Short-finned Pilot Research Articles

Pairing AIS data and underwater topography to assess maritime traffic pressures on cetaceans: Case study in the Guadeloupean waters of the Agoa sanctuary

Maritime transportation forecasts project an increase in shipping. In this context, interactions with cetaceans are of growing concern especially when relevant biological data are not available to monitor the impacts. The Agoa sanctuary in the Wider Caribbean region faces this situation. To overcome this issue, we used AIS data to estimate three pressure types from maritime traffic associated with known impacts for cetaceans: (1) “intensity” corresponding to the frequency of vessel presence, (2) “occupancy” corresponding to the duration of ship presence, known to lead to disturbance and noise-related impacts and (3) “speed” presenting the risk of physical injuries from collisions. A simplified approach of the Cumulative Effect Assessment framework was used. We mapped species underwater topographic preferences as a proxy for their distribution to link habitat features with traffic pressure maps to evaluate pressure levels and types. Results showed that three species were more at risk from intensity and speed in the plains: the bottlenose dolphins, the Fraser’s dolphins and the short-finned pilot whales. The speed pressure had the highest score over the habitat types slopes, canyons and valleys, placing sperm whales, Cuvier, Blainville’s and Gervais’s beaked whales at higher risk of collision in these areas. Humpback whales and pantropical spotted dolphins faced a higher risk of disturbance over the continental shelf along the West coast. We recommend a precautionary approach in the Agoa sanctuary: speed reduction in the Pointe-à-Pitre-Marie-Galante route and displacement of shipping lanes to move maritime traffic away from the West Coast.

Discriminating and classifying odontocete echolocation clicks in the Hawaiian Islands using machine learning methods.

Passive acoustic monitoring (PAM) has proven a powerful tool for the study of marine mammals, allowing for documentation of biologically relevant factors such as movement patterns or animal behaviors while remaining largely non-invasive and cost effective. From 2008–2019, a set of PAM recordings covering the frequency band of most toothed whale (odontocete) echolocation clicks were collected at sites off the islands of Hawaiʻi, Kauaʻi, and Pearl and Hermes Reef. However, due to the size of this dataset and the complexity of species-level acoustic classification, multi-year, multi-species analyses had not yet been completed. This study shows how a machine learning toolkit can effectively mitigate this problem by detecting and classifying echolocation clicks using a combination of unsupervised clustering methods and human-mediated analyses. Using these methods, it was possible to distill ten unique echolocation click ‘types’ attributable to regional odontocetes at the genus or species level. In one case, auxiliary sightings and recordings were used to attribute a new click type to the rough-toothed dolphin, Steno bredanensis. Types defined by clustering were then used as input classes in a neural-network based classifier, which was trained, tested, and evaluated on 5-minute binned data segments. Network precision was variable, with lower precision occurring most notably for false killer whales, Pseudorca crassidens, across all sites (35–76%). However, accuracy and recall were high (>96% and >75%, respectively) in all cases except for one type of short-finned pilot whale, Globicephala macrorhynchus, call class at Kauaʻi and Pearl and Hermes Reef (recall >66%). These results emphasize the utility of machine learning in analysis of large PAM datasets. The classifier and timeseries developed here will facilitate further analyses of spatiotemporal patterns of included toothed whales. Broader application of these methods may improve the efficiency of global multi-species PAM data processing for echolocation clicks, which is needed as these datasets continue to grow.

How evolutionary biology can explain why human and a few marine mammal females are the only ones that are menopausal

Two fundamental questions related to menopause that have not been answered are: (1) why does menopause even occur? And, (2) of the more than six thousand known mammals extant today, why human and four whale females are the only ones that are menopausal? Answers to both of these basic questions are provided here on the basis of evolutionary biology. From observational data, it was found that there are three elemental criteria that all menopausal species must fulfill: first, it has to be long-lived (average female lifespan of the species has to be forty years or more); second, it must live in groups; and third, the average female-male lifespan differential has to be at least thirty percent or more. In addition, a corollary criterion for menopause was also established: for a species’ females to be menopausal, the Encephalization Quotient (EQ) for the species has to be 2.5 or more. Though humans do not fulfill the third menopausal criterion currently, it has been shown that when the menopausal mechanism first became common in human ancestors, in all likelihood, that principle was conformed to. Of the multitude of mammals around, only a few species satisfy all three menopausal criteria, and hence are the only ones whose females undergo the menopausal process. Many hitherto unanswered questions with respect to menopause, such as, while long and short-finned pilot whales are close to each other both genetically and physiologically, why short-finned females are menopausal while long-finned females are not, why orca females are menopausal while elephant females are not, in spite of both being long-lived, etc., can be answered on the basis of those three criteria. Why there was no selection pressure for males to undergo advanced-age reproductive cessation in those few menopausal species and why the majority of divorces occur in mid-life (40-to-60s) are also explained from a menopausal perspective.

Identification of western North Atlantic odontocete echolocation click types using machine learning and spatiotemporal correlates.

A combination of machine learning and expert analyst review was used to detect odontocete echolocation clicks, identify dominant click types, and classify clicks in 32 years of acoustic data collected at 11 autonomous monitoring sites in the western North Atlantic between 2016 and 2019. Previously-described click types for eight known odontocete species or genera were identified in this data set: Blainville’s beaked whales (Mesoplodon densirostris), Cuvier’s beaked whales (Ziphius cavirostris), Gervais’ beaked whales (Mesoplodon europaeus), Sowerby’s beaked whales (Mesoplodon bidens), and True’s beaked whales (Mesoplodon mirus), Kogia spp., Risso’s dolphin (Grampus griseus), and sperm whales (Physeter macrocephalus). Six novel delphinid echolocation click types were identified and named according to their median peak frequencies. Consideration of the spatiotemporal distribution of these unidentified click types, and comparison to historical sighting data, enabled assignment of the probable species identity to three of the six types, and group identity to a fourth type. UD36, UD26, and UD28 were attributed to Risso’s dolphin (G. griseus), short-finned pilot whale (G. macrorhynchus), and short-beaked common dolphin (D. delphis), respectively, based on similar regional distributions and seasonal presence patterns. UD19 was attributed to one or more species in the subfamily Globicephalinae based on spectral content and signal timing. UD47 and UD38 represent distinct types for which no clear spatiotemporal match was apparent. This approach leveraged the power of big acoustic and big visual data to add to the catalog of known species-specific acoustic signals and yield new inferences about odontocete spatiotemporal distribution patterns. The tools and call types described here can be used for efficient analysis of other existing and future passive acoustic data sets from this region.

Short-finned pilot whales exhibit behavioral plasticity in foraging strategies mediated by their environment

Predators adapt their foraging behavior to exploit a variety of prey in a range of environments. Short-finned pilot whales are wide-ranging predators in tropical and sub-tropical oceans, but most previous studies of their foraging ecology have been conducted near oceanic islands. We deployed sound- and movement-recording tags on 43 short-finned pilot whales off Cape Hatteras, North Carolina, USA, to measure their foraging behavior in a continental shelf-break ecosystem and investigate how variation in the environment shapes their behavior. Overall, the foraging behavior of pilot whales off Cape Hatteras was similar to that of their counterparts from island-associated habitats. Off Cape Hatteras, pilot whales made foraging dives as deep as 1077 m (mean: 445 m), lasting up to 23 min (mean: 12.8 min), with sprints (pursuit at speeds over 3 m s-1and up to 6.9 m s-1) in more than half of foraging dives. However, tagged whales off Cape Hatteras produced higher buzz rates (11.3 buzzes dive-1), foraged more extensively in daytime hours, and engaged in more frequent benthic foraging than island-associated ecotypes. By parsing the echoic scene generated by the animal’s own echolocation clicks, we show that pilot whales off Cape Hatteras frequently exploit bathymetric features for foraging, with benthic dives resulting in higher prey capture attempts than pelagic dives. The ability of these predators to strategically adapt foraging strategies to local habitat features likely contributes to their ecological success and may allow them to adjust to shifts in prey distributions in a rapidly changing Anthropocene ocean.

First recorded stranding of a short-finned pilot whale, Globicephala macrorhynchus, in Britain.

A male pilot whale, Globicephala sp., was reported as a live stranding on 1st March 2012 at Hazelbeach, near Neyland, Pembrokeshire. It was euthanased and its skull was recovered during an onsite necropsy. Examination of the skull and contemporary photographs of the stranded animal confirm that this is the first record of short-finned pilot whale, Globicephala macrorhynchus, in Britain.

Shark species identification from bite marks on a Short-finned Pilot Whale, Globicephala macrorhynchus

A Short-finned Pilot Whale, Globicephala macrorhynchus, was found dead and with shark bites along its body on a beach in northeast Brazil. The present study aimed to identify the shark species responsible for the bites as well as to estimate its/their total length. Species identification was performed using the bite marks, which were of the same diameter, suggesting they were infected by one or more Tiger sharks of similar size. The characteristics of the bites and the shape and distribution of the marks left by the teeth pointed to the Tiger Shark, Galeocerdo cuvier. The total length of the Tiger Shark or sharks was estimated at between 257 and 288 cm, based on the perimeter contour of each bite and the interdental distance inferred from the marks on the whale. This suggests that the bites were inflicted by one or more sub-adult specimens.

Spatial and temporal characterization of the exposure of island-associated cetacean populations to whale-watching in Madeira Island (NE Atlantic)

The whale-watching industry can represent a critical anthropogenic stressor for the targeted populations. Identifying and characterizing the individual exposure to wildlife tourism in island-associated cetacean communities is especially relevant in small, remote oceanic regions relying on tourism. This study characterized the spatial and temporal variation of the whale-watching pressure on common bottlenose dolphins (Tursiops truncatus) and short-finned pilot whales (Globicephala macrorhynchus) in Madeira Island and identified the most exposed portion of the population, making use of diverse long-term datasets (i.e. sighting data, photographic data and vessels’ tracks) obtained year-round from platforms of opportunity (whale-watching operators) and proposing a new descriptive index which estimates the cumulative exposure rates. Core areas of encounters with the whale-watching vessels were identified off the capital city of Funchal. A daily average of 6.5 (±2.2 SD) vessels were concurring in this area, with a significantly higher number recorded between May and October and a peak of 14 vessels in August. From a total of 367 identified bottlenose dolphins and 536 pilot whales, a minimum of 6% and 10%, respectively, were identified as island-associated individuals. Cumulative exposure rates for these individuals could reach levels over two times higher than the general trend for both species. A higher proportion of island-associated bottlenose dolphins were recorded in the winter season. In contrast, island-associated pilot whales were predominant (over 50%) or in a high proportion (over 40%) year-round. The present study highlights the importance of using data from platforms of opportunity to investigate anthropogenic stressors, as tourism-based cetacean observation. It also provides insights into the whale-watching pressure on island-associated individuals occurring in oceanic areas and calls attention to the need of monitoring the fitness and well-being of these wildlife populations in Madeira Archipelago, an outermost European region.

Decreased resting and nursing in short-finned pilot whales when exposed to louder petrol engine noise of a hybrid whale-watch vessel

Vessel noise is a primary driver of behavioural disturbance in cetaceans, which are targeted during whale-watch activities. Despite the growing, global effort for implementing best-practice principles, to date, there are no regulations on whale-watch vessel noise levels. Here, we test the hypothesis that a whale-watch vessel with a low noise emission will not elicit short-term behavioural responses in toothed whales compared to a vessel with a louder engine. We measured behavioural responses (n = 36) of short-finned pilot whales (Globicephala macrorhynchus) to whale-watch vessel approaches (range 60 m, speed 1.5 kn). Treatment approaches with a quieter electric engine (136–140 dB) compared to the same vessel with a louder petrol engine (151–139 dB) (low-frequency–mid-frequency weighted source levels, re 1 µPa RMS @ 1 m) were examined. Focal whales were resting mother and calves in small group sizes. During petrol engine treatments, the mother’s mean resting time decreased by 29% compared to the control (GLM, p = 0.009). The mean proportion of time nursing for the calf was significantly influenced by petrol engine vessel passes, with a 81% decrease compared to the control (GLM, p = 0.01). There were no significant effects on behaviour from the quieter electric engine. Thus, to minimise disturbance on the activity budget of pilot whales, whale-watch vessels would ideally have source levels as low as possible, below 150 dB re 1 µPa RMS @ 1 m and perceived above ambient noise.

Bacteriological and histopathological findings in cetaceans that stranded in the Philippines from 2017 to 2018.

The relatively high frequency of marine mammal stranding events in the Philippines provide many research opportunities. A select set of stranders (n = 21) from 2017 to 2018 were sampled for bacteriology and histopathology. Pertinent tissues and bacteria were collected from individuals representing eight cetacean species (i.e. Feresa attenuata, Kogia breviceps, Globicephala macrorhynchus, Grampus griseus, Lagenodelphis hosei, Peponocephala electra, Stenella attenuata and Stenella longirostris) and were subjected to histopathological examination and antibiotic resistance screening, respectively. The antibiotic resistance profiles of 24 bacteria (belonging to genera Escherichia, Enterobacter, Klebsiella, Proteus, and Shigella) that were isolated from four cetaceans were determined using 18 antibiotics. All 24 isolates were resistant to at least one antibiotic class, and 79.17% were classified as multiple antibiotic resistant (MAR). The MAR index values of isolates ranged from 0.06 to 0.39 with all the isolates resistant to erythromycin (100%; n = 24) and susceptible to imipenem, doripenem, ciprofloxacin, chloramphenicol, and gentamicin (100%; n = 24). The resistance profiles of these bacteria show the extent of antimicrobial resistance in the marine environment, and may inform medical management decisions during rehabilitation of stranded cetaceans. Due to inadequate gross descriptions and limited data gathered by the responders during the stranding events, the significance of histopathological lesions in association with disease diagnosis in each cetacean stranding or mortality remained inconclusive; however, these histopathological findings may be indicative or contributory to the resulting debility and stress during their strandings. The findings of the study demonstrate the challenges faced by cetacean species in the wild, such as but not limited to, biological pollution through land-sea movement of effluents, fisheries interactions, and anthropogenic activities.

Justice for the Menopause: A Research Agenda


 
 
 Menopause is defined by its relationship to menstruation––it is the cessation of menstruation. Medical texts identify menopause as part of the cycle of “decay” associated with female reproductive functions; early menopause is often a dreaded result of various medical treatments and a sign of disfunction.
 It turns out that only three types of animals experience menopause: killer whales, short-finned pilot whales, and humans, while other animals can reproduce until death. Although the precise relationship between evolutionary theory and the physical development of human menopause is still uncertain, scientists and anthropologists suggest that the “grandmother hypothesis” provides a partial explanation: older women, who can no longer produce their own children, ensure their genetic legacy by playing a critical role in helping to feed, raise, and nurture their grandchildren.
 
 
 
 The average woman will spend almost as many years “post-menopause” as they will menstruating, and they may spend four years (or more) experiencing perimenopausal symptoms, the transition time between “normal” menstruation and menopause. But legal issues relating to perimenopause, menopause, and post-menopause are just beginning to surface, prompted by the movement towards menstrual justice, feminist jurisprudence, and developments in the law of aging.
 This Essay is an initial effort to catalogue various legal approaches to menopause and to set out areas for further analysis. It briefly explores cultural images of menopause and post-menopausal women, including the ubiquitous hot flashes; analyzes potential legal claims for menopausal justice; and suggests the interrelationship between such approaches and social attitudes towards menopause. It suggests that “normalizing” menopause––acknowledging its realities––is one means for removing the associated stigma and “disabilities” and might result in reinterpreting existing laws and guiding future legal reforms.
 
 
 
 
 

EFFICACY OF HUMAN RECOMBINANT GRANULOCYTE COLONY-STIMULATING FACTOR (G-CSF, FILGRASTIM; NEUPOGEN®) IN NEUTROPENIC CETACEANS.

Neutrophils are one of the initial cell lines of protection against pathogens, and when their concentrations in the blood are low, animals are highly susceptible to infections. Neutropenia has been reported in cetaceans secondary to administration of systemic sulfa antibiotics or antifungal medications and severe, overwhelming infection. Filgrastim was administered to treat neutropenia over a 15-y period in 11 cetaceans comprising four species-beluga (Delphinapterus leucas, n = 1), bottlenose dolphin (Tursiops truncatus, n = 4), killer whale (Orcinus orca, n = 5), and short-finned pilot whale (Globicephala macrorhynchus, n = 1)] ranging in age from 1 wk to >24 y. Seven study animals received multiple doses (2-6). All animals responded to at least one dose (1-7 µg/kg) of parenteral filgrastim characterized by an increase in peripheral immature (band) neutrophils, segmented neutrophils, or both. In most cases (9/11), neutrophil counts increased within 48 h of a single dose. Duration of response varied but was at least 2 wk in eight of the 11 animals and 5-9 d in the remaining animals. No adverse reactions were observed in any cases.

Cetaceans of the Northern Bismarck Sea, Papua New Guinea1

There is little known about cetaceans in the waters of Papua New Guinea (PNG). Here we present findings from the first two sets of cetacean sighting and acoustic surveys conducted within the Admiralty Island group in the northern Bismarck Sea. More than 1,000 cetaceans were sighted during our boat-based surveys–the most common being spinner dolphins (Stenella longirostris), followed by pantropical spotted dolphins (Stenella attenuata), short-finned pilot whales (Globicephala macrorhynchus), and sperm whales (Physeter macrocephalus). The relative group size of spinner dolphins was different between years with group sizes in 2010 being significantly lower (median = 15, range = 2–50) than those recorded in 2013 (median = 50, range = 5–100). The presence of large aggregations of spinner dolphins (including calves) as well as sightings of Vulnerable sperm whales suggest the northern Bismarck Sea as an area of conservation importance for cetaceans. Our surveys also provide useful baseline data for a variety of marine protected area planning processes and management initiatives that are ongoing in PNG.

Multiple‐model stock assessment frameworks for precautionary management and conservation on fishery‐targeted coastal dolphin populations off Japan

Abstract Stock assessment approaches are often oversimplified due to lack of biological knowledge and insufficient data. In spite of world‐wide attention, fishery‐targeted coastal dolphin species in Japan have lacked in‐depth quantitative stock assessments because of limited time series of population size and an absence of associated biological information. We consequently developed integrated population models that analysed multiple sources of data simultaneously with published biological information within a Bayesian framework. We estimate population status and trends for three main species targeted by fisheries, bottlenose dolphins Tursiops truncatus, Risso's dolphins Grampus griseu, and short‐finned pilot whales Globicephala macrorhynchus, using single‐species age‐aggregated and age‐structured population dynamics models. Models were fit to absolute abundance estimates from systematic line‐transect surveys, four series of abundance indices calculated from fisher's logbooks, and historical catch records. Published biological information was used to develop prior distributions for the biological parameters. We assessed the possible effects of ecological disturbance and competition using state‐space and multispecies models. The multispecies model was selected by the model selection both for the age‐aggregated and the age‐structured approaches. Single‐species assessments found that population size declined 4.2% (Risso's dolphin) to 8.0% (bottlenose dolphin) for three species since the late 1800s based on median posterior values, while the state‐space and multispecies models found that environmental disturbance and an interaction among species could have reduced population size more substantially. Policy implications. Simple single‐species models are often used to provide conservation and management advice for wild animals but, in this case, results from such models are overly optimistic because they overlook important ecological process. In contrast, current population status could be less favorable if environmental disturbance and interspecific competition actually control population dynamics. Even if that is not the case, considering ecological process in the model will provide more precautionary ways. Our approach of combining multiple modelling frameworks is applicable to many other management systems, and offers increased confidence in estimated status and trends over assessments that consider only a single model.

Numerical-modeling-based investigation of sound transmission and reception in the short-finned pilot whale (Globicephala macrorhynchus)

The sound-transmission, beam-formation, and sound-reception processes of a short-finned pilot whale (Globicephala macrorhynchus) were investigated using computed tomography (CT) scanning and numerical simulation. The results showed that sound propagations in the forehead were modulated by the upper jaw, air components, and soft tissues, which attributed to the beam formation in the external acoustic field. These structures owned different acoustic impedance and formed a multiphasic sound transmission system that can modulate sounds into a beam. The reception pathways composed of the solid mandible and acoustic fats in the lower head conducted sounds into the tympano-periotic complex. In the simulations, sounds were emitted in the forehead transmission system and propagated into water to interrogate a steel cylinder. The resulting echoes can be interpreted from multiple perspectives, including amplitude, waveform, and spectrum, to obtain the acoustic cues of the steel cylinder. By taking the short-finned pilot whale as an example, this study provides meaningful information to further deepen our understanding of biosonar system operations, and may expand sound-reception theory in odontocetes.

Climate change vulnerability of cetaceans in Macaronesia: Insights from a trait-based assessment

Over the last decades global warming has caused an increase in ocean temperature, acidification and oxygen loss which has led to changes in nutrient cycling and primary production affecting marine species at multiple trophic levels. While knowledge about the impacts of climate change in cetacean's species is still scarce, practitioners and policymakers need information about the species at risk to guide the implementation of conservation measures.To assess cetacean's vulnerability to climate change in the biogeographic region of Macaronesia, we adapted the Marine Mammal Climate Vulnerability Assessment (MMCVA) method and applied it to 21 species management units using an expert elicitation approach.Results showed that over half (62%) of the units assessed presented Very High (5 units) or High (8 units) vulnerability scores. Very High vulnerability scores were found in archipelago associated units of short-finned pilot whales (Globicephala macrorhynchus) and common bottlenose dolphins (Tursiops truncatus), namely in the Canary Islands and Madeira, as well as Risso's dolphins (Grampus griseus) in the Canary Islands. Overall, certainty scores ranged from Very High to Moderate for 67% of units.Over 50% of units showed a high potential for distribution, abundance and phenology changes as a response to climate change.With this study we target current and future information needs of conservation managers in the region, and guide research and monitoring efforts, while contributing to the improvement and validation of trait-based vulnerability approaches under a changing climate.

Cetacean Research and Citizen Science in Kenya

In 2011, several non-governmental and government agencies established the Kenya Marine Mammal Network (KMMN) to provide a platform for the consistent collection of data on marine mammals along the Kenyan coast, identify areas of importance and engage marine users and the general public in marine mammal conservation. Prior to the KMMN, relatively little was known about marine mammals in Kenya, limiting conservation strategies. The KMMN collects data nationwide through dedicated surveys, opportunistic sightings and participative citizen science, currently involving more than 100 contributors. This paper reviews data on sightings and strandings for small cetaceans in Kenya collated by the KMMN. From 2011 to 2019, 792 records of 11 species of small cetaceans were documented. The most frequently reported inshore species were the Indo-Pacific bottlenose dolphin and Indian Ocean humpback dolphin. Offshore species, included killer whales, short-finned pilot whale and long-snouted spinner dolphin. Indo-Pacific bottlenose dolphins, long-snouted spinner dolphins, striped dolphins and Risso’s dolphins were recorded through stranding reports. The efforts of the KMMN were disseminated through international meetings (International Whaling Commission, World Marine Mammal Conference), national status reports, outreach and social media. Data has also supported the identification of three IUCN Important Marine Mammal Areas and one Area of Interest in Kenya. Further research is needed to improve estimates of cetacean abundance and distribution, particularly in unstudied coastal areas, and to assess the extent of anthropogenic threats associated with fisheries, coastal and port development, seismic exercises and unregulated tourism. The expansion of the network should benefit from the participation of remote coastal fishing communities, government research agencies, tourism and seismic operations, among others. The KMMN demonstrated the value of dedicated and citizen science data to enhance marine mammal conservation strategies to boost awareness and eco-tourism and to bring the public and science closer together, promoting research and effective conservation efforts.

Report of stranded skeletal system of Short-finned Pilot Whale from South Reef Island, Middle Andaman, India

Marine mammals are exceptionally significant animals with innumerable essential ecological roles in global aquatic ecosystems while the evolutionary divergence was taken place from the terrestrial habits. The adaptive radiation in aquatic life endorses various structural modifications in their general organization of body plan. Short-finned Pilot Whales (Globicephala macrorhynchus Gray, 1846) are predominantly distributed mostly in tropical and temperate regions of the world’s oceans as one of the greatest social organisms which travel in higher speed in a group only with several individuals. Such practice of their social life is the prime risk for their population depletion as mass stranding across the world due to natural or anthropogenic threats while stranding of a single individual is a rare occurrence for this species and resulted mostly due to disease. During the present study, a stranded skeletal system (incomplete) of Short-finned Pilot Whale containing 49 parts (1 skull, 1 lower mandible, 3 ribs, 37 vertebrae, 1 scapula, 2 humeri, 2 radii, and 2 ulnae) were found at South Reef Island of Andaman and Nicobar Islands. Detailed cranial measurements were taken. Condylobasal length is 56.6 cm. This is the first stranding report of a solitary individual of Short-finned Pilot Whale in Andaman and Nicobar Islands.

Feeding Ecology of Elusive Caribbean Killer Whales Inferred From Bayesian Stable Isotope Mixing Models and Whalers’ Ecological Knowledge

Investigating the feeding ecology of marine predators is critical for understanding their roles and functional importance in ecosystems. However, assessing the diet of large and wide-ranging predators can be challenging, particularly in the case of rare and elusive species. Killer whales (Orcinus orca) are large apex predators in global oceans, but very little is known about their feeding ecology in tropical ecosystems, particularly in the Caribbean Sea. Killer whales are distributed throughout the Caribbean, and are a regular target of artisanal whalers in St. Vincent and the Grenadines (West Indies). Here we investigate the feeding ecology of Caribbean killer whales using a combination of stable isotope analysis (δ15N, δ13C) and traditional ecological knowledge (TEK) data from whalers operating from St. Vincent. Potential prey data from the Caribbean region included large pelagic teleosts, sea turtles, oceanic sharks, cetaceans, and oceanic cephalopods. Mixing models suggest that the contribution of odontocete cetaceans to the diet of killer whales is the most important (overall mean contribution: 60.4%), particularly mesopelagic delphinids (Lagenodelphis hosei; 26.4%, SD = 0.14), large teuthophageous odontocetes (Physeter macrocephalus,Globicephala macrorhynchus; 20.0%, SD = 0.14), and epipelagic delphinids (Stenella attenuata; 14%, SD = 0.14). Oceanic sharks (Carcharhinus longimanus) had a contribution of 17.0% of the diet of killer whales (SD = 0.13), and other potential prey had a relatively marginal contribution. TEK data suggest that whalers believe killer whales feed almost exclusively on cetaceans, particularly odontocete species that they hunt (e.g.,G. macrorhynchus). Stable isotope and TEK data were consistent to some extent, although TEK data are qualitative and based on a limited number of observations. Despite some limitations (including sample size for both methods), this study highlights the value of combining independent data sources and methodologies to investigate the ecological roles of marine predators in data-poor regions.

Circular DNA viruses identified in short-finned pilot whale and orca tissue samples

Members of the Delphinidae family are widely distributed across the world's oceans. We used a viral metagenomic approach to identify viruses in orca (Orcinus orca) and short-finned pilot whale (Globicephala macrorhynchus) muscle, kidney, and liver samples from deceased animals. From orca tissue samples (muscle, kidney, and liver), we identified a novel polyomavirus (Polyomaviridae), three cressdnaviruses, and two genomoviruses (Genomoviridae). In the short-finned pilot whale we were able to identify one genomovirus in a kidney sample. The presence of unclassified cressdnavirus within two samples (muscle and kidney) of the same animal supports the possibility these viruses might be widespread within the animal. The orca polyomavirus identified here is the first of its species and is not closely related to the only other dolphin polyomavirus previously discovered. The identification and verification of these viruses expands the current knowledge of viruses that are associated with the Delphinidae family.