Walrus Research Articles

Holocene deglaciation drove rapid genetic diversification of Atlantic walrus.

Rapid global warming is severely impacting Arctic ecosystems and is predicted to transform the abundance, distribution and genetic diversity of Arctic species, though these linkages are poorly understood. We address this gap in knowledge using palaeogenomics to examine how earlier periods of global warming influenced the genetic diversity of Atlantic walrus (Odobenus rosmarus rosmarus), a species closely associated with sea ice and shallow-water habitats. We analysed 82 ancient and historical Atlantic walrus mitochondrial genomes (mitogenomes), including now-extinct populations in Iceland and the Canadian Maritimes, to reconstruct the Atlantic walrus' response to Arctic deglaciation. Our results demonstrate that the phylogeography and genetic diversity of Atlantic walrus populations was initially shaped by the last glacial maximum (LGM), surviving in distinct glacial refugia, and subsequently expanding rapidly in multiple migration waves during the late Pleistocene and early Holocene. The timing of diversification and establishment of distinct populations corresponds closely with the chronology of the glacial retreat, pointing to a strong link between walrus phylogeography and sea ice. Our results indicate that accelerated ice loss in the modern Arctic may trigger further dispersal events, likely increasing the connectivity of northern stocks while isolating more southerly stocks putatively caught in small pockets of suitable habitat.

Novel peeling skin condition in neonatal Pacific walruses, Saint Lawrence Island, Alaska, USA.

We describe here a novel peeling skin condition (PSC) in 2 neonatal Pacific walruses (Odobenus rosmarus subsp. divergens). Macroscopically, calves had various degrees of peeling skin exacerbated by mechanical trauma. Lesions occurred in areas subject to friction: ventrum, fore- and hindflippers, and associated joints. Histopathologic features included pseudocarcinomatous epithelial hyperplasia with orthokeratotic hyperkeratosis. Bacterial cocci were present within the stratum corneum. A few intraepidermal clefts were present. Inflammation, epidermolysis, and vasculopathies were not observed. PCR assays were negative for vesivirus and for Staphylococcus aureus exfoliative and toxic shock syndrome toxins. Tissue samples were cultured and bacteria isolated and identified by MALDI-TOF MS as Carnobacterium maltaromaticum, Psychrobacter phenylpyruvicus, Globicatella sanguinis, Streptococcus phocae, Pseudomonas spp., Rahnella aquatilis, and Escherichia coli. Given the young age of the calves and their clinical presentation, congenital ichthyosis was suspected. No genetic differences were detected for sequenced portions of keratin genes (keratin gene K10) between diseased and normal walrus skin. This rare PSC in neonatal Pacific walruses is recognized as novel by indigenous Alaskan marine mammal hunters of the Bering Strait region. A comprehensive diagnostic work-up of future case materials is needed to characterize the underlying biochemical defect(s).

Auditory masking in odobenid and otariid carnivoresa).

As the only living species within the odobenid lineage of carnivores, walruses (Odobenus rosmarus) have no close relatives from which auditory information can be extrapolated. Sea lions and fur seals in the otariid lineage are the nearest evolutionary outgroup. To advance understanding of odobenid and otariid hearing, we conducted behavioral testing with two walruses and one California sea lion (Zalophus californianus). Detection thresholds for airborne sounds were measured from 0.08 to at least 16 kHz in ambient noise conditions and then re-measured in the presence of octave-band white masking noise. Walruses were more sensitive than the sea lion at lower frequencies and less sensitive at higher frequencies. Critical ratios for the walruses ranged from 20 dB at 0.2 kHz to 32 dB at 10 kHz, while critical ratios for the sea lion ranged from 16 dB at 0.2 kHz to 35 dB at 32 kHz. The masking values for these species are comparable to one another and to those of terrestrial carnivores, increasing by about 3 dB per octave with increasing frequency. Despite apparent differences in hearing range and sensitivity, odobenids and otariids have a similar ability to hear signals in noisy conditions.

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

The allelic diversity of the DQB gene of the major histocompatibility complex (MHC) in Atlantic walrus from the European part of the Arctic was analyzed for the first time. We studied animals from the haulouts located on the Franz Josef Land archipelago and near the northern tip of Novaya Zemlya. We demonstrated that there are significant differences for this locus between the two studied haulouts. Simultaneous analysis of microsatellite loci reveals a lower level of differentiation, and also suggest that animals from more than one spatial-geographical stock (population) gather at the summer haulout on Novaya Zemlya. It has been suggested that individuals with different MHC genotypes may prefer different feeding areas, regardless of the areas of residence during the breeding season.

Effects of feeding and habitat on resting metabolic rates of the Pacific walrus

AbstractArctic marine mammals live in a rapidly changing environment due to the amplified effects of global warming. Pacific walruses (Odobenus rosmarus divergens) have responded to declines in Arctic sea‐ice extent by increasingly hauling out on land farther from their benthic foraging habitat. Energy models can be useful for better understanding the potential implications of changes in behavior on body condition and reproduction but require behavior‐specific metabolic rates. Here we measured the resting metabolic rates (RMR) of three captive, adult female Pacific walruses through breath‐by‐breath respirometry when fed and fasted resting out of water (sitting and lying down) and while fed resting in water. RMR in and out of water were positively related with pretrial energy intake when not fasted and 25% higher than RMR when walruses were fasted and out of water. Overall, RMR was higher than previously estimated for this species. Fasting RMR out of water was only 25% lower than subsurface swimming metabolic rates suggestive of relatively efficient swimming in adult females. Our results identify the importance of considering feeding status and species‐specific differences in affecting metabolic costs. Further research is needed to better understand potential energetic costs of thermoregulation at temperatures experienced by wild walruses.

Giardia and Cryptosporidium in resident wildlife species in Arctic Alaska

Giardia and Cryptosporidium are zoonotic protozoan parasites that can infect humans and other taxa, including wildlife, often causing gastrointestinal illness. Both have been identified as One Health priorities in the Arctic, where climate change is expected to influence the distribution of many wildlife and zoonotic diseases, but little is known about their prevalence in local wildlife. To help fill information gaps, we collected fecal samples from four wildlife species that occur seasonally on the northern Alaska coastline or in nearshore marine waters—Arctic fox (Vulpes lagopus), polar bear (Ursus maritimus), Pacific walrus (Odobenus rosmarus divergens), and caribou (Rangifer tarandus)—and used immunofluorescence assays to screen for Giardia cysts and Cryptosporidium oocysts. We detected Giardia cysts in 18.3% and Cryptosporidium oocysts in 16.5% of Arctic foxes (n = 109), suggesting that foxes may be potentially important hosts in this region. We also detected Giardia cysts in a single polar bear (12.5%; n = 8), which to our knowledge represents the first such report for this species. Neither parasite was detected in walruses or caribou.

Patterns of trace element deposition in beluga whale teeth reflect early life history

Determination of trace element concentrations in continuously growing biological structures such as otoliths, whiskers, and teeth can provide important insight into physiological and ontogenetic processes. We examined concentrations of 11 trace elements (Li, Mg, Mn, Cu, Zn, Se, Rb, Sr, Cs, Ba, Pb) in the annual dentine growth layer groups (GLGs) of teeth of 66 Eastern Canadian Arctic belugas (Delphinapterus leucas). Several of these trace elements displayed clear and consistent patterns in early life, though few longer term trends or signals were present in trace element data for either females or males. Large changes in Sr and Ba concentrations in fetal dentine reflected in utero shifts in element deposition in the teeth of developing belugas. Marked changes in these elements during the first years after birth were likely associated with the onset of nursing and subsequent weaning. Mg, Mn, and Zn also displayed clear and consistent patterns in early life that correlated strongly with dentine stable nitrogen isotope (δ15N) data, suggesting these elements merit further study as potential tools for studying nursing and weaning. Depositional patterns of Zn and Pb, which have been linked to sexual maturation in female Pacific walruses (Odobenus rosmarus divergens), were inconsistent in beluga teeth. Some individuals (including males) displayed patterns strongly resembling those observed in female walruses, whereas many animals did not, perhaps because they had not yet reached sexual maturity. The lack of clear patterns in trace element deposition after the first few years of life may have resulted from pooling samples from multiple populations/regions collected across more than two decades, but may also indicate that elemental concentrations are primarily driven by other, extrinsic processes later in life, and might be useful as biomonitors of environmental element concentrations or tools for delineating population structure.

OCCURRENCE AND COASTAL MORTALITY OF CETACEANS ON THE ARCTIC COAST OF CHUKOTKA PENINSULA IN THE WATERS OF CAPE VANKAREM IN 2017–2021

Six species of cetaceans have been found to occur in the Chukchi Sea adjacent to the Pacific walrus rookery at Cape Vankarem: the Grey whale, the Bowhead whale, the Humpback whale, the Killer whale, the Beluga whale, and the Fin whale. The Humpback whale is noted to have become abundant in the Chukchi Sea in the summer in recent years. The coastal mortality of cetaceans in a 100-km section in the western part of the distribution range of both Gray and Bowhead whales has been established to average 1.66 and 0.3 whales per year, respectively. Mostly young animals of 1–2 years of age appear to die, the main cause of death of which being predation by killer whales. The most common whales in that area in the summer-autumn period are humpback whales, which at the same time form significant concentrations in the coastal waters during the accumulation of the main food items. Both bowhead and gray whales are much less frequent, also being rather irregular to be found, while despite the relative scarcity of encounters these species account for the lion’s share of all dead cetaceans.

Treatment of Worn Tusks Using Metal Crowns in Two Young Captive Walruses (Odobenus Rosmarus).

Two young walruses, recently transferred to the Vancouver Aquarium, presented with severe abrasion to their tusks. The walruses were sedated, and clinical examination and radiographs of the tusks showed that the pulp chambers were not exposed. The tips of the tusks were then prepared to receive metal crowns. Vinyl polysiloxane impressions were obtained and sent to the laboratory for chrome-nickel crown fabrication. A week later, the crowns were cemented onto the tusks and remained in place on follow-up examinations.

No microplastics detected in the first assessment of Atlantic walrus stomachs from Nunavut, Canada

As plastic pollution continues to persist at a global level, the Arctic has drawn increased research interest as a possible sink for marine pollutants. Plastic and microplastics are highly durable and can be transported across vast distances. To date, only a handful of studies have directly assessed microplastics in Arctic mammals. In Canada, it is still unclear whether they show a concrete propensity for microplastic retention and ingestion. Atlantic walruses ( Odobenus rosmarus rosmarus (Linnaeus, 1758)) are economically and culturally important for Inuit and are key predators in Arctic marine ecosystems. Here, we present the first assessment of microplastic pollution in Canadian walruses and the first gastrointestinal assessment of microplastic in walruses globally. Since microplastics accumulate in benthic sediment and animals, we expected that walruses may ingest and retain microplastic contaminants when sifting in search of prey or when eating contaminated bivalves and invertebrates. We detected no microplastics ≥80 µm in our evaluation of 36 walruses from five communities in NU, Canada. Our results suggest that walruses in this region do not retain microplastic particles ≥80 µm in their stomachs, which is consistent with findings in other pinnipeds that have been evaluated in Arctic Canada.

Exploring effects of vessels on walrus behaviors using telemetry, automatic identification system data and matching

AbstractArctic marine mammals have had little exposure to vessel traffic and potential associated disturbance, but sea ice loss has increased accessibility of Arctic waters to vessels. Vessel disturbance could influence marine mammal population dynamics by altering behavioral activity budgets that affect energy balance, which in turn can affect birth and death rates. As an initial step in studying these linkages, we conducted the first comprehensive analysis to evaluate the effects of vessel exposure on Pacific walrus (Odobenus rosmarus divergens) behaviors. We obtained >120,000 h of location and behavior (foraging, in‐water not foraging, and hauled out) data from 218 satellite‐tagged walruses and linked them to vessel locations from the marine automatic identification system (AIS). This yielded 206 vessel‐exposed walrus telemetry hours for comparison to unexposed hours, which we used to assess if vessel exposure altered walrus behavior. We developed a filter to account for misclassification of vessel exposure of telemetered walruses. Then we tested for an effect of vessel exposure on walrus behaviors using a combination of exact and propensity score‐based matching to account for confounding covariates, and we conducted statistical power analyses. We did not detect an effect of vessel exposure on walrus behaviors even when statistical power was high (i.e., for foraging walruses), which may have been due to the sample size‐driven need to define vessel presence within a larger than desired distance (15‐km measured radius) around a walrus. Although this study did not determine at what distance vessel exposure affects walrus behaviors, it provided an upper bound on the distance at which the vessels encountered may disturb foraging walruses. When more situation‐specific information is lacking, this distance could be used as a conservative buffer to maintain between vessels and areas of high use by foraging walruses. Studies on behavioral consequences of closer proximities between walruses and vessels are needed, and our assessments of misclassification rates and statistical power can be used for future studies. We demonstrated that analytical approaches such as matching, which are rarely used in wildlife studies, are particularly useful for testing hypotheses with observational data.

Structure and function of the western Baffin Bay coastal and shelf ecosystem

Arctic marine species, from benthos to fish and mammals, are essential for food security and sovereignty of Inuit people. Inuit food security is dependent on the availability, accessibility, quality, and sustainability of country food resources. However, climate change effects are threatening Inuit food systems through changes in abundance and nutritional quality of locally harvested species, while foundational knowledge of Arctic food webs remains elusive. Here, we summarized scientific knowledge available for the western Baffin Bay coastal and shelf ecosystem by building a food web model using the Ecopath with Ecosim modeling framework. Based on this model, we calculated ecological network analysis indices to describe structure and function of the system. We used Linear Inverse Modeling and Monte Carlo analysis to assess parameter uncertainty, generating plausible parameterizations of this ecosystem from which a probability density distribution for each index was generated. Our findings suggest that the system is controlled by intermediate trophic levels, highlighting the key role of Arctic cod (Boreogadus saida) as prey fish, as well as the importance of other less studied groups like cephalopods in controlling energy flows. Most of the ecosystem biomass is retained in the system, with very little lost to subsistence harvest and commercial fisheries, indicating that these activities were within a sustainable range during the modeling period. Our model also highlights the scientific knowledge gaps that still exist (e.g., species abundances), including valued harvest species like Arctic char (Salvelinus alpinus), walrus (Odobenus rosmarus), and seals, and importantly our poor understanding of the system in winter. Moving forward, we will collaborate with Inuit partners in Qikiqtarjuaq, NU, Canada, to improve this modeling tool by including Inuit knowledge. This tool thus serves as a starting point for collaborative discussions with Inuit partners and how its use can better inform local and regional decision-making regarding food security.

Assessment of the impact of polar bears on the grouping of pacific walruses at the Cape Vankarem rookery during the summer-autumn period in 2017–2021

The aim of this work is to assess the impact of polar bears (Ursus maritimus Phipps, 1774) on the distribution, abundance, and migration activity of Pacific walrus (Odobenus rosmarus divergens Illiger, 1815) on the coastal rookery Cape Vankarem (Chukotka Autonomous District) during the period from August to October 2017–2021.Also, based on the analysis of data on the number of walruses and bears on the rookery and analysis of photographs, we tried to assess the physical condition of predators, the degree of their attachment to the rookery, i. e. to determine how the age and sex composition of the bear group at the rookery changes during the development of walrus migration activity on the Cape Vankarem rookery. It has been established that: along with anthropogenic influence, polar bears are one of the main factors scaring walruses on the Cape Vankarem coastal rookery; immature bears spend significantly more time at the rookery than adult females with pups or adult males; the physical condition of the majority of bears is good, but the adult males are more frequently below average in fatness; while in the rookery, no food and space competition for food resources was observed between bears.

Social Transmission of Innovative Sound Production in Walruses (Odobenus rosmarus)

Social Transmission of Innovative Sound Production in Walruses (Odobenus rosmarus)

A Walrus (Odobenus rosmarus) at the North Pole

A Walrus (Odobenus rosmarus) at the North Pole

Winners and losers in a warming Arctic: Potential habitat gain and loss for epibenthic invertebrates of the Chukchi and Bering Seas, 2008–2100

Our goal was to examine how the epibenthic invertebrate community in the Pacific Arctic Region might be affected by continued increases in ocean temperatures. We used epibenthic invertebrate catch and bottom temperature data collected on groundfish assessment and ecosystem surveys in the Bering and Chukchi seas from 2009 to 2018 to determine the “preferred” temperature of all taxa. We grouped taxa into five clusters according to their similarity in median temperature and temperature range. We then used an ensemble of eight climate models under Representative Concentration Pathway 8.5 (RCP8.5) scenarios to project bottom temperature from present (2008) to mid-century (2050) and end of the century (2100). Based on these projections, we show how the amount and distribution of cluster-specific thermal habitat might change with ocean warming. We found that by mid-century there was a 50% decrease in thermal habitat for all clusters except for the most eurythermic cluster, and that thermal habitat contracted to the north. By the end of the century there was very little thermal habitat for all clusters, except the most eurythermic cluster, and habitat was further contracted to the north. The cold-water and stenothermic cluster, hypothesized to be the most vulnerable to ocean warming, had virtually no projected thermal habitat by the end of the century. These “losers” were primarily gastropods and the bivalve mussel Musculus sp. These taxa are some of the primary prey to the endangered Pacific walrus (Odobenus rosmarus), which is harvested as a food resource in native Alaskan communities. Bivalves are prey for commercial flatfish such as yellowfin sole (Limanda aspera) and Alaska plaice (Pleuronectes quadrituberculatus). By 2100 the most eurythermic cluster, hypothesized to be the least vulnerable to warming, had projected suitable thermal habitat throughout most of the Bering and Chukchi seas, except nearshore coastal regions. The most abundant species of these “winners” was the basketstar Gorgonocephalus cf. arcticus. The loss of thermal habitat for all but the “winners” could impact the species diversity of the Bering and Chukchi seas because the “winner” cluster accounted for only 26 taxa or 8% of all taxa observed. Although temperature is a key determinant of habitat, a full habitat and ecosystem model is needed to provide more detailed predictions. In addition, more laboratory studies of thermal acclimation potential of Arctic benthic invertebrates are needed. Our results provide the first indications that the epibenthic invertebrate community in the Bering and Chukchi seas, which supports marine mammals, seabirds and human communities, may be seriously impacted by future ocean warming.

Sexual dimorphism in the walrus mandible: comparative description and geometric morphometrics.

The modern walrus Odobenus rosmarus is characterized by marked sexual dimorphism, related to its polygynous behavior and the aggressive competition between males during the breeding season. Previous studies treated skeletal sexual dimorphism in walruses either qualitatively or with basic quantitative measurements. The present study combines a detailed qualitative comparison of male and female walrus mandibles with quantitative two-dimensional geometric morphometrics analysis (principal component analysis, Procrustes ANOVA and a linear discriminant analysis). In addition to identifying previously recognized sexually dimorphic features (e.g., convexity of the anterior margin of the mandible in adult males), our study finds new morphological differences between males and females, such as a relative dorsal expansion of the anterior part of the mandible and an accentuated concavity between the dorsal margin and the coronoid process in adult males. Both our qualitative comparisons and quantitative analyses demonstrate that sexual dimorphism as expressed in the mandible of extant walruses is statistically significant and that (variation in) mandibular morphology can be used as tool to attribute sex with a good degree of accuracy to isolated mandibles or skeletons lacking the cranium. Sexual dimorphism in walruses is directly related to their sexual behavior, characterized as aggressive in males and linked to a polygynous reproduction system. Indeed, the difference in size of the tusks between males and females but also the use of these during intraspecific fights, can reasonably account for this great mandibular morphological disparity between adult males and females, but also among different ontogenetic stages. Finally, the results obtained in the present study may serve as a starting point for assessing sexual dimorphism more in-depth and studying inter- and intraspecific variation in the mandibles of fossil walruses by identifying quantified size and shape mandibular features.

Applying landscape fragmentation analysis to icescape environments: potential impacts for the Pacific walrus (Odobenus rosmarus divergens)

Sea-ice cover across the Arctic has declined rapidly over the past several decades owing to amplified climate warming. The Pacific walrus (Odobenus rosmarus divergens) relies on sea-ice floes in the St. Lawrence Island (SLI) and Wainwright regions of the Bering and Chukchi seas surrounding Alaska as a platform for rest, feeding and reproduction. Lower concentrations of thick ice floes are generally associated with earlier seasonal fragmentation and shorter annual persistence of sea-ice cover, potentially affecting the life history of the Pacific walrus. In this study, 24 Landsat satellite images were classified into thick ice, thin ice or open water to assess sea-ice fragmentation over the spring-summer breakup period. Geospatial fragmentation analyses traditionally used in terrestrial landscapes were newly implemented in this study to characterize the icescape environment. Fragmentation of sea ice was assessed based on the Percent of Landscape, Number of Patches, Mean Area, Shape Index, Euclidean Nearest Neighbor and Edge Density. Results show that lower sea-ice concentrations in both the SLI and Wainwright regions were associated with smaller sea-ice floes. In the Bering Sea, lower sea-ice concentrations were also associated with increases in the number of ice floes, floe isolation and edge density. By contrast, lower sea-ice concentrations in the Chukchi Sea were associated with ice floes that were more circular in shape. The continuation of sea-ice decline with shifting icescape characteristics may result in walruses having to swim longer distances in the northern Bering Sea and adapt to use less-preferred, rounder ice floes in the Chukchi Sea.

Toxic and essential trace element concentrations in Pacific walrus (Odobenus rosmarus divergens) skeletal muscle varies by location and reproductive status

Toxic and essential trace element concentrations in Pacific walrus (Odobenus rosmarus divergens) skeletal muscle varies by location and reproductive status

PFAS and PBDEs in traditional subsistence foods from Sivuqaq, Alaska.

The Arctic is a hemispheric sink for both legacy and current use persistent organic pollutants (POPs). Once in the Arctic, POPs biomagnify in food webs, potentially reaching concentrations in high trophic level animals that pose a health concern for people who subsist on those animals. Indigenous Peoples of the Arctic may be highly exposed to POPs through their traditional diets. The objective of this study was to assess concentrations of polybrominated diphenyl ethers (PBDEs) and per- and polyfluoroalkyl substances (PFAS) in tissues of traditionally harvested foods from Sivuqaq (St. Lawrence Island), Alaska. Community health researchers identified volunteer households and local hunters to donate tissues from traditionally harvested animals. Target species included bowhead whale (Balaena mysticetus), Pacific walrus (Odobenus rosmarus), ringed seal (Pusa hispida), bearded seal (Erignathus barbatus), ribbon seal (Histriophoca fasciata), spotted seal (Phoca largha), and reindeer (Rangifer tarandus). PBDEs were frequently detected in all species and tissues. PBDE concentrations tended to be highest in lipid-rich tissues of seals. PFAS were infrequently detected and did not show obvious patterns among species or tissues. This and other studies demonstrate that POPs such as PBDEs are present in tissues of traditional food animals from Sivuqaq, as they are throughout the Arctic, and consumption of these animals likely contributes to exposure among Arctic Indigenous Peoples.