Orca (Orcinus orca) prey-handling and harassment of southern right whales (Eubalaena australis) in Península Valdés, Argentina

Orca (Orcinus orca) prey-handling and harassment of southern right whales (Eubalaena australis) in Península Valdés, Argentina | 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 Article Orca (Orcinus orca) prey-handling and harassment of southern right whales (Eubalaena australis) in Península Valdés, Argentina Virginia Mailen Tortolini, María Constanza Marchesi, Eva Camila Tavano Formigo, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7880511/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract We report the first video-documented case of orca ( Orcinus orca ) cooperative prey-handling and feeding behavior on a southern right whale (SRW, Eubalaena australis ) calf carcass, along with harassment events and whale responses, recorded in the Natural Protected Area El Doradillo in Península Valdés, Argentina. Drone footage and shore-based observations were conducted on September 5, 2025, revealing an orca group refloating and feeding on a sunken whale calf carcass. The orca group consisted of six identified individuals from the Península Valdés population. Drone footage (total recording time: 1 h 37 min) showed coordinated behavior among orcas, who alternated in holding, lifting, and releasing the carcass, suggesting cooperative handling. The orcas engaged in forty-six harassment events targeting southern right whales, especially mother–calf pairs. Defensive responses described as 360° turns and zigzag pattern were elicited more often when orcas approached from the latero-caudal angle with respect to SRW head. These results expand the knowledge on the behavioral ecology of this orca population and underscore the ecological significance of orca–right whale interactions in one of the most important SRW breeding grounds in the Southwestern Atlantic Ocean. Biological sciences/Ecology Earth and environmental sciences/Ecology Biological sciences/Zoology Killer whale harassment cooperative feeding predator-prey interactions behavioral responses drone footage Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The orca ( Orcinus orca ), or killer whale, is the largest extant dolphin and a top predator in all ocean basins [ 1 ]. Although considered a generalist predator, different populations exhibit specific prey preferences and hunting strategies, often associated with acoustic repertoires and morphological characteristics, leading to the differentiation of several ecotypes worldwide [ 2 ]. These ecotypes are commonly classified as fish- or marine mammal-eaters, though the distinction is not absolute, as fish-eating populations are known to prey on marine mammals and vice versa [ 3 ]. Globally, orcas prey on at least eighteen species of cetaceans, including the largest baleen whale, Balaenoptera musculus [ 4 ]. Orca predation on baleen whales (Mysticetes) occurs across multiple oceans, including the North Pacific, South Pacific, Indian, and Southern Oceans [ 5 ], and is thought to influence prey abundance, distribution, behavior, and evolution [ 5 , 6 , 7 ]. For example, orcas significantly affect gray whale ( Eschrichtius robustus ) calf survival and migration patterns [ 7 , 8 ]. Similarly, bowhead whales ( Balaena mysticetus ) exhibit pronounced and prolonged behavioral responses to orca predation risk, which may reduce their fitness and indicate ecological impacts beyond direct mortality [ 9 ]. While orca predation on baleen whales is globally recognized, its occurrence in the South Atlantic Ocean, particularly along the Argentine coast, remains poorly documented. The orca population of Península Valdés (Chubut, Argentina) is best known for its unique foraging strategy of intentionally stranding on beaches to capture South American sea lions ( Otaria flavescens ) and South American elephant seal ( Mirounga leonina ) pups, a culturally transmitted technique passed across generations [ 10 , 11 , 12 ]. Although pinnipeds are their main prey, orcas in this region also consume sharks, rays and possibly tuna [ 13 , 14 ]; as well as dusky dolphins ( Aethalodelphis obscurus; [ 15 ] [ 16 ]. Regarding this orca population, previous opportunistic observations of predation events on baleen whales have been reported. In Península Valdés, a confirmed attack occurred in 1971 [ 17 ], and numerous interactions were later reported [ 18 ]. Between 1972 and 2000, 117 encounters between orcas and SRWs were documented, 12 of which were classified as attacks, characterized by intense activity from both species, bite marks on the whales, and visible blood or blubber pieces at the surface [ 18 ]. Globally, similar attacks on SRW calves have been documented in southern Brazil [ 19 ] and other regions [ 5 , 20 ]. Península Valdés is a critical area for both SRW and orcas. It serves as a major breeding and calving ground for SRWs, which aggregate in the sheltered Nuevo and San José gulfs and adjacent coastal areas from late autumn to late spring (May-December) [ 21 , 22 ]. Orcas, by contrast, occur year-round but are more frequently observed outside the gulfs, particularly at Punta Norte and Caleta Valdés, during late austral spring and summer, coinciding with the reproductive season of their main prey [ 10 , 23 ]. Nonetheless, orcas occasionally enter the gulfs, where their presence overlaps spatiotemporally with that of SRW, increasing the likelihood of predator-prey interactions. Despite the ecological significance of orca predation on baleen whales, our understanding of this phenomenon in Argentina remains limited. In particular, little is known about how orcas in this region handle, feed on, and share cetacean carcasses. Here, we combine shore-based observations with drone footage to provide the first detailed description of orca prey-handling and feeding behavior following the hunting of a SRW calf, alongside repeated harassment events, and the whale’s behavioral responses near Península Valdés. Results The orca group was first sighted at 11:20 local time (UTC-3), when dorsal fins were observed through binoculars breaking the sea surface approximately 2 km offshore from our vantage point, Punta Ameghino cliff (Fig. 1 ). A drone was launched at 11:33, arriving to the area shortly after and confirming the presence of six orcas (Fig. 2 ). The group comprised Jazmín (PTN-002, female, born in 1991), her recent calf (unnamed, believed to be male, first sighted in June 2024), and two older offspring, Auka (PTN-029, sex unknown, born in 2016) and Morgan (PTN-036, sex unknown, born in 2002), as well as Jazmín ’s sister, Llen (PTN-010, female, born in 2000) and her daughter, Shotel (PTN-026, female, born in 2014). When the drone reached the group (11:39), no southern right whales (SRWs) were detected within a 500 m radius. The orcas were actively performing short vertical dives and subsurface circling in a restricted area, without any evidence of feeding behavior. After almost ten minutes (11:48), Jazmín ’s calf surfaced carrying a small, red-colored piece of flesh in its mouth (Fig. 3 a). The group continued performing short dives for approximately eight minutes, until Jazmín refloated a SRW calf carcass (11:56) from an estimated depth of 10 m (Fig. 1 ). The orcas were thus feeding on a sunken whale calf. Cooperative prey-handling and feeding behavior Upon bringing the carcass to the surface, Jazmín maintained its grip by holding a torn piece of skin, preventing it from sinking. The other group members gathered around, actively biting off pieces of tissue. The carcass appeared fresh and well preserved; both fluke tips were missing and bore clear bite marks, while the head and pectoral fins remained intact (Fig. 3 b, c). The carcass was open on the lateroventral side, exposing blood and blubber (Fig. 3 c). From the moment the carcass was refloated and throughout the main event (total duration 1 h 29 min), the orcas maintained a relatively stationary position, refloating and allowing the carcass to sink twice. No adult or calf SRWs were observed nearby, and those within a radius of 500 m, did not show evidence of disturbance. The orcas appeared to coordinate their actions, apparently, taking turns to keep the carcass at or near the surface. Larger individuals held the carcass by strips of peeling skin or by the pectoral fin, while others positioned themselves underneath to lift it (Fig. 3 d). At times, individuals were observed intentionally pushing the carcass to greater depths and allowing it to sink. After approximately two minutes of such behavior, they released the carcass and resumed short vertical dives, surfacing with pieces of tissue in their mouths (Fig. 3 e). A second refloating event occurred at 12:06, during which the orcas continued removing skin in the upper few meters of the water column (Fig. 3 f). For the next 41 minutes, orcas repeatedly surfaced with strips of skin in their mouths, peeled the carcass, and shared prey (Fig. 3 g, h). Jazmín remained closely associated with her calf, who occasionally swam alone or with Morgan . While swimming in parallel, the calf repeatedly attempted to obtain pieces of prey directly from its mother’s mouth and occasionally from Morgan ’s (Fig. 3 i). At one point, one orca held the carcass below the surface while another was observed inspecting the carcass’ mouth, placing its head inside it (Fig. 3 j). By 12:47, Shotel was manipulating the prey alone until it detached a piece of skin and swam away, leaving the carcass to the other. For approximately 30 min thereafter, only five orcas interacted with the carcass while one individual remained out of sight. During this time, the carcass was completely stripped of skin from the posterior head region to the tailstock (Fig. 3 k), and the orcas were seen feeding and sharing internal organs (Fig. 3 l). At 13:18, the orcas began moving northward along the coast, leaving the carcass behind. The final observation of feeding occurred at 13:28, when Jazmín and her calf were seen carrying and sharing an organ. By that time, the group was approximately 2 km from the carcass, marking the end of the main prey-handling event at 14:01. Harassment and whale responses Between 14:15 and 15:51, a total of 46 orca harassment events directed towards 90 SRWs were recorded. Of these events, 34 elicited active reactions from whales (Table 1 ). Two main reaction types were identified: a “360° turn” and a “zigzag pattern” (see description below; Fig. 4 a, b). Most harassment events targeted mother-calf (MC) pairs (Table 1 ), and although all six orcas participated, one individual separated carried out most approaches alone. In 35 of the 46 events, no physical contact occurred. The whales showed no anticipatory response to the orcas’ approach in any of the 46 harassment events. Table 1 Total number of harassment events categorized by whale reaction type and group composition. BG: breeding groups; MC: mother–calf pairs, NS: non-social groups; SI: solitary individuals; No: No reaction. Reaction Group composition 360° turn Zigzag No Total NS 2 2 3 7 IS 5 1 1 7 MC 16 8 7 31 BG 0 0 1 1 Total 23 11 12 46 The “360° turn” reaction involved a 360° full body turn of the whale upon close approach or physical contact by the orcas (Fig. 4 a). This movement occurred in the horizontal plane, rather than as a roll along the whale’s longitudinal axis and was observed in all group categories except breeding groups (BG) (Table 1 ). Among MC pairs, the mother’s responses were immediate, turning rapidly and positioning their calves inside the circle. In a few cases, calves positioned themselves either on top of the mother’s back or outside the circle. The “zigzag pattern” reaction consisted of a strong lateral undulation of the body, resembling a snake-like motion, with the body forming an “S” shape (Fig. 4 b). These movements involved vigorous tail swings, occasionally producing tail slaps. Although less frequent, this reaction was observed in all group categories except BG (Table 1 ). Most harassment events involved a latero-caudal approach (N = 28) rather than latero-frontal (N = 6) (Fig. 5 ). The whale’s behavioral response was not independent of the direction from which the orcas approached. Considering both directions and both responses (360° turn and zigzag), whales reacted differently. Orcas were prone to approach from the latero-caudal direction and elicited a 360° turn more often than expected by chance (Chi-squared test, p = 0.008), whereas both responses were equally probable when the approach was latero-frontal. In twelve cases, no whale behavioral response was observed (Table 1 ). These included one BG (1 Female + 2 Males), three non-social groups (NS; 1 MC pair + 1 adult; 2 adults; and 3 adults), one solitary individual (SI), and seven MC pairs. Orca approaches occurred from both directions: nine latero-caudal, and three latero-frontal. Despite close proximity, no physical contact was observed between the species. Discussion This report provides the first video-documented evidence of orca prey-handling and feeding on a southern right whale (SRW) in the Southwestern Atlantic Ocean. It also documents multiple harassment events carried out by the same group in a single day, along with the defensive responses by SRWs. Together, these observations provide new insights into orca predatory behavior and whale defense strategies in Patagonia. The feeding event we report involved a SRW calf, consistent with previous observations of orca predation on large cetaceans [ 5 , 7 , 29 ]. Six identified orcas were observed feeding on a sunken SRW calf carcass, which they repeatedly refloated to the surface. Although the hunting was not witnessed, the carcass appeared fresh and well-preserved, suggesting that the calf had been killed probably hours before our arrival. According to park rangers from the protected area, the group had been observed nearshore earlier that morning, disappearing shortly afterwards (Maria Cabrera, pers. comm.). Several characteristics of the carcass suggest prior orca predation. Both fluke tips were missing and bore clear bite marks, implying that orcas disabled the whale's primary propulsion organ, the tail, thus reducing its capacity to perform defensive tail slaps or escape through rapid swimming. The fluke’s soft, boneless tissue also makes it easier to bite than the bony pectoral fins, which were intact. Similar selective feeding on accessible, soft tissue, especially tongues, has been reported in other cetacean prey [ 30 ]. While one individual was seen inserting its snout into the carcass’s mouth, no direct evidence of tongue consumption was found. Orca predation on cetaceans is often constrained by the rapid sinking of carcasses into waters deeper than 400 m, therefore limiting consumption to soft tissues such as the tongue and lips due to inaccessibility (e.g., [ 30 , 31 ]). In contrast, the event reported here occurred in shallow waters (~ 10 m), allowing prolonged access and extensive exploitation of the carcass, including skin, blubber, muscles, and internal organs. Similar behavior has been described in mammal-eating transient orcas in the Northeastern Pacific Ocean, where food-storing behavior and prolonged feeding on grey whale calves' sunken carcasses occurred in shallow waters (between 15 and 75 m deep; [ 7 ]). Cooperative prey-handling was evident throughout the event. Larger individuals coordinated efforts to keep the carcass near the surface, alternatively gripping strips of skin or lifting it from below. Instances of prey-sharing were also recorded, including mouth-to-mouth transfers, a behavior previously described for this species [ 11 , 16 , 32 ]. These observations highlight both the social complexity and cooperative strategies involved in orca prey use [ 33 ]. Moreover, the prey-sharing behavior observed here between the youngest calf, its mother and sibling likely plays a role in the learning process of communal hunting, as described in other populations [ 34 , 35 ]. Additionally, this observation suggests that calves in this population may begin supplementing milk with solid food early in life, reflecting a transitional or mixed diet similar to that of orcas from the Northeastern Pacific Ocean [ 36 ]. The harassment events occurred within a SRW nursery area and were primarily directed at mother-calf (MC) pairs. These groups are both the most abundant and the most vulnerable in the area due to calves’ small size and limited diving capacity [ 7 , 37 , 38 ]. The 360° turn response observed in mothers appears to be a defensive maneuver positioning the calves at the center of a protective circle, thus reducing orca access. In contrast, the zigzag response, involving vigorous lateral tail movements, may act as an active deterrent, with potential to strike or stun approaching orcas [ 18 ]. Most orca approaches were latero-caudal, effectively exploiting the whales’ reduced visual field and blind spots (i.e., located along the body’s longitudinal axis, directly anterior and posterior to the body). Mysticetes have laterally positioned eyes, each providing a ~ 130° panoramic view, but independent ocular movement and optic nerve anatomy, along with their large heads, limit binocular vision and create a blind zone directly ahead [ 39 ]. Thus, defensive strategies such as lateral undulations or 360° rotations may help whales bring predators into view. Additionally, the absence of whales’ anticipatory responses suggests that the orcas were acoustically silent during the harassment events, consistent with the behavior of mammal-eating transient orcas, which are generally silent while foraging [ 37 , 40 ]. This indicates that whales may rely primarily on vision, rather than hearing, to detect and avoid such predators [ 41 ]. Although grouping during orca attacks has been observed in large whales [ 42 , 43 , 44 , 45 ] and collective defense, such as the “rosette” or “marguerite” formation, has been previously described for SRWs [ 5 , 18 ], they were not observed in this study. This may reflect the short duration of harassment events and their failure to escalate into full predatory attempts. In this context, the multiple harassments of SRW may represent exploratory or training behavior. As they occurred after the main feeding event, harassment may not have been motivated by foraging but rather associated with orca social learning or practice. This is consistent with the well-documented intentional stranding behavior in this population, a culturally transmitted practice through which juveniles acquire skills by observing and participating [ 10 , 11 ]. In the events reported here, the orcas were observed spending most of their time in waters shallower than 10 m. In some regions, whales may use shallow waters as a refuge from orca attacks, as these restrict the directions of attack and pose a stranding risk for orcas [ 7 ]. This strategy has been proposed as a defense for SRWs in Península Valdés [ 5 ]. However, we suggest that this would not be a successful strategy against attacks from this particular orca population, as they regularly operate in very shallow waters when intentionally beaching to capture pinnipeds [ 10 ]. Therefore, the shallow environment would not constrain the orcas, instead it may increase stranding risk and reduce the range of defensive options for SRWs in this area. Ecological conditions may have influenced the observed behaviors. The 2023 outbreak of a highly pathogenic avian influenza (HPAI H5N1) caused severe mortality in the South American elephant seal population, killing ~ 97% of newborn pups and significantly reducing adult numbers [ 46 ]. Population size has since declined by 60%. South American sea lion colonies at Península Valdés were also heavily affected [ 47 ]. By contrast, on August 19, 2025 SRW aerial census recorded a historic peak of 2,110 individuals, including 826 newborns (LAMAMA, unpublished data). This imbalance in prey availability may have encouraged orcas to harass and exploit whales more frequently. Stable isotope analyses from this orca population support such dietary flexibility, showing structuring consistent with seasonal prey fluctuations and individual dietary preferences [ 14 ]. The observations presented here reinforce the ecological significance of orcas as apex predators in northern Patagonia, capable of rapidly adapting their foraging strategies to changing prey landscapes. From early August to mid-October 2025, at least two other predation events on SRW calves were directly observed, while one additional stranded carcass bore confirmed signs of orca predation and three showed evidence of potential orca predation (Programa de monitoreo sanitario Ballena Franca Austral, PMSBFA pers. comm.). Therefore, the number of calves killed by orcas would rise to at least seven. Although likely an underestimate, these events suggest an increasing interaction frequency between orcas and SRWs. If such events become more common, it could affect SRW calf survival, distribution, and behavior, with potential demographic consequences. As top predators, orcas can exert cascading effects in marine ecosystems [ 6 , 48 , 49 ]. Continuous monitoring of orca–SRW interactions will be essential for understanding these predator-prey dynamics and their implications for the SRW population in the region. Methods This report is based on shore-based observations conducted on September 5, 2025, within the Natural Protected Area El Doradillo (Fig. 1 ). The orca group was first detected using binoculars from Punta Ameghino cliff, 20 m above sea level. Continuous visual monitoring began at 11:20 local time (UTC-3) and continued until 16:00 supplemented by drone footage. By the end of the observation period, our position had shifted to Punta Prismático cliff, 25 m above sea level (Fig. 1 ). Drone flight tracks documented the orca’s movements along the coast throughout the observation period (Fig. 1 ). Drone footage was obtained using a DJI Mavic 4, 6K 28mm & 4K 70mm equivalent cameras, operated under calm wind conditions. Due to drone battery and memory card limitations, uninterrupted recording was not possible. Consequently, behavioral descriptions were derived from both drone footage (total recording time: 1 h 37 min) and direct visual observations made by the authors. Video footage was analyzed independently by two of the authors (V.M.T. and E.C.T.F.). Orca behavior was assessed using the focal group follow protocol with ad libitum event recording [ 24 ]. Analyses focused on prey-handling and harassment behaviors, as well as the reactions and defensive responses of southern right whales (SRWs). Southern right whale group composition was categorized into mother–calf pairs (MC), solitary individuals (SI), breeding groups (BG), and non-social groups (NS). The latter category refers to associations of more than one whale, encompassing all age classes and sexes, without an identifiable social function (e.g., MC pairs associated with solitary individuals), modified from [ 25 ]. Drone footage of orcas harassing SRWs allowed classification of whale reactions, which are described in the Results. We also quantified the frequency of each reaction type according to the orca’s approach direction: latero-frontal and latero-caudal (Fig. 5 ). A Chi-squared test was performed to assess the independence between reaction type and approach direction [ 26 ]. The start time of the first drone clip (11:39) was used as a temporal reference for all subsequent events. When necessary, time lapses between successive events were also indicated. Finally, official orca photo-identification catalogs available online [ 27 , 28 ] were reviewed to confirm the identity and lineage of all orcas recorded in the footage. Declarations Competing interests The authors declare that they have no competing interests. Funding The Authors received NO FUNDING for this work. Author Contribution VMT, MCM, and MAC conceptualized the study. VMT and CTF curated and analyzed the data. VMT and KZ collected data and created visual aids. VMT, MCM, and CTF wrote the original draft. MAC performed statistical analysis. All the authors reviewed and edited the original draft and approved the final manuscript. Acknowledgement We thank the Programa de Monitoreo Sanitario Ballena Franca Austral members: Santiago Fernández, Silvana Aguilar, Matías Di Martino, Juan Marcos Ricciardi, Victor Fratto, Pablo De Diego, R.E.T. Vanstreels, and Marcela Uhart. We also thank Milena Fracchia for the illustrations, and Maria Cabrera (Natural Protected Area El Doradillo park ranger). This study was conducted under permits 07/2024 - DFyFS -MP and 49/2025 - SsCyAP - MTyAP of Chubut Province. 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Marine Mammals: Adaptations for an aquatic life (Springer International Publishing, 2019). Deecke, V. B., Ford, J. K. B. & Slater, P. J. B. The vocal behavior of mammal-eating killer whales: communicating with costly calls. Anim. Behav. 69 , 395–405 (2005). Baird, R. W. & Stacey, P. J. Observations on the reactions of sea lions, Zalophus californianus and Eumetopias jubatus , to killer whales, Orcinus orca : evidence of prey having a search image for predators. Can. Field-Nat . 103 , 426–428 (1989). Ljungblad, D. K. & Moore, S. E. Killer whales ( Orcinus orca ) chasing gray whales ( Eschrichtius robustus ) in the northern Bering Sea. Arctic 36 , 361–364 (1983). Best, P. B., Canham, P. A. S. & MacLeod, N. Patterns of reproduction in sperm whales, Physeter macrocephalus . Rep. Int. Whal. Comm. (Spec Issue) . 6 , 51–79 (1984). Whitehead, H. & Glass, C. Orcas (killer whales) attack humpback whales. J. Mammal . 66 , 183–185 (1985). Arnbom, T., Papastavrou, V., Weilgart, L. S. & Whitehead, H. Sperm whales react to an attack by killer whales. J. Mammal . 68 , 450–453 (1987). Campagna, C. et al. Catastrophic mortality of southern elephant seals caused by H5N1 avian influenza. Mar. Mamm. Sci. 40 , 322–325 (2024). Rimondi, A. et al. Highly pathogenic avian influenza A (H5N1) viruses from multispecies outbreak, Argentina, August 2023. Emerg. Infect. Dis. 30 , 812–814 (2024). Estes, J. A. et al. Complex trophic interactions in kelp forest ecosystems. Bull. Mar. Sci. 74 , 621–638 (2004). Estes, J. A., Doak, D. F., Springer, A. M. & Williams, T. M. Causes and consequences of marine mammal population declines in southwest Alaska: a food-web perspective. Phil Trans. R Soc. B . 364 , 1647–1658 (2009). Additional Declarations No competing interests reported. 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05:24:10","extension":"xml","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":99568,"visible":true,"origin":"","legend":"","description":"","filename":"b5c2981540d94fd69cf2fb21347b2c7e1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/72998db0491696ac333637a5.xml"},{"id":95264336,"identity":"3b9b02b2-be0b-4c0f-b246-e0886c11a67b","added_by":"auto","created_at":"2025-11-06 05:24:09","extension":"html","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":108974,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/86e36479fa2d963357ca77dc.html"},{"id":95264352,"identity":"98e79d21-0e20-4bf8-a1c5-c90e988f40fa","added_by":"auto","created_at":"2025-11-06 05:24:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":884192,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of the vantage points in the Natural Protected Area El Doradillo (Chubut, Argentina; see Methods), showing drone flight tracks (color lines) and their starting local times (UTC-3). Isobaths of 5, 10, 15, 25 and 30 m are included.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/38b28dbba99550dcc8579b07.png"},{"id":95264339,"identity":"1fc953cd-35b5-4e37-bfd6-3e7a65fbe181","added_by":"auto","created_at":"2025-11-06 05:24:09","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":386678,"visible":true,"origin":"","legend":"\u003cp\u003eOrca group engaged in prey-handling and harassment of southern right whales.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/a29b36fc1fcf127cdc71d0fb.png"},{"id":95264294,"identity":"81a96a41-4694-40ad-bb07-c90bf2f0cd75","added_by":"auto","created_at":"2025-11-06 05:24:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":709072,"visible":true,"origin":"","legend":"\u003cp\u003ePhotograms from drone footage showing the sequence of prey handling and cooperative feeding by orcas. a) Jazmín’s calf surfacing with a piece of flesh near its mother; b) Carcass showing missing fluke tips and bite marks; c) Carcass showing an open lateroventral wound exposing blood and blubber; d) One of the orcas holding the carcass by the pectoral fin; e) The calf surfacing with a piece of skin and blubber and other orcas sharing prey; f) Larger individuals maintaining the carcass near the surface by holding strips of peeling skin; g) Orcas removing skin from the carcass; h) Three orcas feeding at the same time; i) Jazmín sharing prey with her calf; j) One orca holding the carcass while another inspects its mouth; k) Carcass completely stripped of skin from the posterior head region to the tailstock; and l) Orca feeding on carcass internal organs.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/1cdfbcc7bb1288ce2d73bb35.png"},{"id":95264346,"identity":"4747262b-5097-4027-9212-dbaa06a3b672","added_by":"auto","created_at":"2025-11-06 05:24:09","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":131430,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of whale reactions to approaching orcas: (a) “360° turn” and (b) “zigzag pattern.” Arrows represent the temporal progression of movements, not spatial trajectory. Illustrations by Milena Fracchia.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/c795d86431bf8ab3d4063192.png"},{"id":95264330,"identity":"477395a1-a378-419c-b783-5581d1c5e33a","added_by":"auto","created_at":"2025-11-06 05:24:09","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":60840,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of the two approach directions of orcas toward whales during observed harassment events. Illustration by Milena Fracchia.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/2b9c1936cf4f33e41fa4b2d5.png"},{"id":98627909,"identity":"af9687db-e139-4640-98b0-bbdd66716d1a","added_by":"auto","created_at":"2025-12-19 17:10:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2763173,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7880511/v1/93b6369a-ddeb-4566-bc74-9eb9e82e1b1e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Orca (Orcinus orca) prey-handling and harassment of southern right whales (Eubalaena australis) in Península Valdés, Argentina","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe orca (\u003cem\u003eOrcinus orca\u003c/em\u003e), or killer whale, is the largest extant dolphin and a top predator in all ocean basins [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Although considered a generalist predator, different populations exhibit specific prey preferences and hunting strategies, often associated with acoustic repertoires and morphological characteristics, leading to the differentiation of several ecotypes worldwide [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. These ecotypes are commonly classified as fish- or marine mammal-eaters, though the distinction is not absolute, as fish-eating populations are known to prey on marine mammals and vice versa [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Globally, orcas prey on at least eighteen species of cetaceans, including the largest baleen whale, \u003cem\u003eBalaenoptera musculus\u003c/em\u003e [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOrca predation on baleen whales (Mysticetes) occurs across multiple oceans, including the North Pacific, South Pacific, Indian, and Southern Oceans [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], and is thought to influence prey abundance, distribution, behavior, and evolution [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. For example, orcas significantly affect gray whale (\u003cem\u003eEschrichtius robustus\u003c/em\u003e) calf survival and migration patterns [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Similarly, bowhead whales (\u003cem\u003eBalaena mysticetus\u003c/em\u003e) exhibit pronounced and prolonged behavioral responses to orca predation risk, which may reduce their fitness and indicate ecological impacts beyond direct mortality [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eWhile orca predation on baleen whales is globally recognized, its occurrence in the South Atlantic Ocean, particularly along the Argentine coast, remains poorly documented. The orca population of Pen\u0026iacute;nsula Vald\u0026eacute;s (Chubut, Argentina) is best known for its unique foraging strategy of intentionally stranding on beaches to capture South American sea lions (\u003cem\u003eOtaria flavescens\u003c/em\u003e) and South American elephant seal (\u003cem\u003eMirounga leonina\u003c/em\u003e) pups, a culturally transmitted technique passed across generations [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Although pinnipeds are their main prey, orcas in this region also consume sharks, rays and possibly tuna [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]; as well as dusky dolphins (\u003cem\u003eAethalodelphis obscurus;\u003c/em\u003e [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eRegarding this orca population, previous opportunistic observations of predation events on baleen whales have been reported. In Pen\u0026iacute;nsula Vald\u0026eacute;s, a confirmed attack occurred in 1971 [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and numerous interactions were later reported [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Between 1972 and 2000, 117 encounters between orcas and SRWs were documented, 12 of which were classified as attacks, characterized by intense activity from both species, bite marks on the whales, and visible blood or blubber pieces at the surface [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Globally, similar attacks on SRW calves have been documented in southern Brazil [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] and other regions [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePen\u0026iacute;nsula Vald\u0026eacute;s is a critical area for both SRW and orcas. It serves as a major breeding and calving ground for SRWs, which aggregate in the sheltered Nuevo and San Jos\u0026eacute; gulfs and adjacent coastal areas from late autumn to late spring (May-December) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Orcas, by contrast, occur year-round but are more frequently observed outside the gulfs, particularly at Punta Norte and Caleta Vald\u0026eacute;s, during late austral spring and summer, coinciding with the reproductive season of their main prey [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Nonetheless, orcas occasionally enter the gulfs, where their presence overlaps spatiotemporally with that of SRW, increasing the likelihood of predator-prey interactions.\u003c/p\u003e\u003cp\u003eDespite the ecological significance of orca predation on baleen whales, our understanding of this phenomenon in Argentina remains limited. In particular, little is known about how orcas in this region handle, feed on, and share cetacean carcasses. Here, we combine shore-based observations with drone footage to provide the first detailed description of orca prey-handling and feeding behavior following the hunting of a SRW calf, alongside repeated harassment events, and the whale\u0026rsquo;s behavioral responses near Pen\u0026iacute;nsula Vald\u0026eacute;s.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe orca group was first sighted at 11:20 local time (UTC-3), when dorsal fins were observed through binoculars breaking the sea surface approximately 2 km offshore from our vantage point, Punta Ameghino cliff (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A drone was launched at 11:33, arriving to the area shortly after and confirming the presence of six orcas (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The group comprised \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e (PTN-002, female, born in 1991), her recent calf (unnamed, believed to be male, first sighted in June 2024), and two older offspring, \u003cem\u003eAuka\u003c/em\u003e (PTN-029, sex unknown, born in 2016) and \u003cem\u003eMorgan\u003c/em\u003e (PTN-036, sex unknown, born in 2002), as well as \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e\u0026rsquo;s sister, \u003cem\u003eLlen\u003c/em\u003e (PTN-010, female, born in 2000) and her daughter, \u003cem\u003eShotel\u003c/em\u003e (PTN-026, female, born in 2014).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eWhen the drone reached the group (11:39), no southern right whales (SRWs) were detected within a 500 m radius. The orcas were actively performing short vertical dives and subsurface circling in a restricted area, without any evidence of feeding behavior. After almost ten minutes (11:48), \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e\u0026rsquo;s calf surfaced carrying a small, red-colored piece of flesh in its mouth (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). The group continued performing short dives for approximately eight minutes, until \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e refloated a SRW calf carcass (11:56) from an estimated depth of 10 m (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The orcas were thus feeding on a sunken whale calf.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eCooperative prey-handling and feeding behavior\u003c/h2\u003e\u003cp\u003eUpon bringing the carcass to the surface, \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e maintained its grip by holding a torn piece of skin, preventing it from sinking. The other group members gathered around, actively biting off pieces of tissue. The carcass appeared fresh and well preserved; both fluke tips were missing and bore clear bite marks, while the head and pectoral fins remained intact (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, c). The carcass was open on the lateroventral side, exposing blood and blubber (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e\u003cp\u003eFrom the moment the carcass was refloated and throughout the main event (total duration 1 h 29 min), the orcas maintained a relatively stationary position, refloating and allowing the carcass to sink twice. No adult or calf SRWs were observed nearby, and those within a radius of 500 m, did not show evidence of disturbance. The orcas appeared to coordinate their actions, apparently, taking turns to keep the carcass at or near the surface. Larger individuals held the carcass by strips of peeling skin or by the pectoral fin, while others positioned themselves underneath to lift it (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). At times, individuals were observed intentionally pushing the carcass to greater depths and allowing it to sink. After approximately two minutes of such behavior, they released the carcass and resumed short vertical dives, surfacing with pieces of tissue in their mouths (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). A second refloating event occurred at 12:06, during which the orcas continued removing skin in the upper few meters of the water column (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef).\u003c/p\u003e\u003cp\u003eFor the next 41 minutes, orcas repeatedly surfaced with strips of skin in their mouths, peeled the carcass, and shared prey (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg, h). \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e remained closely associated with her calf, who occasionally swam alone or with \u003cem\u003eMorgan\u003c/em\u003e. While swimming in parallel, the calf repeatedly attempted to obtain pieces of prey directly from its mother\u0026rsquo;s mouth and occasionally from \u003cem\u003eMorgan\u003c/em\u003e\u0026rsquo;s (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ei). At one point, one orca held the carcass below the surface while another was observed inspecting the carcass\u0026rsquo; mouth, placing its head inside it (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ej). By 12:47, \u003cem\u003eShotel\u003c/em\u003e was manipulating the prey alone until it detached a piece of skin and swam away, leaving the carcass to the other. For approximately 30 min thereafter, only five orcas interacted with the carcass while one individual remained out of sight. During this time, the carcass was completely stripped of skin from the posterior head region to the tailstock (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ek), and the orcas were seen feeding and sharing internal organs (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003el).\u003c/p\u003e\u003cp\u003eAt 13:18, the orcas began moving northward along the coast, leaving the carcass behind. The final observation of feeding occurred at 13:28, when \u003cem\u003eJazm\u0026iacute;n\u003c/em\u003e and her calf were seen carrying and sharing an organ. By that time, the group was approximately 2 km from the carcass, marking the end of the main prey-handling event at 14:01.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eHarassment and whale responses\u003c/h3\u003e\n\u003cp\u003eBetween 14:15 and 15:51, a total of 46 orca harassment events directed towards 90 SRWs were recorded. Of these events, 34 elicited active reactions from whales (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Two main reaction types were identified: a \u0026ldquo;360\u0026deg; turn\u0026rdquo; and a \u0026ldquo;zigzag pattern\u0026rdquo; (see description below; Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, b). Most harassment events targeted mother-calf (MC) pairs (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), and although all six orcas participated, one individual separated carried out most approaches alone. In 35 of the 46 events, no physical contact occurred. The whales showed no anticipatory response to the orcas\u0026rsquo; approach in any of the 46 harassment events.\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\u003eTotal number of harassment events categorized by whale reaction type and group composition. BG: breeding groups; MC: mother\u0026ndash;calf pairs, NS: non-social groups; SI: solitary individuals; No: No reaction.\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\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eReaction\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroup composition\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e360\u0026deg; turn\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eZigzag\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\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\u003e7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBG\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\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\u003e1\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\u003e23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e46\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 \u0026ldquo;360\u0026deg; turn\u0026rdquo; reaction involved a 360\u0026deg; full body turn of the whale upon close approach or physical contact by the orcas (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). This movement occurred in the horizontal plane, rather than as a roll along the whale\u0026rsquo;s longitudinal axis and was observed in all group categories except breeding groups (BG) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Among MC pairs, the mother\u0026rsquo;s responses were immediate, turning rapidly and positioning their calves inside the circle. In a few cases, calves positioned themselves either on top of the mother\u0026rsquo;s back or outside the circle. The \u0026ldquo;zigzag pattern\u0026rdquo; reaction consisted of a strong lateral undulation of the body, resembling a snake-like motion, with the body forming an \u0026ldquo;S\u0026rdquo; shape (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). These movements involved vigorous tail swings, occasionally producing tail slaps. Although less frequent, this reaction was observed in all group categories except BG (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eMost harassment events involved a latero-caudal approach (N\u0026thinsp;=\u0026thinsp;28) rather than latero-frontal (N\u0026thinsp;=\u0026thinsp;6) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The whale\u0026rsquo;s behavioral response was not independent of the direction from which the orcas approached. Considering both directions and both responses (360\u0026deg; turn and zigzag), whales reacted differently. Orcas were prone to approach from the latero-caudal direction and elicited a 360\u0026deg; turn more often than expected by chance (Chi-squared test, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.008), whereas both responses were equally probable when the approach was latero-frontal.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn twelve cases, no whale behavioral response was observed (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These included one BG (1 Female\u0026thinsp;+\u0026thinsp;2 Males), three non-social groups (NS; 1 MC pair\u0026thinsp;+\u0026thinsp;1 adult; 2 adults; and 3 adults), one solitary individual (SI), and seven MC pairs. Orca approaches occurred from both directions: nine latero-caudal, and three latero-frontal. Despite close proximity, no physical contact was observed between the species.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis report provides the first video-documented evidence of orca prey-handling and feeding on a southern right whale (SRW) in the Southwestern Atlantic Ocean. It also documents multiple harassment events carried out by the same group in a single day, along with the defensive responses by SRWs. Together, these observations provide new insights into orca predatory behavior and whale defense strategies in Patagonia. The feeding event we report involved a SRW calf, consistent with previous observations of orca predation on large cetaceans [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSix identified orcas were observed feeding on a sunken SRW calf carcass, which they repeatedly refloated to the surface. Although the hunting was not witnessed, the carcass appeared fresh and well-preserved, suggesting that the calf had been killed probably hours before our arrival. According to park rangers from the protected area, the group had been observed nearshore earlier that morning, disappearing shortly afterwards (Maria Cabrera, pers. comm.). Several characteristics of the carcass suggest prior orca predation. Both fluke tips were missing and bore clear bite marks, implying that orcas disabled the whale's primary propulsion organ, the tail, thus reducing its capacity to perform defensive tail slaps or escape through rapid swimming. The fluke\u0026rsquo;s soft, boneless tissue also makes it easier to bite than the bony pectoral fins, which were intact. Similar selective feeding on accessible, soft tissue, especially tongues, has been reported in other cetacean prey [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. While one individual was seen inserting its snout into the carcass\u0026rsquo;s mouth, no direct evidence of tongue consumption was found.\u003c/p\u003e\u003cp\u003eOrca predation on cetaceans is often constrained by the rapid sinking of carcasses into waters deeper than 400 m, therefore limiting consumption to soft tissues such as the tongue and lips due to inaccessibility (e.g., [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]). In contrast, the event reported here occurred in shallow waters (~\u0026thinsp;10 m), allowing prolonged access and extensive exploitation of the carcass, including skin, blubber, muscles, and internal organs. Similar behavior has been described in mammal-eating transient orcas in the Northeastern Pacific Ocean, where food-storing behavior and prolonged feeding on grey whale calves' sunken carcasses occurred in shallow waters (between 15 and 75 m deep; [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]).\u003c/p\u003e\u003cp\u003eCooperative prey-handling was evident throughout the event. Larger individuals coordinated efforts to keep the carcass near the surface, alternatively gripping strips of skin or lifting it from below. Instances of prey-sharing were also recorded, including mouth-to-mouth transfers, a behavior previously described for this species [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. These observations highlight both the social complexity and cooperative strategies involved in orca prey use [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Moreover, the prey-sharing behavior observed here between the youngest calf, its mother and sibling likely plays a role in the learning process of communal hunting, as described in other populations [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Additionally, this observation suggests that calves in this population may begin supplementing milk with solid food early in life, reflecting a transitional or mixed diet similar to that of orcas from the Northeastern Pacific Ocean [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe harassment events occurred within a SRW nursery area and were primarily directed at mother-calf (MC) pairs. These groups are both the most abundant and the most vulnerable in the area due to calves\u0026rsquo; small size and limited diving capacity [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. The 360\u0026deg; turn response observed in mothers appears to be a defensive maneuver positioning the calves at the center of a protective circle, thus reducing orca access. In contrast, the zigzag response, involving vigorous lateral tail movements, may act as an active deterrent, with potential to strike or stun approaching orcas [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eMost orca approaches were latero-caudal, effectively exploiting the whales\u0026rsquo; reduced visual field and blind spots (i.e., located along the body\u0026rsquo;s longitudinal axis, directly anterior and posterior to the body). Mysticetes have laterally positioned eyes, each providing a\u0026thinsp;~\u0026thinsp;130\u0026deg; panoramic view, but independent ocular movement and optic nerve anatomy, along with their large heads, limit binocular vision and create a blind zone directly ahead [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Thus, defensive strategies such as lateral undulations or 360\u0026deg; rotations may help whales bring predators into view. Additionally, the absence of whales\u0026rsquo; anticipatory responses suggests that the orcas were acoustically silent during the harassment events, consistent with the behavior of mammal-eating transient orcas, which are generally silent while foraging [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. This indicates that whales may rely primarily on vision, rather than hearing, to detect and avoid such predators [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAlthough grouping during orca attacks has been observed in large whales [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e] and collective defense, such as the \u0026ldquo;rosette\u0026rdquo; or \u0026ldquo;marguerite\u0026rdquo; formation, has been previously described for SRWs [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], they were not observed in this study. This may reflect the short duration of harassment events and their failure to escalate into full predatory attempts. In this context, the multiple harassments of SRW may represent exploratory or training behavior. As they occurred after the main feeding event, harassment may not have been motivated by foraging but rather associated with orca social learning or practice. This is consistent with the well-documented intentional stranding behavior in this population, a culturally transmitted practice through which juveniles acquire skills by observing and participating [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn the events reported here, the orcas were observed spending most of their time in waters shallower than 10 m. In some regions, whales may use shallow waters as a refuge from orca attacks, as these restrict the directions of attack and pose a stranding risk for orcas [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. This strategy has been proposed as a defense for SRWs in Pen\u0026iacute;nsula Vald\u0026eacute;s [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, we suggest that this would not be a successful strategy against attacks from this particular orca population, as they regularly operate in very shallow waters when intentionally beaching to capture pinnipeds [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Therefore, the shallow environment would not constrain the orcas, instead it may increase stranding risk and reduce the range of defensive options for SRWs in this area.\u003c/p\u003e\u003cp\u003eEcological conditions may have influenced the observed behaviors. The 2023 outbreak of a highly pathogenic avian influenza (HPAI H5N1) caused severe mortality in the South American elephant seal population, killing\u0026thinsp;~\u0026thinsp;97% of newborn pups and significantly reducing adult numbers [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Population size has since declined by 60%. South American sea lion colonies at Pen\u0026iacute;nsula Vald\u0026eacute;s were also heavily affected [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. By contrast, on August 19, 2025 SRW aerial census recorded a historic peak of 2,110 individuals, including 826 newborns (LAMAMA, unpublished data). This imbalance in prey availability may have encouraged orcas to harass and exploit whales more frequently. Stable isotope analyses from this orca population support such dietary flexibility, showing structuring consistent with seasonal prey fluctuations and individual dietary preferences [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe observations presented here reinforce the ecological significance of orcas as apex predators in northern Patagonia, capable of rapidly adapting their foraging strategies to changing prey landscapes. From early August to mid-October 2025, at least two other predation events on SRW calves were directly observed, while one additional stranded carcass bore confirmed signs of orca predation and three showed evidence of potential orca predation (Programa de monitoreo sanitario Ballena Franca Austral, PMSBFA pers. comm.). Therefore, the number of calves killed by orcas would rise to at least seven. Although likely an underestimate, these events suggest an increasing interaction frequency between orcas and SRWs.\u003c/p\u003e\u003cp\u003eIf such events become more common, it could affect SRW calf survival, distribution, and behavior, with potential demographic consequences. As top predators, orcas can exert cascading effects in marine ecosystems [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Continuous monitoring of orca\u0026ndash;SRW interactions will be essential for understanding these predator-prey dynamics and their implications for the SRW population in the region.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eThis report is based on shore-based observations conducted on September 5, 2025, within the Natural Protected Area El Doradillo (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The orca group was first detected using binoculars from Punta Ameghino cliff, 20 m above sea level. Continuous visual monitoring began at 11:20 local time (UTC-3) and continued until 16:00 supplemented by drone footage. By the end of the observation period, our position had shifted to Punta Prism\u0026aacute;tico cliff, 25 m above sea level (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Drone flight tracks documented the orca\u0026rsquo;s movements along the coast throughout the observation period (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eDrone footage was obtained using a DJI Mavic 4, 6K 28mm \u0026amp; 4K 70mm equivalent cameras, operated under calm wind conditions. Due to drone battery and memory card limitations, uninterrupted recording was not possible. Consequently, behavioral descriptions were derived from both drone footage (total recording time: 1 h 37 min) and direct visual observations made by the authors.\u003c/p\u003e\u003cp\u003eVideo footage was analyzed independently by two of the authors (V.M.T. and E.C.T.F.). Orca behavior was assessed using the focal group follow protocol with \u003cem\u003ead libitum\u003c/em\u003e event recording [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Analyses focused on prey-handling and harassment behaviors, as well as the reactions and defensive responses of southern right whales (SRWs).\u003c/p\u003e\u003cp\u003eSouthern right whale group composition was categorized into mother\u0026ndash;calf pairs (MC), solitary individuals (SI), breeding groups (BG), and non-social groups (NS). The latter category refers to associations of more than one whale, encompassing all age classes and sexes, without an identifiable social function (e.g., MC pairs associated with solitary individuals), modified from [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Drone footage of orcas harassing SRWs allowed classification of whale reactions, which are described in the Results. We also quantified the frequency of each reaction type according to the orca\u0026rsquo;s approach direction: latero-frontal and latero-caudal (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). A Chi-squared test was performed to assess the independence between reaction type and approach direction [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe start time of the first drone clip (11:39) was used as a temporal reference for all subsequent events. When necessary, time lapses between successive events were also indicated. Finally, official orca photo-identification catalogs available online [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] were reviewed to confirm the identity and lineage of all orcas recorded in the footage.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eCompeting interests\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThe Authors received \u003cb\u003eNO FUNDING\u003c/b\u003e for this work.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eVMT, MCM, and MAC conceptualized the study. VMT and CTF curated and analyzed the data. VMT and KZ collected data and created visual aids. VMT, MCM, and CTF wrote the original draft. MAC performed statistical analysis. All the authors reviewed and edited the original draft and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe thank the Programa de Monitoreo Sanitario Ballena Franca Austral members: Santiago Fern\u0026aacute;ndez, Silvana Aguilar, Mat\u0026iacute;as Di Martino, Juan Marcos Ricciardi, Victor Fratto, Pablo De Diego, R.E.T. Vanstreels, and Marcela Uhart. We also thank Milena Fracchia for the illustrations, and Maria Cabrera (Natural Protected Area El Doradillo park ranger). This study was conducted under permits 07/2024 - DFyFS -MP and 49/2025 - SsCyAP - MTyAP of Chubut Province.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data supporting the findings of this study are available from the corresponding author upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFord, K. B. Killer whale: \u003cem\u003eOrcinus orca\u003c/em\u003e. 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B\u003c/em\u003e. \u003cb\u003e364\u003c/b\u003e, 1647\u0026ndash;1658 (2009).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":true,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Killer whale, harassment, cooperative feeding, predator-prey interactions, behavioral responses, drone footage","lastPublishedDoi":"10.21203/rs.3.rs-7880511/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7880511/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWe report the first video-documented case of orca (\u003cem\u003eOrcinus orca\u003c/em\u003e) cooperative prey-handling and feeding behavior on a southern right whale (SRW, \u003cem\u003eEubalaena australis\u003c/em\u003e) calf carcass, along with harassment events and whale responses, recorded in the Natural Protected Area El Doradillo in Pen\u0026iacute;nsula Vald\u0026eacute;s, Argentina. Drone footage and shore-based observations were conducted on September 5, 2025, revealing an orca group refloating and feeding on a sunken whale calf carcass. The orca group consisted of six identified individuals from the Pen\u0026iacute;nsula Vald\u0026eacute;s population. Drone footage (total recording time: 1 h 37 min) showed coordinated behavior among orcas, who alternated in holding, lifting, and releasing the carcass, suggesting cooperative handling. The orcas engaged in forty-six harassment events targeting southern right whales, especially mother\u0026ndash;calf pairs. Defensive responses described as 360\u0026deg; turns and zigzag pattern were elicited more often when orcas approached from the latero-caudal angle with respect to SRW head. These results expand the knowledge on the behavioral ecology of this orca population and underscore the ecological significance of orca\u0026ndash;right whale interactions in one of the most important SRW breeding grounds in the Southwestern Atlantic Ocean.\u003c/p\u003e","manuscriptTitle":"Orca (Orcinus orca) prey-handling and harassment of southern right whales (Eubalaena australis) in Península Valdés, Argentina","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-06 05:23:49","doi":"10.21203/rs.3.rs-7880511/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e71d5d4e-741d-473d-a02d-6c507eca146d","owner":[],"postedDate":"November 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57345936,"name":"Biological sciences/Ecology"},{"id":57345937,"name":"Earth and environmental sciences/Ecology"},{"id":57345938,"name":"Biological sciences/Zoology"}],"tags":[],"updatedAt":"2025-12-19T04:38:30+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-06 05:23:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7880511","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7880511","identity":"rs-7880511","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}