 as part of a long-term, multi-species assessment of cetaceans in Hawaiʻi (see Baird et al. 2013 ) as well as from opportunistic sightings by the Wild Whale Research Foundation. During directed research surveys, groups were approached for species confirmation, to take photos for individual identification and to collect sighting data, including date, GPS location (lat / long), and group size (min, max, best) (see Baird et al. 2013 ). Attempts were made to photograph the right and left sides of every individual in the group regardless of size or distinctiveness level, although this was not always possible due to field limitations such as time of day, Beaufort sea conditions and fuel constraints. A sighting or group was defined using a 1000 m chain-rule where all individuals within 1000 m of other individuals are assumed to be associated (Mahaffy et al. 2015 ). Methodology used to process photos for photo-identification is discussed in detail in Mahaffy et al. ( 2015 ). Briefly, photos from each sighting were sorted by individual using unique natural markings on the dorsal fin and were then visually compared to the photo identification catalogue; if a match was found, the individual was added to the catalogue under the existing identification (ID) number (e.g., HIGm####) and if no match was found the individual was assigned a new ID. The best photo from each sighting of an individual was assigned a photo quality rating (1 = poor, 2 = fair, 3 = good, 4 = excellent) and the individual was also rated for distinctiveness (1 = not distinctive, 2 = slightly distinctive, 3 = distinctive, 4 = very distinctive) when it was added to the catalogue (Mahaffy et al. 2015 ). Analyses were restricted to distinctive or very distinctive individuals with good or excellent quality photos. Individual sighting histories in the photo-identification catalogue were used to determine the degree of residency to the island of Hawaiʻi; only pilot whale individuals resident to the island (those recorded in five or more sightings over four or more years (Mahaffy et al. 2015 )) were included in the study. Cookiecutter shark bite analysis Within each sighting of an individual, all relevant photos were used, allowing for the assessment of a larger proportion of the body than visible in a single photograph. Photos were examined to determine cookiecutter shark bite presence, number, and location on the body (Fig. 1 ). The body was divided into head, mid lateral, dorsal fin, and peduncle sections and further into 10 sections, five of which were below the water line (Fig. 1 ). For each sighting of an individual, we recorded which of the five sections above the waterline were visible for each side, to determine the proportion of the body that was available for analysis. Cookiecutter shark bites were distinguished from similarly sized wounds and scars (such as those caused by conspecifics) by their slightly ovoid shape and uniform depth (Fig. 2 ) and their status were classified as fresh, healing or scarred. Fresh bites were those that were pink or red in colour and/or those which displayed an early immune response such as swelling or “foaming” (Fig. 2 a, b). All bites that were classified as fresh were yet to be colonised by cyamids (whale lice, Isocyamus delphini) , and are suspected to be less than one week old as cyamid colonisation was often observed within approximately one week of the bite occurring (Mahaffy, unpubl data ). Healing bites were crater-shaped depressions in the issue typically orange in colour due to the presence of cyamids (Fig. 2 b, c). Healing occurs in a number of stages that may range from 4 to ≥ 95 days in duration (Gimenez et al. 2011 ). Once bites have healed to the point of scarring, the removed flesh is typically replaced with healed, re-pigmented tissue that may have a slightly lighter-coloured halo around the original wound and an uneven appearance around the border (Fig. 2 ) (Balbuena and Raga 1991 ; Gimenez et al. 2011 ). At this stage of healing, cyamids are absent as conditions for attachment become unsuitable and they typically move back to their usual areas around the mouth and other crevasses in the skin (Balbuena and Raga 1991 ). Scar shapes were similar to those observed by Dwyer and Visser ( 2011 ), typically forming a round or ovoid convex shape (Fig. 2 ). Observed scars that had healed in a crescent shape were likely the result of an unsuccessful cookiecutter attack which did not result in the full removal of the typical plug of flesh. Statistical analysis and modelling To explain spatiotemporal patterns in the presence and absence of bite marks, a combination of abiotic data (date, year, sea surface temperature (SST), lunar phase, lunar illumination (LI)) and data on social clusters were included in the statistical analysis. Weekly average sea surface temperatures were obtained from National Oceanic and Atmospheric Administration (NOAA) using AVHRR Pathfinder Sea-Surface Temperature v5 and v5.1 for the study area (Supplementary Fig S1). The area used for SST was from 19 o N to 20.25 o N and from 156 o W to 158 o W. Lunar phase and lunar illumination were obtained using the lunar package in R (Lazaridis 2015 ), for each survey date. Phases were combined into five groups combining similar illumination: waxing crescent and waning crescent were combined, as were waxing gibbous and waning gibbous, as per Owen et al. ( 2019 ). Seasons were grouped into autumn (November to January), Winter (February to April), Spring (May to July), and Summer (August to October) as per Flament et al. ( 1996 ). As individuals within the same social cluster are likely to experience similar exposure to cookiecutter sharks, social cluster (from Mahaffy et al. ( 2015 )) was included in subsequent analyses. In order to investigate the distribution of fresh bites across a pilot whale’s body, a comparison of the observed versus expected number of bites was conducted based on the proportion of the body area seen (Fig. 1 ). Fresh bite proportions for each location were calculated and adjusted for whether one or both sides of the body were seen. A chi-squared test was performed using R to compare observed and expected, assessing deviations from the expected distribution based on the body area seen. Presence or absence of fresh bites for each animal in each sighting were modelled in R Statistical Software (v4.2.2; R Core Team 2022 ) using generalised additive binomial mixed models (GAMM) with a complementary log-log link due to zero inflated data. GAMMs were applied using Gamm4 (Wood and Scheipl 2020 ). Modelling was undertaken with temperature, lunar phase, lunar illumination, and Julian date being used as explanatory variables, with pilot whale social cluster included as a random effect to account for potential grouping of data. A likelihood ratio test was conducted to assess effectiveness of the inclusion of the random effect, and Spearman’s rank correlations were used to test for collinearity. The best fitting model was selected using a forward stepwise model selection (Zuur et al. 2009 ), based on Akaike information criterion (AIC) scores of the underlying generalised linear model of the GAMM (Supplemental Table 1). The percentage of the pilot whale visible had an exponential relationship with the percentage of animals observed with fresh bites, therefore this was added to the model as an offset. Model accuracy was tested using K-fold cross validation using the caret package in R (Kuhn 2021 ). Results Photos from 403 individual pilot whales from 16 social clusters were examined. Photos were obtained from a total of 5871 identifications (i.e., repeated encounters of individuals). Identifications were distributed roughly similarly across lunar phases (ranging from 282 to 382 identifications). There were similar numbers of identifications available from the Hawaiian winter (348), spring (383), and summer (321), but fewer (207) available from the Hawaiian autumn. Bites of various stages were observed on 396 of the 403 individuals (98.3%). A total of 169 fresh bites were recorded on 115 individuals, representing 161 identifications. Of the 115 individuals with fresh bites, most (108) had only a single fresh bite, six had two fresh bites, and one had three fresh bites. There were 575 healing bites recorded on 211 individuals, representing 490 identifications, while 8549 scars were recorded on 389 individuals, representing 2779 identifications. There were occurrences of whales having more than one healing bite, but it could not be determined if the bites occurred relatively close in time (e.g., during the same day or week). Many individuals had multiple bites in varying states of healing/re-pigmentation. The mean proportion of the body seen during each sighting was 22.2% (SD ± 10.0), therefore more bites were likely present but unobservable due to being below the waterline. Most fresh bites recorded were located on the head (33.1%), lateral sides of the body (29%) and peduncle area (26.6%) while the dorsal fin had the lowest percentage of fresh bites (just over 10%) (Table 1 ). Table 1 Location of fresh cookiecutter shark bites on short-finned pilot whales. Comparisons of observed versus expected fresh bites by location. % of bites by location n Observed n Expected Dorsal Fin 10.7 18 16 Head 33.1 53 33 Lateral 29.0 48 48 Peduncle 27.2 42 64 Pearson’s Chi-sq = 9.3348, df = 3, p value = 0.02515 When taking the area of each section of the body into account and whether one or both sides were photographed during a sighting, there was a greater than expected number of bites on the head ( X 2 = 9.33, P = 0.025) (Table 1 ), and a lower than expected number of bites on the peduncle. Healing bites and scars were observed in every month of the year, and fresh bites were observed in all months except September (Table 2 ). Table 2 – Breakdown of total cookiecutter bites on short-finned pilot whales by status of bite and month of year Month Total Individuals Total Identifications Total Fresh bites Total Healing Bites Total Scarred bites January 122 185 4 8 87 February 48 48 1 2 37 March 155 233 8 32 160 April 315 1340 39 139 1815 May 263 589 17 88 1285 June 35 35 2 2 21 July 356 1117 26 102 1732 August 284 622 17 73 1248 September 125 247 0 20 204 October 156 379 23 22 551 November 127 523 17 40 675 December 157 553 16 47 734 Total 2143 5871 170 575 8549 The GAMM showed that the predicted binomial presence/absence was influenced by surface temperatures, Julian day of the year and lunar illumination as smooth terms, including an offset of the percentage of the body viewed in each sighting plus the social cluster of the animal in question as a random effect (Table 3 ). There was a decreased likelihood of fresh bites at higher temperatures (Fig. 3 a). Day of the year also influenced the likelihood of fresh bites with three distinct peaks centred around the 115th, 200th and 290th days of the year approximately corresponding to late April, mid-July, and mid-October (Fig. 3 b). The first peak in bite probability at day 111 was the lowest peak with whales showing a probability of fresh bite occurrence of 0.04 (SE ± 0.008). The second peak at day 201 was 0.05 (SE ± 0.009), and the third peak of 0.06 (SE ± 0.01) occurred on day 284. Lunar illumination also showed a significant influence with increases in the probability of fresh bites during the transition between crescent moon and quarter (Fig. 3 c). Year was also tested as a random effect, but the value was too close to zero to be effective as a random effect. Table 3 Results of model of best fit for effects of abiotic variables on the prevalence of fresh cookiecutter bites on short-finned pilot whales. Coefficients and diagnostics (Chi-sq and P-values) indicate the effect of each parameter level. X 2 df p-value RMSE : 1.75 Parametric Response Variable SD : 0.09 Sea surface temperature 35.92 1 < 0.0001 Non-parametric Response Lunar illumination 141.8 8.816 < 0.0001 Julian Date 313.9 8.530 < 0.0001 The inclusion of pilot whale social cluster in the model significantly improved model accuracy ( Χ ²= 853.07, p < 0.0001), indicating the presence of cluster-specific effects. However, the variance component for the random effect (cluster) was estimated to be 0.355 (SD ± 0.59), indicating high variability among clusters in the latent scale of the complementary log-log model. The intraclass correlation coefficient (ICC) was approximately 0.097, suggesting that around 9.7% of the variability in the presence or absence of fresh bites could be attributed to differences between clusters. Discussion Our results show that probability of cookiecutter bites on resident pilot whales varies by season, lunar phase, and water temperature. In this study we obtain additional understanding of cookiecutter shark foraging ecology (and their interaction with a marine mammal prey species) by using bite wounds on free-swimming pilot whales. Unlike previous studies, which relied on dead pelagic fish brought to port, by observing free-swimming pilot whales we know the approximate geographic area where bites took place (Papastamatiou et al. 2010 ). We estimate that fresh bites observed on pilot whales likely occurred within one week of the individual being photographed, and therefore interactions almost certainly took place waters off the west side of Hawaiʻi Island. By concentrating on a resident cetacean population, we could determine how the probability of fresh bites varied based on both abiotic conditions and season. Stable isotopes analyses of the livers and muscles tissues of cookiecutter sharks suggest that cookiecutter sharks exhibit seasonal shifts in diet, or in the location where they forage (Carlisle et al. 2021 ). We observed a general seasonal occurrence in fresh bites. While there was an overall increase in bite probability in April, the number of bites were not consistent, showing zero fresh bites in September and lower numbers of bites in May and August (Table 2 ). Cookiecutter shark bite probability peaked in October (Julian day 290) but was lowest during the winter months (Table 2 , Fig. 3 a). There were troughs between the peaks where virtually no pilot whales were observed. Why these reductions in pilot whale sightings occurred is unclear, but it was impossible to measure bite probability during these periods. The probability of fresh cookiecutter bites on bigeye tuna ( Thunnus obesus ), the majority of which were caught within the Hawaiʻi EEZ, similarly peaks from October-December (Papastamatiou et al. 2010 ). Swordfish ( Xiphias gladius ) are primarily caught outside the Hawaiian EEZ and show a peak in fresh bites from March-May (Papastamatiou et al. 2010 ). Combined these results suggest either that cookiecutter sharks show seasonal shifts in their diet or display seasonal migrations moving away from the main Hawaiian Islands in the winter and returning in the late spring. The diet of cookiecutter sharks in Hawaiʻi includes squid (Papastamatiou et al. 2010 ; Carlisle et al. 2021 ), which is also prey for pilot whales, suggesting the potential for competitive interactions between sharks and pilot whales (Seagars and Henderson 1985 ; Sinclair 1992 ). A high biomass of vertical diel migrating micronekton, including squid, occurs off the west coast of Hawaiʻi Island, and the distance from shore also changes in relation to day and lunar phase (Benoit-Bird et al. 2001 ). Pilot whales in Hawaiʻi dive deeper during the day (mean = 666 m) than at night (mean = 415 m), although they perform more dives at night, and this variation may increase the rate at which pilot whales are encountering cookiecutter sharks as they move into shallower waters at night following the vertical diel migrating micronekton. Our data shows an increase in shark bite probability peaking in the transition from crescent to quarter moon (Fig. 3 ); this may either be a product of overlapping use of the vertical water column, or, as pilot whales in Hawaiʻi have been observed to move farther offshore as lunar illumination increases, an indication of movement into an area occupied by more cookiecutter sharks (Owen et al. 2019 ). Pilot whale social structure may influence the dynamics of interaction between the two study species, and model predictions had a high standard deviation, suggesting that there is substantial variation in the effect across social cluster. Pilot whales in Hawaiʻi are known to have a social structures characterized by strong, long-term associations, suggesting individuals from the same social groups are exposed to cookiecutter sharks at similar rates and should may therefore have similar numbers of bites (Alves et al. 2013 ; Mahaffy et al. 2015 ). This may suggest cookiecutter sharks show heterogeneity in their distribution and that pilot whales within a group are more likely to get bitten when they move through a high-density cookiecutter shark area. Sea surface temperature showed a significant effect on the probability of pilot whales being bitten, with bite probability decreasing as SSTs increased. Based on trawl data from the north Pacific, cookiecutter sharks were caught at temperatures ranging from 18 o C to 26 o C (Nakano and Tabuchi 1990 ). We recorded no fresh bites on pilot whales in September, the month with the highest average temperatures (27 ± 0.35 o C), despite 125 individuals being photographed from nine different sightings. Water temperatures off Hawaiʻi are relatively stable but these results further suggest that cookiecutter sharks may avoid surface waters > 26–27ºC, although this assumes that sharks are biting pilot whales at the surface. The probability of fresh bites also changes with lunar illumination, with a peak occurring between crescent and gibbous moon phases (Fig. 3 c). The increases in bite prevalence on pilot whales during these times may be attributed to changes in the lunar movement of micronekton or the pilot whales themselves. Micronekton in the mesopelagic boundary community increase their depth and move farther offshore during periods of high lunar illumination (Benoit-Bird et al. 2009 ; Abecassis et al. 2015 ; Prihartato et al. 2016 ; Comfort et al. 2017 ). Increased surface illumination may also impact cookiecutter shark ability to hunt in surface waters or attract prey (Widder 1998 ). Finally, pilot whales dive shallower and for shorter durations during the Quarter and Crescent lunar phases, which may cause them to spend more time in the near-surface waters where they may be more susceptible to cookiecutter shark bites (Owen et al. 2019 ). We would predict that bites are more likely to occur at the surface due to the amount of time cookiecutter sharks and pilot whales spend there relative to deeper depths (as pilot whales are only diving below the surface for relatively short periods of time). Cookiecutter sharks appear to show some selection for biting the head and dorsal areas of pilot whales, while avoiding or randomly biting the lateral and peduncle areas. However, in studies involving both odontocetes and mysticetes there were higher numbers of cookiecutter bites on the peduncle of mysticetes in comparison to odontocetes (Best and Photopoulou 2016 ). In other species, such as rough-toothed dolphins ( Steno bredanensis ), examination of the ventral side was facilitated through their aerial behaviour and this area was often covered in cookiecutter scars (Baird 2016 ). Unfortunately, pilot whales rarely leap out of the water and examination of the ventral side was therefore not possible, although some records of underwater sightings were obtained. Hence, our estimates of bite probabilities on short-finned pilot whales are conservative. We provide new insight into the foraging dynamics of cookiecutter sharks, an incredibly versatile pelagic predator whose bites are ubiquitous on pelagic predators in tropical waters. By using bites on free-swimming pilot whales, we can approximate the geographic location where bites occurred, unlike previous studies with pelagic fishes which could only approximate bite location to the Hawaiian Islands (Papastamatiou et al. 2010 ). While cookiecutter shark bites on pilot whales may not be fatal (although some small dolphins may die from bites that penetrate into the abdominal cavity, Baird 2016 ), they may still reduce pilot whale fitness. Due to their potential high abundance, and ability to play an important ecological and economic role (e.g., cookiecutter shark bites reduce the price of market fish at auction, Papastamatiou et al. 2010 ), additional studies of cookiecutter shark foraging dynamics are warranted. Declarations Compliance with Ethical Standards The authors declare no conflict of interest. Data were collected under NOAA Fisheries Scientific Research Permits 731-1509, 731-1774, and 15330 issued to RWB, and research methodologies were approved by the Cascadia Research Collective Institutional Animal Care and Use Committee. Acknowledgments Funding for field work during which photos were obtained was provided by the Wild Whale Research Foundation, Cascadia Research Collective, Southwest Fisheries Science Center (SWFSC), Pacific Islands Fisheries Science Center, and Chief of Naval Operations/Environmental Readiness Division. The authors would like to thank D. Bailey, A. MacGregor, S. Elliott, and J. Clarke from the University of Glasgow for all their help and support. All the staff at Cascadia Research Collective, Olympia, Washington including but not limited to A. Allen, A. Douglas, N, Harrison, J. Welsh and the rest of the whole team whose help and advice was immeasurable. Data Availbility Statement The datasets generated during and/or analysed during the current study are available in the Zenodo repository, [https://doi.org/10.5281/zenodo.12733235]. The code used for analysis is available on GitHub, [https://github.com/NWMilne/Cookiecutters/tree/v1.0.1]. These resources are accessible and comply with the repository's data policies. Funding for field work during which photos were obtained was provided by the Wild Whale Research Foundation, Cascadia Research Collective, Southwest Fisheries Science Center (SWFSC), Pacific Islands Fisheries Science Center, and Chief of Naval Operations/Environmental Readiness Division. The authors would like to thank D. Bailey, A. MacGregor, S. Elliott, and J. Clarke from the University of Glasgow for all their help and support. All the staff at Cascadia Research Collective, Olympia, Washington including but not limited to A. Allen, A. Douglas, N, Harrison, J. Welsh and the rest of the whole team whose help and advice was immeasurable. References Abecassis M, Polovina J, Baird RW, Copeland A, Drazen JC, Domokos R, Oleson E, Jia Y, Schorr GS, Webster DL, Andrews RD (2015) Characterizing a foraging hotspot for short-finned pilot whales and Blainville's beaked whales located off the west side of Hawaiʻi Island by using tagging and oceanographic data. PLoS ONE 10. https://doi.org/10.1371/journal.pone.0142628 Alves F, Quérouil S, Dinis A, Nicolau C, Ribeiro C, Freitas L, Kaufmann M, Fortuna C (2013) Population structure of short-finned pilot whales in the oceanic archipelago of Madeira based on photo-identification and genetic analyses: implications for conservation. Aquat Conserv Mar Freshw Ecosyst 23:758–776. https://doi.org/10.1002/aqc.2332 Baird RW (2016) The lives on Hawaiʻi's dolphins and whales: natural history and conservation. 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Can J Zool 69:141–145. https://doi.org/10.1139/z91-021 Benoit-Bird KJ, Au WW, Wisdom DW (2009) Nocturnal light and lunar cycle effects on diel migration of micronekton. Limnol Oceanogr 54:1789–1800. https://doi.org/10.4319/lo.2009.54.5.1789 Benoit-Bird KJ, Au WWL, Brainard RE, Lammers MO (2001) Diel horizontal migration of the Hawaiian mesopelagic boundary community observed acoustically. Mar Ecol Prog Ser 217:1–14. https://doi.org/10.3354/meps217001 Best PB, Photopoulou T (2016) Identifying the demon whale-biter: patterns of scarring on large whales attributed to a cookie-cutter shark Isistius sp . PLoS ONE 11. https://doi.org/10.1371/journal.pone.0152643 Bornatowski H, Wedekin LL, Heithaus MR, Marcondes MCC, Rossi-Santos MR (2012) Shark scavenging and predation on cetaceans at Abrolhos Bank, eastern Brazil. J Mar Biol Assoc UK 92:1767–1772. https://doi.org/10.1017/S0025315412001154 Bradford A, Oleson EM, Forney KA, Moore JE, Barlow J (2021) Line-transect abundance estimates of cetaceans in U.S. waters around the Hawaiian Islands in 2002, 2010, and 2017. NOAA Tech Memo Carlisle AB, Allan EA, Kim SL, Meyer L, Port J, Scherrer S, O'Sullivan J (2021) Integrating multiple chemical tracers to elucidate the diet and habitat of cookiecutter sharks. Sci Rep 11:11809. https://doi.org/10.1038/s41598-021-89903-z Clarke MR (1966) Cephalopods as prey. III. Cetaceans. Philos Trans R Soc Lond B Biol Sci 351:1053–1065. https://doi.org/10.1098/rstb.1996.0093 Clarke MR, Roper CFE (1998) Cephalopods represented by beaks in the stomach of a sperm whale stranded at Paekakariki, North Island, New Zealand. Afr J Mar Sci 20:129–133. https://doi.org/10.2989/025776198784126601 Comfort CM, Smith KA, McManus MA, Neuheimer AB, Sevadjian JC, Ostrander CE (2017) Observations of the Hawaiian mesopelagic boundary community in daytime and nighttime habitats using estimated backscatter. AIMS Geosci 3:304–326. https://doi.org/10.3934/geosci.2017.3.304 de Figueiredo Petean F, de Carvalho MR (2018) Comparative morphology and systematics of the cookiecutter sharks, genus Isistius Gill (1864) (Chondrichthyes: Squaliformes: Dalatiidae ). PLoS ONE 13. https://doi.org/10.1371/journal.pone.0201913 Dwyer S, Visser I (2011) Cookie cutter shark (Isistius sp.) bites on cetaceans, with particular reference to killer whales (Orcinus orca). Aquat Mamm 37:111–138. https://doi.org/10.1578/AM.37.2.2011.111 Flament P, Kennan S, Lumpkin R, Sawyer M, Stroup E (1996) Ocean atlas of Hawaiʻi. Department of Oceanography, School of Ocean and Earth Science and Technology (SOEST). University of Hawaiʻi at Mānoa, Hawaiʻi Garrick JAF, Springer S (1964) Isistius plutodus , a new squaloid shark from the Gulf of Mexico. Copeia 1964:678–682. https://doi.org/10.2307/1441443 Gimenez J, De Stephanis R, Gauffier P, Esteban R, Verborgh P (2011) Biopsy wound healing in long-finned pilot whales ( Globicephala melas ). Vet Rec 168:101b. https://doi.org/10.1136/vr.c5284 Grace MA, Dias LA, Maze-Foley K, Sinclair C, Mullin KD, Garrison L, Noble L (2018) Cookiecutter shark bite wounds on cetaceans of the Gulf of Mexico. Aquat Mamm 43:491–499. https://doi.org/10.1578/AM.44.5.2018.491 Hiruki LM, Gilmartin WG, Becker BL, Stirling I (1993) Wounding in Hawaiian monk seals ( Monachus schauinslandi ). Can J Zool 71:458–468. https://doi.org/10.1139/z93-066 Hoyos-Padilla M, Papastamatiou YP, O'Sullivan J, Lowe CG (2013) Observation of an attack by a cookiecutter shark ( Isistius brasiliensis ) on a white shark ( Carcharodon carcharias ). Pac Sci 67:129–134. https://doi.org/10.2984/67.1.10 Jahn AE, Haedrich RL (1988) Notes on the pelagic squaloid shark Isistius brasiliensis . Biol Oceanogr 5:297–309. https://doi.org/10.1080/01965581.1987.10749519 Jones EC (1971) Isistius brasiliensis , a squalid shark, the probable cause of wounds on fishes and cetaceans. Fish Bull 69:791–798 Kratofil MA, Harnish AE, Mahaffy SD, Henderson EE, Bradford AL, Martin SW, Lagerquist BA, Palacios DM, Oleson EM, Baird RW (2023) Biologically important areas II for cetaceans within U.S. and adjacent waters – Hawaiʻi Region. Front Mar Sci 10. https://doi.org/10.3389/fmars.2023.1053581 Kuhn M (2021) Building predictive models in R using the caret package: classification and regression training. J Stat Softw 28:1–26. https://doi.org/10.18637/jss.v028.i05 Lazaridis E (2015) lunar: lunar phase & distance, seasons and other environmental factors. http://statistics.lazaridis.eu LeBoeuf BJ (1987) Crater wounds on northern elephant seals: the cookiecutter shark strikes again. Fish Bull 85:387–392 Mahaffy SD, Baird RW, McSweeney DJ, Webster DL, Schorr GS (2015) High site fidelity, strong associations, and long-term bonds: short-finned pilot whales off the island of Hawai‘i. Mar Mamm Sci 31:1427–1451. https://doi.org/10.1111/mms.12234 McSweeney DJ, Baird RW, Mahaffy SD (2007) Site fidelity, associations, and movements of Cuvier's ( Ziphius cavirostris ) and Blainville's ( Mesoplodon densirostris ) beaked whales off the island of Hawaiʻi. Mar Mamm Sci 23:666–687. https://doi.org/10.1111/j.1748-7692.2007.00135.x Nakano H, Tabuchi M (1990) Occurrence of the cookiecutter shark Isistius brasiliensis in surface waters of the North Pacific Ocean. Jpn J Ichthyol 37:60–63. https://doi.org/10.11369/jji1950.37.60 Norris KS, Dohl TP (1990) Behaviour of the Hawaiian spinner dolphin, Stenella longirostris . Fish Bull 77:821–850 Owen K, Andrews RD, Baird RW, Schorr GS, Webster DL (2019) Lunar cycles influence the diving behavior and habitat use of short-finned pilot whales around the main Hawaiian Islands. Mar Ecol Prog Ser 629:193–206. https://doi.org/10.3354/meps13123 Papastamatiou YP, Wetherbee BM, O’Sullivan J, Goodmanlowe GD, Lowe CG (2010) Foraging ecology of cookiecutter sharks ( Isistius brasiliensis ) on pelagic fishes in Hawaii, inferred from prey bite wounds. Environ Biol Fishes 88:361–368. https://doi.org/10.1007/s10641-010-9649-2 Prihartato PK, Irigoien X, Genton MG, Kaartvedt S (2016) Global effects of moon phase on nocturnal acoustic scattering layers. Mar Ecol Prog Ser 544:65–75. https://doi.org/10.3354/meps11612 R Core Team (2022) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/ Santos MB, Pierce GJ, Hartmann MG, Smeenk C, Addink MJ, Kuiken T, Reid RJ, Patterson IAP, Lordan C, Rogan E, Mente E (2002) Additional notes on stomach contents of sperm whales Physeter macrocephalus stranded in the north-east Atlantic. J Mar Biol Assoc UK 82:501–507. https://doi.org/10.1017/s0025315402005787 Santos L, Veloso JV, Santos TB, Bezerra NP, Oliveira P, Hazin FH (2024) An equatorial mid-Atlantic Ocean archipelago as nursery area for the cookiecutter shark: Investigating foraging strategies of neonates through bite mark inferences. J Fish Biol. https://doi.org/10.1111/jfb.15664 Seagars DJ, Henderson JR (1985) Cephalopod remains from the stomach of a short-finned pilot whale collected near Santa Catalina Island, California. J Mammal 66:777–779. https://doi.org/10.2307/1380806 Sinclair EH (1992) Stomach contents of short-finned pilot whales ( Globicephala macrorhynchus ) from the southern California bight. Mar Mamm Sci 8:76–81. https://doi.org/10.1111/j.1748-7692.1992.tb00127.x Strasburg DW (1963) The diet and dentition of Isistius brasiliensis , with remarks on tooth replacement in other sharks. Copeia 1963:33–40. https://doi.org/10.2307/1441272 Van Cise AM, Martien KK, Mahaffy SD, Baird RW, Webster DL, Fowler JH, Oleson EM, Morin PA (2017) Familial social structure and socially driven genetic differentiation in Hawaiian short-finned pilot whales. Mol Ecol 26:6730–6741. https://doi.org/10.1111/mec.14397 Widder E (1998) A predatory use of counterillumination by the squaloid shark, Isistius brasiliensis . Environ Biol Fishes 53:267–273. https://doi.org/10.1023/A:1007498915860 Wood S, Scheipl F (2020) gamm4: generalized additive mixed models using 'mgcv' and 'lme4'. R package version 0.2-6 Young RE (1975) Transitory eye shapes and the vertical distribution of two midwater squids. Pac Sci 29:243–255 Zuur AF, Ieno EN, Walker NJ, Savelieve AA, Smith GM (2009) Mixed effects models and extensions in ecology with R. Springer, New York, pp 323–341 Supplementary Files SupplementaryInformation.docx Cite Share Download PDF Status: Published Journal Publication published 01 Apr, 2025 Read the published version in Marine Biology → Version 1 posted Editorial decision: Revise and Resubmit 06 Sep, 2024 Reviewers agreed at journal 13 Aug, 2024 Reviewers invited by journal 02 Aug, 2024 Editor assigned by journal 30 Jul, 2024 First submitted to journal 26 Jul, 2024 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. 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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-4808688","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":335394804,"identity":"15e7496a-fad2-44ba-968d-7a4159f31d5f","order_by":0,"name":"Natasha Walker-Milne","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-9575-0626","institution":"University of Glasgow College of Medical Veterinary and Life Sciences","correspondingAuthor":true,"prefix":"","firstName":"Natasha","middleName":"","lastName":"Walker-Milne","suffix":""},{"id":335394805,"identity":"1b58ca7c-22b4-48f2-88eb-f5383a08ba1a","order_by":1,"name":"Yannis P. Papastamatiou","email":"","orcid":"","institution":"Florida International University","correspondingAuthor":false,"prefix":"","firstName":"Yannis","middleName":"P.","lastName":"Papastamatiou","suffix":""},{"id":335394806,"identity":"6bb6e9ae-9030-4f72-a25f-5d820d346070","order_by":2,"name":"Sabre D. Mahaffy","email":"","orcid":"","institution":"Cascadia Research Collective","correspondingAuthor":false,"prefix":"","firstName":"Sabre","middleName":"D.","lastName":"Mahaffy","suffix":""},{"id":335394807,"identity":"76590ff8-d33b-47e0-b313-6d16c10857cf","order_by":3,"name":"Robin W. Baird","email":"","orcid":"","institution":"Cascadia Research Collective","correspondingAuthor":false,"prefix":"","firstName":"Robin","middleName":"W.","lastName":"Baird","suffix":""}],"badges":[],"createdAt":"2024-07-26 14:17:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4808688/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4808688/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00227-025-04633-4","type":"published","date":"2025-04-01T15:57:05+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":63544797,"identity":"133a237a-c1ae-42eb-a2b2-66a49113cd2e","added_by":"auto","created_at":"2024-08-29 11:08:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":232745,"visible":true,"origin":"","legend":"\u003cp\u003eAreas on short-finned pilot whale body where cookiecutter shark bites were recorded. A) Location on body B) Division of body used to approximate percentage sections of the pilot whale’s body that was observed during each sighting. The maximum total body observed could only be 50% as the ventral side was below the waterline.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4808688/v1/b5e16c7353951f8ef47f2ec1.png"},{"id":63544804,"identity":"68556059-48f8-4bd2-8ac7-6c069b32017c","added_by":"auto","created_at":"2024-08-29 11:08:15","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":672144,"visible":true,"origin":"","legend":"\u003cp\u003eExamples of cookiecutter shark bites: A) Fresh; B) Very fresh bite showing characteristic “foaming” and two healed scars; C) Healing bite; D) Two differing stages of healing bites, with the larger bite more recent while the smaller ones almost fully healed. Note the cyamids in the bite wounds of panels C and D (in the large wound and in the two smaller wounds of unknown origin to the right of it).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4808688/v1/0d245bf3ff1fba6ecfbff61e.jpeg"},{"id":63544798,"identity":"ab7be695-baa0-4be7-bc81-375f19b9857d","added_by":"auto","created_at":"2024-08-29 11:08:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":41528,"visible":true,"origin":"","legend":"\u003cp\u003eGeneralised additive mixed model predicted response of the influences of fixed abiotic variables. A) sea surface temperature, B) day of the year, and C) lunar illumination on the probability of fresh bite presence (left hand axis), and the observed presence/absence of bites (right hand axis). Grey shaded areas represent the 95% CI, red dashed lines indicate ranges of lunar illumination for each moon phase using the lunar package (Lazaridis 2015).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4808688/v1/c20f7395b4ed1b1a9921376c.png"},{"id":80081988,"identity":"14adabd9-3dea-41b5-a762-00fcf4bf03f0","added_by":"auto","created_at":"2025-04-07 16:05:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1633521,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4808688/v1/322691b1-6f1c-4891-87d7-93e9ea928414.pdf"},{"id":63544796,"identity":"584b822c-92b7-4dc2-8050-63ddf47cc196","added_by":"auto","created_at":"2024-08-29 11:08:07","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":27061,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-4808688/v1/cd7edb252ae7fa6548d204b1.docx"}],"financialInterests":"","formattedTitle":"Dynamics of foraging interactions between cookiecutter sharks (Isistius spp.) and short-finned pilot whales (Globicephala macrorhynchus) in Hawaiʻi","fulltext":[{"header":"Introduction","content":"\u003cp\u003eUnderstanding the behaviour, distribution and movement patterns of mesopelagic predators can be a challenging undertaking. This can be especially difficult for smaller predators such as sharks from the genus \u003cem\u003eIsistius\u003c/em\u003e. Deemed cookiecutter sharks due to their distinctive feeding behaviour, cookiecutter sharks are small cigar shaped, pelagic squaloid sharks typically no more than 50 cm in length with a short snout and large eyes (Jahn and Haedrich \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). Within the genus there are at least two species, the smalltooth cookiecutter (\u003cem\u003eI. brasiliensis\u003c/em\u003e) and the largetooth cookiecutter (\u003cem\u003eI. plutodus\u003c/em\u003e), with the largetooth distinguished via variation in colouration and fin shape (Garrick and Springer \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1964\u003c/span\u003e; de Figueiredo Petean and R. de Carvalho 2018). Both share similar distributions being found in tropical waters typically from around 20\u003csup\u003eo\u003c/sup\u003eN to 20\u003csup\u003eo\u003c/sup\u003eS and depths down to 3500 m (Strasburg \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1963\u003c/span\u003e; Jones \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1971\u003c/span\u003e; Jahn and Haedrich \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Nakano and Tabuchi \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), however \u003cem\u003eI. plutodus\u003c/em\u003e has only been identified from sporadic identifications, mainly in the Atlantic Ocean (Garrick and Springer \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1964\u003c/span\u003e; de Figueiredo Petean and R. de Carvalho 2018). Cookiecutter sharks have an unusual feeding mode that facilitates the removal of a \u0026ldquo;plug\u0026rdquo; of flesh from their prey, leaving a characteristic crater wound on the animal if the attack was successful and a crescent shaped wound if the full plug of flesh has not been removed (Jones \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1971\u003c/span\u003e; Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Cookiecutter shark prey consists of the majority of large open ocean predators including marine mammals, teleosts, sharks, and large game fish (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Hoyos-Padilla et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Best and Photopoulou \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Wounds from cookiecutter sharks have been described on many cetacean species, both odontocetes and mysticetes, with the exception of those which are resident to polar regions (LeBoeuf \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Bornatowski et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Best and Photopoulou \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Grace et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In Hawaiʻi, cookiecutter bites have been observed on a number of species, both resident and open-ocean, including spinner dolphins (\u003cem\u003eStenella longirostris\u003c/em\u003e) (Norris and Dohl \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), goose-beaked (\u003cem\u003eZiphius cavirostris\u003c/em\u003e) and Blainville\u0026rsquo;s (\u003cem\u003eMesoplodon densirostris\u003c/em\u003e) beaked whales (McSweeney et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), and Hawaiian monk seals (\u003cem\u003eNeomonachus schauinslandi\u003c/em\u003e) (Hiruki et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Due to the limited known distribution of \u003cem\u003eI. plutodus\u003c/em\u003e we presume all bites on Hawaiian cetaceans are from \u003cem\u003eI. brasiliensis.\u003c/em\u003e\u003c/p\u003e \u003cp\u003eDespite their ability to feed on prey much larger than themselves, stomach contents and chemical tracer analysis reveal that the majority of the cookiecutters\u0026rsquo; diet in the central Pacific around Hawaiʻi still consist of smaller micronekton prey such as squid (Carlisle et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Based on catch data and stable isotopes, it is thought that cookiecutter sharks are diel vertical migrators remaining in deeper water during the day and swimming to the surface at night (Jahn and Haedrich \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Nakano and Tabuchi \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). These studies have also provided evidence that cookiecutter sharks are present in Hawaiian waters year-round, but may display seasonal migrations or shifts in diet, being more abundant during the summer and fall months (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Carlisle et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eShort-finned pilot whales (\u003cem\u003eGlobicephala macrorhynchus\u003c/em\u003e), hereafter referred to as pilot whales, are the most frequently encountered cetacean species in and around the main Hawaiian Islands (Baird et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Baird et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). An abundance estimate in 2017 for the Exclusive Economic Zone (EEZ) surrounding the Hawaiian archipelago was approximately 8,000 individuals (Bradford et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), however this estimate does not distinguish between insular or island-associated and pelagic populations (Baird \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Data from extensive satellite tagging and association analyses based on photo-identification has shown that the pilot whale population around the main Hawaiian Islands is divided into three insular communities showing a propensity for slope areas with depths less than 3000 m (Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Baird \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Van Cise et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Kratofil et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). A long-term photo-identification study focused on the eastern community demonstrated that pilot whales off the island of Hawaiʻi have a hierarchical social structure where individuals travel in stable, mixed-sex social units composed of related individuals and that multiple units preferentially associate to form social clusters (Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, Van Cise et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Some pilot whale groups show year-round residency to the area while others termed \u0026ldquo;visitors\u0026rdquo; only used the area occasionally (Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Dive behaviour from depth-transmitting satellite tags in Hawaiʻi revealed that pilot whales dive deepest during the day (31% of dives; mean\u0026thinsp;=\u0026thinsp;666.1\u0026thinsp;\u0026plusmn;\u0026thinsp;16.7 m) but more frequently at night (58% of dives, mean\u0026thinsp;=\u0026thinsp;415.5\u0026thinsp;\u0026plusmn;\u0026thinsp;14.8 m), possibly following vertical prey migrations of Histioteuthid and Onychoteuthid squid (Young \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1975\u003c/span\u003e; Owen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Lunar phase also influenced dive behaviour, with animals diving deeper, longer, and farther from shore during a full moon compared to a new moon (Owen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Dives during the winter months (February \u0026ndash; April) were also deeper, longer, and further from shore than in autumn or summer (Owen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWhen studying cryptic and difficult to observe species, the use of a proxy can be employed to gather data. For example, many specimens of giant squid (\u003cem\u003eArchiteuthis spp\u003c/em\u003e.) are recovered from sperm whale (\u003cem\u003ePhyseter macrocephalus\u003c/em\u003e) stomach contents (Clarke \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1966\u003c/span\u003e; Clarke and Roper \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Santos et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). In this study, the cookiecutter shark bite wounds and scars observed on another species are used as a proxy to provide unique insights into the foraging dynamics of the sharks. Here we use cookiecutter shark bites on pilot whales to assess changes in shark foraging ecology. As our study population of pilot whales are largely resident to Hawaiʻi Island, they remove confounding factors from previous studies using landed pelagic fish as a proxy (e.g. where location of capture is unknown, Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Since previous studies have suggested seasonal movements of cookiecutter sharks in Hawaiian waters (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), we predict that the probability of pilot whales being bitten will be highest in the summer. Furthermore, as noted, pilot whale space use and diving behaviour varies with lunar phase (Owen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). During the full moon, pilot whales are farther offshore and diving deeper, thus we would expect more overlap with cookiecutter sharks during full moons versus the new moon.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy location and photographic data\u003c/h2\u003e \u003cp\u003eThe study was conducted off the leeward (western) side of Hawaiʻi Island over an area of approximately 2500 km\u003csup\u003e2\u003c/sup\u003e, with depths ranging from shallow coastal water to approximately 5000 m. Pilot whale photos were collected from 2003\u0026ndash;2012 as part of a long-term, multi-species assessment of cetaceans in Hawaiʻi (see Baird et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) as well as from opportunistic sightings by the Wild Whale Research Foundation. During directed research surveys, groups were approached for species confirmation, to take photos for individual identification and to collect sighting data, including date, GPS location (lat / long), and group size (min, max, best) (see Baird et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Attempts were made to photograph the right and left sides of every individual in the group regardless of size or distinctiveness level, although this was not always possible due to field limitations such as time of day, Beaufort sea conditions and fuel constraints. A sighting or group was defined using a 1000 m chain-rule where all individuals within 1000 m of other individuals are assumed to be associated (Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Methodology used to process photos for photo-identification is discussed in detail in Mahaffy et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Briefly, photos from each sighting were sorted by individual using unique natural markings on the dorsal fin and were then visually compared to the photo identification catalogue; if a match was found, the individual was added to the catalogue under the existing identification (ID) number (e.g., HIGm####) and if no match was found the individual was assigned a new ID. The best photo from each sighting of an individual was assigned a photo quality rating (1\u0026thinsp;=\u0026thinsp;poor, 2\u0026thinsp;=\u0026thinsp;fair, 3\u0026thinsp;=\u0026thinsp;good, 4\u0026thinsp;=\u0026thinsp;excellent) and the individual was also rated for distinctiveness (1\u0026thinsp;=\u0026thinsp;not distinctive, 2\u0026thinsp;=\u0026thinsp;slightly distinctive, 3\u0026thinsp;=\u0026thinsp;distinctive, 4\u0026thinsp;=\u0026thinsp;very distinctive) when it was added to the catalogue (Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Analyses were restricted to distinctive or very distinctive individuals with good or excellent quality photos. Individual sighting histories in the photo-identification catalogue were used to determine the degree of residency to the island of Hawaiʻi; only pilot whale individuals resident to the island (those recorded in five or more sightings over four or more years (Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e)) were included in the study.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eCookiecutter shark bite analysis\u003c/h2\u003e \u003cp\u003eWithin each sighting of an individual, all relevant photos were used, allowing for the assessment of a larger proportion of the body than visible in a single photograph. Photos were examined to determine cookiecutter shark bite presence, number, and location on the body (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The body was divided into head, mid lateral, dorsal fin, and peduncle sections and further into 10 sections, five of which were below the water line (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). For each sighting of an individual, we recorded which of the five sections above the waterline were visible for each side, to determine the proportion of the body that was available for analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCookiecutter shark bites were distinguished from similarly sized wounds and scars (such as those caused by conspecifics) by their slightly ovoid shape and uniform depth (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and their status were classified as fresh, healing or scarred. Fresh bites were those that were pink or red in colour and/or those which displayed an early immune response such as swelling or \u0026ldquo;foaming\u0026rdquo; (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, b). All bites that were classified as fresh were yet to be colonised by cyamids (whale lice, \u003cem\u003eIsocyamus delphini)\u003c/em\u003e, and are suspected to be less than one week old as cyamid colonisation was often observed within approximately one week of the bite occurring (Mahaffy, \u003cem\u003eunpubl data\u003c/em\u003e). Healing bites were crater-shaped depressions in the issue typically orange in colour due to the presence of cyamids (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb, c). Healing occurs in a number of stages that may range from 4 to \u0026ge;\u0026thinsp;95 days in duration (Gimenez et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Once bites have healed to the point of scarring, the removed flesh is typically replaced with healed, re-pigmented tissue that may have a slightly lighter-coloured halo around the original wound and an uneven appearance around the border (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) (Balbuena and Raga \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Gimenez et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). At this stage of healing, cyamids are absent as conditions for attachment become unsuitable and they typically move back to their usual areas around the mouth and other crevasses in the skin (Balbuena and Raga \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1991\u003c/span\u003e). Scar shapes were similar to those observed by Dwyer and Visser (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), typically forming a round or ovoid convex shape (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Observed scars that had healed in a crescent shape were likely the result of an unsuccessful cookiecutter attack which did not result in the full removal of the typical plug of flesh.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis and modelling\u003c/h2\u003e \u003cp\u003eTo explain spatiotemporal patterns in the presence and absence of bite marks, a combination of abiotic data (date, year, sea surface temperature (SST), lunar phase, lunar illumination (LI)) and data on social clusters were included in the statistical analysis. Weekly average sea surface temperatures were obtained from National Oceanic and Atmospheric Administration (NOAA) using AVHRR Pathfinder Sea-Surface Temperature v5 and v5.1 for the study area (Supplementary Fig S1). The area used for SST was from 19\u003csup\u003eo\u003c/sup\u003eN to 20.25\u003csup\u003eo\u003c/sup\u003eN and from 156\u003csup\u003eo\u003c/sup\u003eW to 158\u003csup\u003eo\u003c/sup\u003eW. Lunar phase and lunar illumination were obtained using the \u003cem\u003elunar\u003c/em\u003e package in R (Lazaridis \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), for each survey date. Phases were combined into five groups combining similar illumination: waxing crescent and waning crescent were combined, as were waxing gibbous and waning gibbous, as per Owen et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Seasons were grouped into autumn (November to January), Winter (February to April), Spring (May to July), and Summer (August to October) as per Flament et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). As individuals within the same social cluster are likely to experience similar exposure to cookiecutter sharks, social cluster (from Mahaffy et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e)) was included in subsequent analyses. In order to investigate the distribution of fresh bites across a pilot whale\u0026rsquo;s body, a comparison of the observed versus expected number of bites was conducted based on the proportion of the body area seen (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Fresh bite proportions for each location were calculated and adjusted for whether one or both sides of the body were seen. A chi-squared test was performed using R to compare observed and expected, assessing deviations from the expected distribution based on the body area seen.\u003c/p\u003e \u003cp\u003ePresence or absence of fresh bites for each animal in each sighting were modelled in R Statistical Software (v4.2.2; R Core Team \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) using generalised additive binomial mixed models (GAMM) with a complementary log-log link due to zero inflated data. GAMMs were applied using \u003cem\u003eGamm4\u003c/em\u003e (Wood and Scheipl \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Modelling was undertaken with temperature, lunar phase, lunar illumination, and Julian date being used as explanatory variables, with pilot whale social cluster included as a random effect to account for potential grouping of data. A likelihood ratio test was conducted to assess effectiveness of the inclusion of the random effect, and Spearman\u0026rsquo;s rank correlations were used to test for collinearity. The best fitting model was selected using a forward stepwise model selection (Zuur et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), based on Akaike information criterion (AIC) scores of the underlying generalised linear model of the GAMM (Supplemental Table\u0026nbsp;1). The percentage of the pilot whale visible had an exponential relationship with the percentage of animals observed with fresh bites, therefore this was added to the model as an offset. Model accuracy was tested using K-fold cross validation using the caret package in R (Kuhn \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003ePhotos from 403 individual pilot whales from 16 social clusters were examined. Photos were obtained from a total of 5871 identifications (i.e., repeated encounters of individuals). Identifications were distributed roughly similarly across lunar phases (ranging from 282 to 382 identifications). There were similar numbers of identifications available from the Hawaiian winter (348), spring (383), and summer (321), but fewer (207) available from the Hawaiian autumn. Bites of various stages were observed on 396 of the 403 individuals (98.3%). A total of 169 fresh bites were recorded on 115 individuals, representing 161 identifications. Of the 115 individuals with fresh bites, most (108) had only a single fresh bite, six had two fresh bites, and one had three fresh bites. There were 575 healing bites recorded on 211 individuals, representing 490 identifications, while 8549 scars were recorded on 389 individuals, representing 2779 identifications. There were occurrences of whales having more than one healing bite, but it could not be determined if the bites occurred relatively close in time (e.g., during the same day or week). Many individuals had multiple bites in varying states of healing/re-pigmentation. The mean proportion of the body seen during each sighting was 22.2% (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0), therefore more bites were likely present but unobservable due to being below the waterline. Most fresh bites recorded were located on the head (33.1%), lateral sides of the body (29%) and peduncle area (26.6%) while the dorsal fin had the lowest percentage of fresh bites (just over 10%) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLocation of fresh cookiecutter shark bites on short-finned pilot whales. Comparisons of observed versus expected fresh bites by location.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e% of bites by location\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e Observed\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e Expected\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDorsal Fin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHead\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLateral\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeduncle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePearson\u0026rsquo;s Chi-sq\u0026thinsp;=\u0026thinsp;9.3348, df\u0026thinsp;=\u0026thinsp;3, p value\u0026thinsp;=\u0026thinsp;0.02515\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWhen taking the area of each section of the body into account and whether one or both sides were photographed during a sighting, there was a greater than expected number of bites on the head (\u003cem\u003eX\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;9.33, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.025) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), and a lower than expected number of bites on the peduncle. Healing bites and scars were observed in every month of the year, and fresh bites were observed in all months except September (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u0026ndash; Breakdown of total cookiecutter bites on short-finned pilot whales by status of bite and month of year\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMonth\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal Individuals\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTotal Identifications\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTotal Fresh bites\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTotal Healing Bites\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTotal Scarred bites\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eJanuary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e87\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFebruary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMarch\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e155\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e160\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApril\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e315\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e139\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1815\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMay\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e263\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e589\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1285\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eJune\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eJuly\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e356\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1117\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1732\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAugust\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e284\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e622\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1248\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSeptember\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e125\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e247\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e204\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOctober\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e156\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e379\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e551\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNovember\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e127\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e523\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e675\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecember\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e553\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e734\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2143\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5871\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e170\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e575\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8549\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe GAMM showed that the predicted binomial presence/absence was influenced by surface temperatures, Julian day of the year and lunar illumination as smooth terms, including an offset of the percentage of the body viewed in each sighting plus the social cluster of the animal in question as a random effect (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). There was a decreased likelihood of fresh bites at higher temperatures (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Day of the year also influenced the likelihood of fresh bites with three distinct peaks centred around the 115th, 200th and 290th days of the year approximately corresponding to late April, mid-July, and mid-October (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). The first peak in bite probability at day 111 was the lowest peak with whales showing a probability of fresh bite occurrence of 0.04 (SE\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008). The second peak at day 201 was 0.05 (SE\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009), and the third peak of 0.06 (SE\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01) occurred on day 284. Lunar illumination also showed a significant influence with increases in the probability of fresh bites during the transition between crescent moon and quarter (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). Year was also tested as a random effect, but the value was too close to zero to be effective as a random effect.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of model of best fit for effects of abiotic variables on the prevalence of fresh cookiecutter bites on short-finned pilot whales. Coefficients and diagnostics (Chi-sq and P-values) indicate the effect of each parameter level.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003edf\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ep-value\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRMSE\u003c/b\u003e: 1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eParametric Response Variable\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSD\u003c/b\u003e: 0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSea surface temperature\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eNon-parametric Response\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLunar illumination\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e141.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.816\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eJulian Date\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e313.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.530\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe inclusion of pilot whale social cluster in the model significantly improved model accuracy (\u003cem\u003eΧ\u003c/em\u003e\u0026sup2;= 853.07, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), indicating the presence of cluster-specific effects. However, the variance component for the random effect (cluster) was estimated to be 0.355 (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;0.59), indicating high variability among clusters in the latent scale of the complementary log-log model. The intraclass correlation coefficient (ICC) was approximately 0.097, suggesting that around 9.7% of the variability in the presence or absence of fresh bites could be attributed to differences between clusters.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur results show that probability of cookiecutter bites on resident pilot whales varies by season, lunar phase, and water temperature. In this study we obtain additional understanding of cookiecutter shark foraging ecology (and their interaction with a marine mammal prey species) by using bite wounds on free-swimming pilot whales. Unlike previous studies, which relied on dead pelagic fish brought to port, by observing free-swimming pilot whales we know the approximate geographic area where bites took place (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). We estimate that fresh bites observed on pilot whales likely occurred within one week of the individual being photographed, and therefore interactions almost certainly took place waters off the west side of Hawaiʻi Island. By concentrating on a resident cetacean population, we could determine how the probability of fresh bites varied based on both abiotic conditions and season.\u003c/p\u003e \u003cp\u003eStable isotopes analyses of the livers and muscles tissues of cookiecutter sharks suggest that cookiecutter sharks exhibit seasonal shifts in diet, or in the location where they forage (Carlisle et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). We observed a general seasonal occurrence in fresh bites. While there was an overall increase in bite probability in April, the number of bites were not consistent, showing zero fresh bites in September and lower numbers of bites in May and August (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Cookiecutter shark bite probability peaked in October (Julian day 290) but was lowest during the winter months (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). There were troughs between the peaks where virtually no pilot whales were observed. Why these reductions in pilot whale sightings occurred is unclear, but it was impossible to measure bite probability during these periods. The probability of fresh cookiecutter bites on bigeye tuna (\u003cem\u003eThunnus obesus\u003c/em\u003e), the majority of which were caught within the Hawaiʻi EEZ, similarly peaks from October-December (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Swordfish (\u003cem\u003eXiphias gladius\u003c/em\u003e) are primarily caught outside the Hawaiian EEZ and show a peak in fresh bites from March-May (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Combined these results suggest either that cookiecutter sharks show seasonal shifts in their diet or display seasonal migrations moving away from the main Hawaiian Islands in the winter and returning in the late spring.\u003c/p\u003e \u003cp\u003eThe diet of cookiecutter sharks in Hawaiʻi includes squid (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Carlisle et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), which is also prey for pilot whales, suggesting the potential for competitive interactions between sharks and pilot whales (Seagars and Henderson \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Sinclair \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). A high biomass of vertical diel migrating micronekton, including squid, occurs off the west coast of Hawaiʻi Island, and the distance from shore also changes in relation to day and lunar phase (Benoit-Bird et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Pilot whales in Hawaiʻi dive deeper during the day (mean\u0026thinsp;=\u0026thinsp;666 m) than at night (mean\u0026thinsp;=\u0026thinsp;415 m), although they perform more dives at night, and this variation may increase the rate at which pilot whales are encountering cookiecutter sharks as they move into shallower waters at night following the vertical diel migrating micronekton. Our data shows an increase in shark bite probability peaking in the transition from crescent to quarter moon (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e); this may either be a product of overlapping use of the vertical water column, or, as pilot whales in Hawaiʻi have been observed to move farther offshore as lunar illumination increases, an indication of movement into an area occupied by more cookiecutter sharks (Owen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePilot whale social structure may influence the dynamics of interaction between the two study species, and model predictions had a high standard deviation, suggesting that there is substantial variation in the effect across social cluster. Pilot whales in Hawaiʻi are known to have a social structures characterized by strong, long-term associations, suggesting individuals from the same social groups are exposed to cookiecutter sharks at similar rates and should may therefore have similar numbers of bites (Alves et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Mahaffy et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). This may suggest cookiecutter sharks show heterogeneity in their distribution and that pilot whales within a group are more likely to get bitten when they move through a high-density cookiecutter shark area.\u003c/p\u003e \u003cp\u003eSea surface temperature showed a significant effect on the probability of pilot whales being bitten, with bite probability decreasing as SSTs increased. Based on trawl data from the north Pacific, cookiecutter sharks were caught at temperatures ranging from 18\u003csup\u003eo\u003c/sup\u003eC to 26\u003csup\u003eo\u003c/sup\u003eC (Nakano and Tabuchi \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). We recorded no fresh bites on pilot whales in September, the month with the highest average temperatures (27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35 \u003csup\u003eo\u003c/sup\u003eC), despite 125 individuals being photographed from nine different sightings. Water temperatures off Hawaiʻi are relatively stable but these results further suggest that cookiecutter sharks may avoid surface waters\u0026thinsp;\u0026gt;\u0026thinsp;26\u0026ndash;27\u0026ordm;C, although this assumes that sharks are biting pilot whales at the surface. The probability of fresh bites also changes with lunar illumination, with a peak occurring between crescent and gibbous moon phases (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The increases in bite prevalence on pilot whales during these times may be attributed to changes in the lunar movement of micronekton or the pilot whales themselves. Micronekton in the mesopelagic boundary community increase their depth and move farther offshore during periods of high lunar illumination (Benoit-Bird et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Abecassis et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Prihartato et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Comfort et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Increased surface illumination may also impact cookiecutter shark ability to hunt in surface waters or attract prey (Widder \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Finally, pilot whales dive shallower and for shorter durations during the Quarter and Crescent lunar phases, which may cause them to spend more time in the near-surface waters where they may be more susceptible to cookiecutter shark bites (Owen et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). We would predict that bites are more likely to occur at the surface due to the amount of time cookiecutter sharks and pilot whales spend there relative to deeper depths (as pilot whales are only diving below the surface for relatively short periods of time).\u003c/p\u003e \u003cp\u003eCookiecutter sharks appear to show some selection for biting the head and dorsal areas of pilot whales, while avoiding or randomly biting the lateral and peduncle areas. However, in studies involving both odontocetes and mysticetes there were higher numbers of cookiecutter bites on the peduncle of mysticetes in comparison to odontocetes (Best and Photopoulou \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In other species, such as rough-toothed dolphins (\u003cem\u003eSteno bredanensis\u003c/em\u003e), examination of the ventral side was facilitated through their aerial behaviour and this area was often covered in cookiecutter scars (Baird \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Unfortunately, pilot whales rarely leap out of the water and examination of the ventral side was therefore not possible, although some records of underwater sightings were obtained. Hence, our estimates of bite probabilities on short-finned pilot whales are conservative.\u003c/p\u003e \u003cp\u003eWe provide new insight into the foraging dynamics of cookiecutter sharks, an incredibly versatile pelagic predator whose bites are ubiquitous on pelagic predators in tropical waters. By using bites on free-swimming pilot whales, we can approximate the geographic location where bites occurred, unlike previous studies with pelagic fishes which could only approximate bite location to the Hawaiian Islands (Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). While cookiecutter shark bites on pilot whales may not be fatal (although some small dolphins may die from bites that penetrate into the abdominal cavity, Baird \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), they may still reduce pilot whale fitness. Due to their potential high abundance, and ability to play an important ecological and economic role (e.g., cookiecutter shark bites reduce the price of market fish at auction, Papastamatiou et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), additional studies of cookiecutter shark foraging dynamics are warranted.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompliance with Ethical Standards\u003c/h2\u003e\n\u003cp\u003eThe authors declare no conflict of interest. Data were collected under NOAA Fisheries Scientific Research Permits 731-1509, 731-1774, and 15330 issued to RWB, and research methodologies were approved by the Cascadia Research Collective Institutional Animal Care and Use Committee.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eAcknowledgments\u003c/h2\u003e\n\u003cp\u003eFunding for field work during which photos were obtained was provided by the Wild Whale Research Foundation, Cascadia Research Collective, Southwest Fisheries Science Center (SWFSC), Pacific Islands Fisheries Science Center, and Chief of Naval Operations/Environmental Readiness Division. The authors would like to thank D. Bailey, A. MacGregor, S. Elliott, and J. Clarke from the University of Glasgow for all their help and support. All the staff at Cascadia Research Collective, Olympia, Washington including but not limited to A. Allen, A. Douglas, N, Harrison, J. Welsh and the rest of the whole team whose help and advice was immeasurable.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eData Availbility Statement\u003c/h2\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available in the Zenodo repository, [https://doi.org/10.5281/zenodo.12733235]. The code used for analysis is available on GitHub, [https://github.com/NWMilne/Cookiecutters/tree/v1.0.1]. These resources are accessible and comply with the repository\u0026apos;s data policies.\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003efor field work during which photos were obtained was provided by the Wild Whale Research Foundation, Cascadia Research Collective, Southwest Fisheries Science Center (SWFSC), Pacific Islands Fisheries Science Center, and Chief of Naval Operations/Environmental Readiness Division. The authors would like to thank D. Bailey, A. MacGregor, S. Elliott, and J. Clarke from the University of Glasgow for all their help and support. All the staff at Cascadia Research Collective, Olympia, Washington including but not limited to A. Allen, A. Douglas, N, Harrison, J. Welsh and the rest of the whole team whose help and advice was immeasurable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbecassis M, Polovina J, Baird RW, Copeland A, Drazen JC, Domokos R, Oleson E, Jia Y, Schorr GS, Webster DL, Andrews RD (2015) Characterizing a foraging hotspot for short-finned pilot whales and Blainville's beaked whales located off the west side of Hawaiʻi Island by using tagging and oceanographic data. 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Springer, New York, pp 323\u0026ndash;341\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"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":"Cookiecutter, foraging, Hawaiʻi, pilot whale, shark","lastPublishedDoi":"10.21203/rs.3.rs-4808688/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4808688/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCookiecutter sharks (\u003cem\u003eIsistius spp.\u003c/em\u003e) are small pelagic squaloid sharks found throughout tropical and sub-tropical waters that are known to feed opportunistically on a range of prey, including animals much larger than themselves. Short-finned pilot whales (\u003cem\u003eGlobicephala macrorhynchus\u003c/em\u003e) are resident to Hawaiʻi Island and are often observed with fresh and healed cookiecutter shark bites. In this study, cookiecutter bites were used to infer the spatiotemporal patterns of the foraging behaviour of sharks on pilot whales. Data were gathered off the Hawaiian Islands, within coordinates:(21\u0026deg;N, 158\u0026deg;W) to (18.5\u0026deg;N, 154.5\u0026deg;W). A photo-identification catalogue of 403 resident short-finned pilot whales (representing 5871 identifications of known individuals from 365 encounters from 2003\u0026ndash;2012), were used to infer the prevalence and seasonal variation in shark presence. The mean proportion of the pilot whale\u0026rsquo;s body visible for documenting shark bites was 22.2% (SD\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0). A total of 9293 fresh, healed, and scarred bite marks were documented on 396 of 403 whales (97.8%). Bites were most frequently documented on the head (33.1% of all bites), followed by the lateral sides (29.0%) and peduncle (27.2%), while the dorsal fin had the lowest percentage of bites (10.7%). The presence of fresh bites varied with day of the year, with peaks in April, July and mid-October and were also negatively correlated with sea surface temperature. There was also a peak in fresh bites in the transition between crescent and quarter lunar phases. These results provide further evidence that cookiecutter sharks in Hawaiʻi may perform seasonal migrations or dietary shifts.\u003c/p\u003e","manuscriptTitle":"Dynamics of foraging interactions between cookiecutter sharks (Isistius spp.) and short-finned pilot whales (Globicephala macrorhynchus) in Hawaiʻi","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-29 11:08:03","doi":"10.21203/rs.3.rs-4808688/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revise and Resubmit","date":"2024-09-06T15:02:02+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-08-13T04:39:19+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-08-02T21:35:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-30T09:36:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Marine Biology","date":"2024-07-26T10:17:37+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":"35446615-f714-4b6b-8ad8-3895900e092d","owner":[],"postedDate":"August 29th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-04-07T15:59:27+00:00","versionOfRecord":{"articleIdentity":"rs-4808688","link":"https://doi.org/10.1007/s00227-025-04633-4","journal":{"identity":"marine-biology","isVorOnly":false,"title":"Marine Biology"},"publishedOn":"2025-04-01 15:57:05","publishedOnDateReadable":"April 1st, 2025"},"versionCreatedAt":"2024-08-29 11:08:03","video":"","vorDoi":"10.1007/s00227-025-04633-4","vorDoiUrl":"https://doi.org/10.1007/s00227-025-04633-4","workflowStages":[]},"version":"v1","identity":"rs-4808688","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4808688","identity":"rs-4808688","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}