Walrus Research Articles

Assessing the population consequences of disturbance and climate change for the Pacific walrus

Climate change and anthropogenic disturbance are increasingly affecting wildlife at a global scale. Predicting how varying types and degrees of disturbance may interact to influence population dynamics is a key management challenge. Population consequences of disturbance (PCoD) models provide a framework to link effects of anthropogenic disturbance on an individual’s behavior and physiology to population-level changes. In the present study, we develop a Pacific walrus (Odobenus rosmarus divergens) PCoD model to encompass the population-level effects of both anthropogenic disturbance and climate change. As the Arctic becomes increasingly ice-free, walruses spend more time at coastal (vs. ice-based) haulouts, from which they must expend more energy to reach foraging areas and where they have an elevated risk of mortality. Concurrently, sea ice loss is increasing the anthropogenic footprint in the Arctic (e.g. fisheries, shipping, energy exploration), which creates additional disturbance. We applied the PCoD model to 4 scenarios (ranging from optimistic to pessimistic) which incorporate different global sea ice model projections along with varying degrees of anthropogenic disturbance. All scenarios indicated a decline in Pacific walrus vital rates by the end of the 21st century, but our results demonstrated that the intensity of that decline could be mitigated by global efforts to reduce carbon emissions, along with local management and conservation efforts to protect important coastal haulouts and foraging grounds. In summary, we introduce a flexible PCoD modeling framework in a novel context which will prove useful to researchers studying species threatened by rapid environmental change.

Enhancing the accuracy and efficiency of Pacific walrus (Odobenus rosmarus divergens) surveys: A comparison of visual and aerial imagery-based counts at coastal haulouts.

This study presents a semi-automated approach utilizing unoccupied aerial vehicle (UAV) surveys to accurately estimate the abundance of Pacific walruses at large coastal haulouts in Chukotka, Russia. Seven major haulout sites were surveyed during the summers and falls of 2017-2019. Walrus counts were performed using three distinct methods: traditional visual land-based counts, complete head counts utilizing georeferenced UAV imagery, and counting walruses within model polygons within the haulout outline and employing various extrapolation techniques to predict walrus abundance across the haulout area. The results indicated that traditional visual counts neither yielded consistent results nor allowed for uncertainty estimation, unlike the site- and date-specific direct extrapolation method and the non-specific linear regression model. These latter methods consistently provided estimates, on average, within 5% of the "true" abundance determined through complete photo-based head counts. Beside yielding accurate estimates, these semi-automated methods significantly reduced counting time by at least 63%, in contrast to complete head counts. The non-specific model, which allowed the estimation of walrus abundance based on the type of the terrain and the haulout area was less accurate compared with site and date specific estimates, but provided a tool to estimate abundance when no field visits are conducted, e.g., by using high-resolution satellite imagery to measure haulout area. This model revealed that the haulouts located on flat sandy beaches exhibited mean walrus densities approximately 30.5% times higher than those on rocky shores surrounded by cliffs: 0.879 (SD = 0.1302) and 0.648 (SD = 0.1753) walrus per m2 correspondingly. The estimated daily walrus abundance at major Chukotkan haulouts in 2017-2019 ranged between 15 and 94,660 (mean = 10,397, SD = 14,477) walruses with the maximum seasonal abundances reported at Cape Serdtse-Kamen as 94,960 on 10-Oct-2017, 26,850 on 10-Oct-2018, and 87,595 on 10-Oct-2019.

Interannual site fidelity by Svalbard walruses

The Arctic is experiencing rapid reductions in sea ice, affecting all ice-dependant species. In the present study we examine interannual seasonal movements and habitat use in relation to sea ice coverage for one of the Arctic endemic marine mammals. We tagged 40 male walruses (Odobenus rosmarus) in the Svalbard Archipelago with custom-designed tusk-mounted GPS loggers. Twelve of these animals provided tracks that lasted 1–6 years. Eleven of the walruses displayed clear seasonal migratory behaviour between summer foraging areas and winter breeding areas. Individuals showed high inter-individual variation, but clear site fidelity, using the same areas in consecutive years despite variable sea ice conditions. The walruses swam 5225–10,406 km per year and travelled remarkably similar distances between years on an individual basis. The phenology of migration was not impacted by sea ice concentrations or daylight length but was consistent at the individual level, suggesting endogenous drivers. Sea ice concentrations influenced movement behaviour with animals showing more tortuous paths when in areas with heavy sea ice, possibly searching for polynyas where females reside. Ongoing climate change is expected to drastically change walrus habitat, and it remains to be seen if walruses will be able to shift from their fixed seasonal migratory routines.

Assessment of the current state of the Pacific walrus population based on monitoring work on the coastal rookery «Cape Vankarem» (Chukotka Autonomous District)

The goal of the work: to assess the current state of the Pacific walrus population and other marine mammal species in the Chukchi Sea subzone (the area of the Natural sanctuary «Cape Vankarem»).Problems: obtaining new information about the number, sex and age structure, reproduction rates of walruses in the research area; assessment of the timing and intensity of filling the local rookery; assessment of the level of coastal mortality of marine mammals, age and sex composition of fallen animals; assessment of anxiety factors and the level of their impact on animals; collection of meteorological data in the research area during the research period; scientific support of aboriginal fishing; data collection on other marine mammal species in the research area (cetaceans, real seals); accounting of the number of predators (white and brown bears, killer whales) in the vicinity of the rookery and monitoring their relationship with walruses.Scientific work on the coastal walrus rookery was carried out in the area of the Cape Vankarem (the Arctic coast of the Chukchi Sea), from August 15 to October 2, 2023.Practical significance of the research: assessment of the current state of the local grouping of Pacific walruses, the level of natural loss and reproductive ability of the grouping; data for regulating fishing, increasing its efficiency and ensuring the conditions of traditional nature use of the indigenous population of Chukotka.

A contribution to lipid digestion of Odobenidae family: Computational analysis of gastric and pancreatic lipases from walrus (Odobenus rosmarus divergens)

Triacylglycerols (TAGs) are a primary energy source for marine mammals during lipid digestion. Walruses (Odobenus rosmarus divergens) consume prey with a high content of long-chain polyunsaturated fatty acids; however, their digestive physiology and lipid digestion remain poorly studied. The present study aims to model and characterize the gastric (PWGL) and pancreatic (PWPL) lipases of Pacific walruses using an in-silico approach. The confident 3D models of PWGL and PWPL were obtained via homology modeling and protein threading and displayed the structural features of lipases. Molecular docking analysis demonstrated substrate selectivity for long-chain TAG (Trieicosapentaenoin; TC20:5n-3) in PWGL and short-chain TAG (Trioctanoin; TC8:0) in PWPL. Molecular dynamics simulations demonstrate that PWGL bound to tridocosahexaenoin (TC22:6n-3), the protein is considerably stable at all three salinity conditions, but fluctuations are observed in the regions associated with catalytic sites and the lid, indicating the potential hydrolysis of the substrate. This is the first study to report on the digestion of TAGs in walruses, including modeling and lipases characterization and proposing a digestive tract for pinnipeds.

Ecosystem structure and function of the North Water Polynya

The North Water Polynya is one of the most productive Arctic regions on Earth, sustaining the world's northernmost Inuit communities for millennia. The polynya is a large and persistent region of open water surrounded by sea ice and exhibits high primary productivity, is a biodiversity hotspot, and is a key habitat and migration corridor for Arctic species. Many aspects of the ecosystem structure and the role of resident species in the North Water Polynya remain uncertain. To shed light on these, we developed the first representation of the North Water Polynya food web using the Ecopath modelling framework. Modelled trophic flows indicated that pelagic and benthic communities were primarily connected by Age 1+ Arctic cod ( Boreogadus saida), walrus ( Odobenus rosmarus), and ringed seal ( Pusa hispida). Large copepods, Age 1+ Arctic cod, and bivalves were key prey species. Overall productivity in the North Water Polynya was higher compared to Western Baffin Bay and Western Greenland, corroborating expectations of relatively high productivity within the polynya. This model provides a baseline description of the North Water Polynya ecosystem structure and function prior to future climate-driven food web changes and the emergence of large-scale commercial fisheries.

Seasonal and diurnal marine mammal presence in the proposed marine protected area of Southampton Island, Hudson Bay, Nunavut as revealed by passive acoustic monitoring

Marine protected areas contribute to mitigating the effects of human activities on marine ecosystems. The waters of Southampton Island, Nunavut, Canada are under consideration to become a marine protected area, but baseline information of marine mammal presence and habitat use is lacking. This study represents the first passive acoustic monitoring of marine mammals in this area, with data collected in 2018 and 2019. Bioacoustics analyses and generalized linear models were used to investigate species seasonal and temporal vocalization trends; infer behavior and habitat use from vocal cues; and explore vocal activity correlation with sea ice. Over a diel period, bearded seals ( Erignathus barbatus (Erxleben, 1777)) and walruses ( Odobenus rosmarus (Linnaeus, 1758)) were found to increase their vocal activity at night, whereas belugas ( Delphinapterus leucas (Pallas, 1776)) mainly vocalized during daytime. Seasonally, bearded seals were recorded only during their breeding season at sea ice break-up, while walruses vocalized consistently throughout the open-water period outside their breeding season. Beluga vocal trends suggest their use of the area as a migratory corridor during sea ice break-up and freeze-up. Finally, bowhead whales ( Balaena mysticetus Linnaeus, 1758) were recorded later than expected, concurrently with the onset of their mating vocal displays during the fall migration at sea ice freeze-up.

Physiological values of phagocytic capacity in marine mammals and alterations during pathological situations.

The study of the immune function in marine mammals is essential to understand their physiology and can help to improve their welfare in the aquariums. Dedicating efforts to studying marine mammal physiology, pathophysiology, and implementing new diagnostic and therapeutic tools promote progress towards preventive medicine in aquariums by facilitating early detection and treatment of diseases. However, biological and clinical research on marine mammals is currently very limited due to difficult access to these species and their biological samples. With this objective, our group has adapted to marine mammals a commercially available assay routinely used to evaluate the phagocytic capacity of monocytes and granulocytes in human whole blood samples. We adapted IngoflowEx kit to bottlenose dolphins (Tursiops truncatus), beluga whales (Delphinapterus leucas), walruses (Odobenus rosmarus), Patagonian sea lions (Otaria flavescens), and harbor (Phoca vitulina). In this paper, we report the modifications carried out on the original protocol for their correct functioning in marine mammals. We obtained physiological values of phagocytic capacity in each species after repeated sampling for 4 years in various individuals of each species. Specific results revealed that the % phagocytic cells that ingested E.coli in bottlenose dolphins were 59.6 ± 1.27, in walruses 62.6 ± 2.17, in sea lions 57.5 ± 4.3, and in beluga whales 61.7 ± 1.4. In the case of the % phagocytic cells producing respiratory burst in bottlenose dolphins were 34.2 ± 3.6, in walruses 36.3 ± 4.3, in sea lions 40.8 ± 10.2, and in beluga whales 26.3 ± 3.7. These preliminary results can be used as a reference to detect alterations in phagocytic capacity either by immunosuppression or by exacerbation of the response in infectious inflammatory processes. Clinical applicability of the assay was verified in two clinical cases in which Ingoflow was useful to detect immune alterations in two diseased individuals, before and after the onset of clinical signs.

Archaeological evidence of resource utilisation of walrus, Odobenus rosmarus, over the past two millennia: A systematic review protocol.

The walrus, Odobenus rosmarus, is an iconic pinniped and predominant molluscivore that is well adapted to Arctic and subarctic environments. Its circumpolar distribution, large body size and ivory tusks facilitated its vital role as food, raw material (for tools and art), income, and cultural influence on many Arctic Indigenous communities for millennia. Intensification of hunting (often due to the arrival of Europeans, especially between the 16 th and 19 th centuries) to obtain ivory, hide, blubber and meat, resulted in diminished, sometimes extirpated, walrus populations. Zooarchaeological, artefactual and documentary evidence of walrus material has been collated at local and regional scales and is frequently focused on a specific culture or period of time. Systematic collation of this evidence across the Northern Hemisphere will provide insight into the chronology and circumpolar distribution of walrus hunting and provide a tool to document societal change in walrus resource use. Here, we lay out a systematic review protocol to collate records of archaeological walrus artefacts, tusks and bones that have been documented primarily within published literature to archive when and where (as feasible) walrus extractions occurred between 1 CE and 2000 CE. These data will be openly available for the scientific community. The resulting dataset will be the first to provide spatiotemporal information (including the recognition of knowledge gaps) regarding past walrus populations and extirpations on a circumpolar scale. Our protocol is published to ensure reproducibility and comparability in the future, and to encourage the adoption of systematic review methodology (including pre-published protocols) in archaeology.

Ancient DNA indicates a century of overhunting did not reduce genetic diversity in Pacific Walruses (Odobenus rosmarus divergens)

Pacific Walruses (Odobenus rosmarus divergens [Illiger 1815]) are gregarious marine mammals considered to be sentinels of the Arctic because of their dependence on sea ice for feeding, molting, and parturition. Like many other marine mammal species, their population sizes were decimated by historical overhunting in the nineteenth and twentieth centuries. Although they have since been protected from nearly all commercial hunting pressure, they now face rapidly accelerating habitat loss as global warming reduces the extent of summer sea ice in the Arctic. To investigate how genetic variation was impacted by overhunting, we obtained mitochondrial DNA sequences from historic Pacific Walrus samples in Alaska that predate the period of overhunting, as well as from extant populations. We found that genetic variation was unchanged over this period, suggesting Pacific Walruses are resilient to genetic attrition in response to reduced population size, and that this may be related to their high vagility and lack of population structure. Although Pacific Walruses will almost certainly continue to decline in number as the planet warms and summer sea ice is further reduced, they may be less susceptible to the ratcheting effects of inbreeding that typically accompany shrinking populations.

Insights into carbonate environmental conditions in the Chukchi Sea

Abstract. Healthy Arctic marine ecosystems are essential to the food security and sovereignty, culture, and wellbeing of Indigenous Peoples in the Arctic. At the same time, Arctic marine ecosystems are highly susceptible to impacts of climate change and ocean acidification. While increasing ocean and air temperatures and melting sea ice act as direct stressors on the ecosystem, they also indirectly enhance ocean acidification, accelerating the associated changes in the inorganic carbon system. Yet, much is to be learned about the current state and variability of the inorganic carbon system in remote, high-latitude oceans. Here, we present time series (2016–2020) of pH and the partial pressure of carbon dioxide (pCO2) from the northeast Chukchi Sea continental shelf. The Chukchi Ecosystem Observatory includes a suite of subsurface year-round moorings sited amid a biological hotspot that is characterized by high primary productivity and a rich benthic food web that in turn supports coastal Iñupiat, whales, ice seals, walrus (Odobenus rosmarus), and Arctic cod (Boreogadus saida). Our observations suggest that near-bottom waters (33 m depth, 13 m above the seafloor) are a high carbon dioxide and low pH and aragonite saturation state (Ωarag) environment in summer and fall, when organic material from the highly productive summer remineralizes. During this time, Ωarag can be as low as 0.4. In winter, when the site was covered by sea ice, pH was <8 and Ωarag remained undersaturated under the sea ice. There were only two short seasonal periods with relatively higher pH and Ωarag, which we term ocean acidification relaxation events. In spring, high primary production from sea ice algae and phytoplankton blooms led to spikes in pH (pH > 8) and aragonite oversaturation. In late fall, strong wind-driven mixing events that delivered low-CO2 surface water to the shelf also led to events with elevated pH and Ωarag. Given the recent observations of high rates of ocean acidification and a sudden and dramatic shift of the physical, biogeochemical, and ecosystem conditions in the Chukchi Sea, it is possible that the observed extreme conditions at the Chukchi Ecosystem Observatory are deviating from the carbonate conditions to which many species are adapted.

Deviations in the Development of Captivity Walrus (Odobenus rosmarus) Skull

Deviations in the Development of Captivity Walrus (Odobenus rosmarus) Skull

3000 leagues under the sea: the voyages of vagrant walruses (Odobenus rosmarus) in temperate Europe

Sightings of vagrant walruses in Europe have been known since historic times, yet whether this phenomenon remains constant or changes over time is unclear. In this study, we conducted a comprehensive cross-reference of information on vagrant walruses observed in temperate Europe (below 61° N) between 1923 and 2022 utilising data from the Global Biodiversity Information Facility depository. In addition, we conducted an online search of records from the last ten years, resulting in a detailed reconstruction of the movements of the most recently observed individuals. We estimated that between 31 and 36 different individuals have been observed over the last century, with most of these likely originating from the Svalbard region and only a few from Greenland. A comparison in the yearly number of records showed a significant increase over time, suggesting that vagrant walruses reach Europe as a result of a combination of climatic and meteorological events as well as of demographic changes in the populations of the North Atlantic.

The movement patterns and foraging resources of Atlantic walruses (Odobenus rosmarus rosmarus) in Franz Josef Land archipelago and connectivity with the Kara‐Barents Sea population

AbstractThe Franz Josef Land population of the Atlantic walrus (Odobenus rosmarus rosmarus) remains one of the least studied. Here, 26 walruses were tagged with satellite‐linked radio transmitters in Franz Josef Land archipelago and Victoria Island in summer‐autumn 2020 and 2021 to assess movements patterns and area utilization. In addition, 65 grab samples were taken to evaluate macrobenthic foraging resources. The mean duration of data records was 53 ± 27 days. The walruses traveled on average 29 ± 13.5 km/day with a mean speed of 1.2 ± 0.6 km/hr. The travel speed and distance were statistically different for male, female, and immature walruses. The individuals tagged on Victoria Island remained in the vicinity of the island, while walruses tagged within the Franz Josef Land archipelago moved between the islands, utilizing the entire area for foraging trips. One walrus migrated from Franz Josef Land to Novaya Zemlya in late November, providing evidence of connectivity with the Kara‐Barents Sea population. The area was characterized by high average biomass of macrobenthos. Bivalve mollusks, Hiatella arctica, were dominating macrobenthic biomass, likely being the main foraging resource for the walruses. Further observations are needed to better understand winter behaviors of Franz Josef Land walruses and possible impacts of climate change on movement patterns.

New species of Ontocetus (Pinnipedia: Odobenidae) from the Lower Pleistocene of the North Atlantic shows similar feeding adaptation independent to the extant walrus (Odobenus rosmarus).

Ontocetus is one of the most notable extinct odobenines owing to its global distribution in the Northern Hemisphere. Originating in the Late Miocene of the western North Pacific, this lineage quickly spread to the Atlantic Ocean during the Pliocene, with notable occurrences in England, Belgium, The Netherlands, Morocco and the eastern seaboard of the United States. Reassessment of a pair of mandibles from the Lower Pleistocene of Norwich (United Kingdom) and a mandible from the Upper Pliocene of Antwerp (Belgium) that were referred to as Ontocetus emmonsi reveals existences of features of both Ontocetus and Odobenus. The presence of four post-canine teeth, a lower canine larger than the cheek-teeth and a lower incisor confirms the assignment to Ontocetus; simultaneously, characteristics such as a fused and short mandibular symphysis, a well-curved mandibular arch and thin septa between teeth align with traits usually found in Odobenus. Based on a combination of these characters, we describe Ontocetus posti, sp. nov. Its mandibular anatomy suggests, a better adaptation to suction-feeding than what was previously described in the genus suggesting that Ontocetus posti sp. nov. likely occupied a similar ecological niche to the extant walrus Odobenus rosmarus. Originating from the North Pacific Ocean, Ontocetus most likely dispersed via the Central American Seaway. Although initially discovered in the Lower Pliocene deposits of the western North Atlantic, Ontocetus also left its imprint in the North Sea basin and Moroccan Plio-Pleistocene deposits. The closure of the Isthmus of Panama during the Mio-Pliocene boundary significantly impacted the contemporary climate, inducing global cooling. This event constrained Ontocetus posti in the North Sea basin leaving the taxon unable to endure the abrupt climate changes of the Early Pleistocene, ultimately going extinct before the arrival of the extant counterpart, Odobenus rosmarus.

Odobenus rosmarus divergens (Odobenidae) groups in the waters adjacent to coastal haulouts (Chukchi Peninsula, Russia)

The distance between individuals is one of the key characteristics of the spatial structure of a group. Here, we investigated inter-individual distances in Odobenus rosmarus divergens (hereinafter – walrus) aggregations in waters adjacent to four coastal haulouts in the Chukchi Sea, Russia. The analysis of aerial images showed that the majority of the individuals in water were in tight groups (binomial z > 11.37, p < 0.001), in which the distances between walruses were significantly shorter than those outside such groups (LMM coefficient ± SE: 0.14 ± 0.03; p < 0.001). The number of individuals within the groups did not influence the inter-individual distances (LMM coefficient ± SE: 0.05 ± 0.05; p = 0.376) and the density of them was similar across haulouts studied (omnibus χ2(3) = 7.78, p = 0.051). The water areas adjacent to haulouts may provide optimal conditions for social interactions of walruses and potentially play an important role in their social life. The investigation of walrus aggregations in water may become increasingly important in the context of the reducing Arctic ice cover.

Pleistocene Walrus (<i>Odobenus rosmarus</i> L., 1758) Discovered in the Northern European Russia (Pechora River)

A fragment of a walrus skull of Neopleistocene age was found at a distance of about 340 km from the mouth of the Pechora River. The skull presumably belonged to a mature male of Atlantic walrus 13–14 years old. The radiocarbon date of the walrus bone shows the age over the method’s limit (45 ka). Nitrogen and carbon isotope data from skull collagen are discussed. The reason for the appearance of the walrus far from the modern sea shore was, presumably, the Rodionovo (Shklov, MIS 7) or boreal Sula (Mikulino, MIS 5e) marine transgression into the area of the latitudinal part of the Pechora River. The relatively good preservation of bone testifies in favor of the Sula marine transgression. The Rodionovo age of the walrus can be assumed on the basis of the presence of shallow water marine deposits lying between two Middle Pleistocene moraines—Pechora (Dnieper, MIS 8) and Vychegda (Moscow, MIS 6).

Monitoring platelet function in marine mammals: Intracellular Ca2+ mobilization as a biomarker of platelet activation

Platelet functionality plays a crucial role in marine mammals. Alterations in platelet function can result from stress, pathologies, or exposure to xenobiotics, among others. The early detection of platelet function abnormalities is essential in these species to prevent advanced pathology and mitigate potential risks. Our main objective was to establish a range of physiological values of platelet function in bottlenose dolphins (Tursiops truncatus), beluga whales (Delphinapterus leucas), sea lions (Otaria flavescens) and walruses (Odobenus rosmarus). Intraplatelet Ca2+ mobilization using adenosine diphosphate (ADP) as a platelet agonist was used as a platelet function biomarker, adapting the methodology previously described by us in dolphins (Felipo-Benavent et al., 2022) to the rest of the species. The assay was also adapted to a seal (Phoca vitulina). Numerical indicators of intraplatelet Ca2+ mobilization kinetics were established, and statistical analyses were performed to compare the effects of species, sex, age, aquarium and species. Significant differences were observed between species, being the platelets of the sea lions the more reactive to the agonist. This work demonstrates the usefulness of this assay in the diagnosis or monitoring of animals with hemostatic diseases, showing two clinical cases in which intraplatelet calcium mobilization values were altered in marine mammals suffering haemorrhages. This assay may also serve as a means to monitor environmental changes and their potential impact on the health of marine mammal populations.

Validation of satellite imagery for quantitative population assessment and monitoring of Atlantic walrus

Monitoring animal population abundance and distribution is essential for conservation and management. Recent advances in very high-resolution (VHR) satellite imagery allow for unprecedented detection and identification of animals, offering a potential alternative to conventional methods of population assessment such as aerial surveys. Here, we compare satellite and aerial survey images of a terrestrial walrus haul-out site in the Canadian High Arctic taken 1.5 h apart. While the 30-cm resolution of the commercially available satellite image was insufficient to reliably count individual walruses visually, a manual digitization method successfully identified and delineated image areas confirmed visually to have walrus. Estimates of numbers of hauled out walrus obtained by multiplying the detected area by a range of densities in the aerial image (231) agreed well with actual counts in 35 and 55 mm aerial images (217–240). Potential applications of this approach include quantitative abundance estimation or more simple monitoring of presence/absence over large expanses of remote areas that are logistically difficult to cover using survey aircraft.

Microsatellites and the Major Histocompatibility Complex of the Atlantic Walrus Odobenus rosmarus rosmarus (Linnaeus, 1758) in Haulouts of the Barents Sea

Microsatellites and the Major Histocompatibility Complex of the Atlantic Walrus Odobenus rosmarus rosmarus (Linnaeus, 1758) in Haulouts of the Barents Sea