Walrus Research Articles

Conservation and photogrammetry of subfossil Quaternary walrus (Odobenus rosmarus) from the Bay of Fundy, Canada

We describe a simple, inexpensive approach to the conservation and preservation of the subfossil cranium and tusks of a Quaternary (c. 2,900-12,800 years BP) walrus (Odobenus rosmarus) dredged from salt water. Ideally, wet specimens should be kept immersed in seawater until the treatment process is initiated. Regardless, it is critical that specimens not be permitted to dry out prior to desalination. Desalination was accomplished by gradually replacing sea water with fresh tap water, followed by controlled, slow drying over more than 530 days. Spalling was restricted to the tusks and occurred mainly between days 293-300, requiring surface consolidation with a dilute polyvinylacetate solution. The specimens were sufficiently stabilized for geology collections storage following the 591-day process. The use of photogrammetry to produce a 3D digital image of the partial walrus cranium with tusks permitted us to minimize the necessity of future handling and conservation and to preserve details of overall morphology and meristics useful for both research and public exhibition.

Marine mammal biodiversity and rare narwhal (Monodon monoceros) observations near northern Ellesmere Island, Canada

AbstractA climate‐driven decline of sea ice has increased international interest in understanding the ecology of seldom studied high‐Arctic regions projected to retain the last remnants of summer sea ice. Arctic marine mammals are vulnerable to future environmental change due to their high dependence on sea ice. We completed aerial surveys in August 2019 to document the occurrence and location of marine mammals within the recently designated Tuvaijuittuq Marine Protected Area which acts as a last refuge for ice‐associated species. We present photographic evidence of narwhals (Monodon monoceros), Atlantic walruses (Odobenus rosmarus), bearded seals (Erignathus barbatus), and ringed seals (Pusa hispida) in Archer Fjord, northern Ellesmere Island, Nunavut, Canada (81°14′–81°49′ N). We discuss these observations in the context of historical records and more recent opportunistic sightings from the region to support the hypothesis of an expansion north of the currently accepted range of narwhal. The diversity and number of observations of marine mammals in Archer Fjord is a striking contrast to the relative scarcity of the rest of the surveyed region, with very few observations of ringed seals throughout the more northerly study area. Our observations highlight opportunities to further explore high‐latitude areas that may host unique marine mammal biodiversity in the region, including narwhal.

Temporomandibular Joint Pathology of Wild Carnivores in the Western USA.

Skull specimens from: southern sea otter (Enhydra lutris nereis), Eastern Pacific harbor seal (Phoca vitulina), California sea lion (Zalophus californianus), northern fur seal (Callorhinus ursinus), walrus (Odobenus rosmarus), polar bear (Ursus maritimus), North American brown bear (Ursus arctos), American black bear (Ursus americanus), California mountain lion (Puma concolor couguar), California bobcat (Lynx rufus californicus), gray fox (Urocyon cinereoargenteus), kit fox (Vulpes macrotis), and gray wolf (Canis lupus) (n = 5,011) were macroscopically examined for dental and temporomandibular joint (TMJ) pathology. The presence of temporomandibular joint osteoarthritis (TMJ-OA) varied across species: 4.1% of southern sea otter, 34.5% of harbor seal, 85.5% of California sea lion, 20% of northern fur seal, 60.5% of walrus, 9.2% of polar bear, 13.2% of North American brown bear, 50% of American black bear, 20.9% of California mountain lion, 0% of California bobcat and gray fox, 6.3% of kit fox, and 11.6% of gray wolf specimens had lesions consistent with TMJ-OA. TMJ-OA was significantly more prevalent in males than females in walrus, North American brown bear, polar bear, American black bear, and California mountain lion (p < 0.001, p = 0.005, p = 0.005, p = 0.002, and p = 0.004, respectively). No other species showed a sex predilection. Adult specimens were significantly more affected with TMJ-OA than young adults in the harbor seal, fur seal, walrus (all p < 0.001), and kit fox (p = 0.001). Gray wolf and American black bear young adults were significantly (p = 0.047 and p < 0.001) more affected by TMJ-OA than adults. Of the 13 species analyzed, only three species, namely the harbor seal, northern fur seal, and polar bear, had a significant increase in the prevalence of TMJ-OA if their teeth had attrition and abrasion (p < 0.001, p < 0.001, and p = 0.033, respectively). TMJ-OA can lead to morbidity and mortality in wild animals, but its etiology is not yet fully understood.

Novel herpesvirus discovered in walrus liver.

A walrus (Odobenus rosmarus) born in an aquarium and hand-reared in Japan died at the age of 11months. The affected animal showed fever and anorexia and had high levels of AST and ALT. Necropsy showed multiple necroses in the liver and adrenal glands and histological examination revealed necrotic lesions of the liver and adrenal cortex, both of which contained intranuclear inclusions. Electron microscopic analysis of the liver sample showed herpesvirus-like particles. High-throughput sequencing analysis of the liver sample and phylogenetic analysis of herpesvirus polymerase genes identified a new virus, Walrus alphaherpesvirus 1 (WaHV-1), which belonged to the subfamily Alphaherpesvirinae and had high homology with Phocid alphaherpesvirus 1. Phylogenetic analysis of the UL30 gene encoding glycoprotein B revealed that WaHV-1 was closely related to a cluster of phocid herpesviruses, including one that caused high mortality rates in harbor seals during past outbreaks. The mother walrus of the dead animal showed evidence of herpesvirus infection in the past and potentially harbored WaHV-1. As a result of hand-rearing, the dead animal might have acquired WaHV-1 from its infected mother and succumbed to WaHV-1 due to lack of maternal IgG, including those that could neutralize WaHV-1.

Distribution and habitat characteristics of pinnipeds and polar bears in the Svalbard Archipelago, 2005–2018

This study presents comprehensive mapping of the current distribution of pinnipeds and polar bears (Ursus maritimus) around Svalbard based on a regional marine mammal sightings programme and explores time-trends (2005–2018). Walruses (Odobenus rosmarus) were observed with high frequency and in high numbers around previously identified haul-out sites. At-sea walruses were seen close to the coast in shallow waters. Ringed seals (Pusa hispida) were observed in coastal areas throughout Svalbard, often in association with tidewater glacier fronts. There was no increase in the mean latitude for ringed seal observations, but there was an increased frequency of observations at around 82°N, which reflects their following a northward shift in the ice edge during summer foraging trips. Bearded seals (Erignathus barbatus) were observed frequently in north-western Spitsbergen and shared many habitat features with ringed seals. There was a slight increase in the mean latitude of bearded seal observations and a decreased frequency of observation in the southern parts of the archipelago, suggesting that this species might be shifting its distribution. Harbour seal (Phoca vitulina) observations within fjords have increased, likely as a consequence of increased inflow of Atlantic water into west coast fjords. Harp seals (Pagophilus groenlandicus) were observed with high frequency north of Svalbard. Hooded seals (Cystophora cristata) were observed only rarely. Polar bears were reported most frequently, undoubtedly as a result of an effort bias favouring this species. In spite of biases, citizen-based observations are useful for assessing broad distributional patterns of marine mammals through time.

Walrus teeth as biomonitors of trace elements in Arctic marine ecosystems

Effective biomonitoring requires an understanding of the factors driving concentrations of the substances or compounds of interest in the tissues of studied organisms. Biomonitoring of trace elements, and heavy metals in particular, has been the focus of much research; however, the complex roles many trace elements play in animal and plant tissues can make it difficult to disentangle environmental signals from physiology. This study examined the concentrations of 15 trace elements in the teeth of 122 Pacific walruses (Odobenus rosmarus divergens) to investigate the potential for walrus teeth as biomonitors of trace elements in Arctic ecosystems. Elemental concentrations were measured across cementum growth layer groups (GLGs), thereby reconstructing a lifetime history of element concentrations for each walrus. The locations of GLGs were used to divide trace element time series into individual years, allowing each GLG to be associated with an animal age and a calendar year. The elements studied exhibited a great deal of complexity, reflecting the numerous factors responsible for generating tooth trace element concentrations. Generalized linear mixed models were used to investigate the importance of age and sex in explaining observed variation in trace element concentrations. Some elements exhibited clear physiological signals (particularly zinc, strontium, barium, and lead), and all elements except arsenic varied by age and/or sex. Pearson's correlations revealed that elements were more strongly correlated among calendar years than among individual walruses, and correlations of trace elements within individual walruses were generally inconsistent or weak. Plots of average elemental concentrations through time from 1945 to 2014 further supported the correlation analyses, with many elements exhibiting similar patterns across the ~70-year period. Together, these results indicate the importance of physiology in modulating tooth trace element concentrations in walrus tooth cementum, but suggest that many trace elements reflect a record of environmental exposure and dietary intake/uptake.

Variability of Lipids and Fatty Acids in Pacific Walrus Blubber

The variability of lipid content and fatty acid (FA) composition across blubber depth and body sites are important considerations for condition and diet studies of marine mammals. We investigated lipid and FA variability among inner and outer blubber layers, three body sites, four study years, and lactation status of adult female Pacific walruses (Odobenus rosmarus divergens) using blubber samples collected from subsistence-harvested walruses in spring 2007–2010. Percent lipid content did not differ between the inner and outer blubber layers at the rump, flank, or sternum of walruses. Although FA composition differed between the inner and outer blubber layers, the difference was consistent across body sites, and differences between layers within individual FAs were small (&amp;lt;2%). Lipid content at the sternum of lactating females was 6% higher than non-lactating females, consistent with known variation in body condition among these reproductive classes. Across study years, lipid content varied 18% and individual FAs varied 6%, likely reflecting population-level interannual variability in energy budgets and small differences in diet among years. Consistency in blubber lipid content across blubber depth and body sites and detectable variation in blubber lipid content among reproductive classes and years suggests the potential for lipid content to be a useful indicator of walrus body condition. In addition to information on condition, FA composition of blubber samples could potentially provide insights into changes in walrus diet that may be expected to occur from changes in their access to prey resources resulting from continued sea ice loss.

Genomic sex identification of ancient pinnipeds using the dog genome

Determining the proportion of males and females in zooarchaeological assemblages can be used to reconstruct the diversity and severity of past anthropogenic impacts on animal populations, and can also provide valuable biological insights into past animal life-histories, behaviour and demography, including the effects of environmental change. However, such inferences have often not been possible due to the fragmented nature of the zooarchaeological record and a lack of clear diagnostic skeletal markers. In this study, we test whether the dog (Canis lupus familiaris) nuclear genome is suitable for genetic sex identification in pinnipeds. We initially tested 72 contemporary ringed seal (Pusa hispida) genomes with known sex, using the proportion of X chromosome DNA reads to chromosome 1 DNA reads (i.e. chrX/chr1-ratio) to distinguish males from females. This method was found to be highly reliable, with the ratios clustering in two clearly distinguishable sex groups, allowing 69 of the 72 individuals to be correctly identified according to sex. Secondly, to determine the lower limit of DNA reads required for this method, a subset of the ringed seal genome data was randomly down-sampled. We found a lower threshold of as few as 5000 mapped DNA sequence reads required for reliable sex identification. Finally, applying this standard, sex identification was successfully carried out on a broad set of ancient pinniped samples, including walruses (Odobenus rosmarus), grey seals (Halichoerus grypus) and harp seals (Pagophilus groenlandicus). All three species showed clearly distinct male and female chrX/chr1 ratio groups, providing sex identification of 42–98% of the samples, depending on species and sample quality. The approach described in this study should aid in untangling the putative effects of human activities and environmental change on populations of pinnipeds and other animal species.

Marine mammal hotspots in the Greenland and Barents Seas

Environmental change and increasing levels of human activity are threats to marine mammals in the Arctic. Identifying marine mammal hotspots and areas of high species richness are essential to help guide management and conservation efforts. Herein, space use based on biotelemetric tracking devices deployed on 13 species (ringed sealPusa hispida, bearded sealErignathus barbatus, harbour sealPhoca vitulina, walrusOdobenus rosmarus, harp sealPagophilus groenlandicus, hooded sealCystophora cristata, polar bearUrsus maritimus, bowhead whaleBalaena mysticetus, narwhalMonodon monoceros, white whaleDelphinapterus leucas, blue whaleBalaenoptera musculus, fin whaleBalaenoptera physalusand humpback whaleMegaptera novaeangliae; total = 585 individuals) in the Greenland and northern Barents Seas between 2005 and 2018 is reported. Getis-OrdGi* hotspots were calculated for each species as well as all species combined, and areas of high species richness were identified for summer/autumn (Jun-Dec), winter/spring (Jan-May) and the entire year. The marginal ice zone (MIZ) of the Greenland Sea and northern Barents Sea, the waters surrounding the Svalbard Archipelago and a few Northeast Greenland coastal sites were identified as key marine mammal hotspots and areas of high species richness in this region. Individual hotspots identified areas important for most of the tagged animals, such as common resting, nursing, moulting and foraging areas. Location hotspots identified areas heavily used by segments of the tagged populations, including denning areas for polar bears and foraging areas. The hotspots identified herein are also important habitats for seabirds and fishes, and thus conservation and management measures targeting these regions would benefit multiple groups of Arctic animals.

Steroid hormones in Pacific walrus bones collected over three millennia indicate physiological responses to changes in estimated population size and the environment.

The Pacific walrus (Odobenus rosmarus divergens) is an iconic Arctic marine mammal and an important resource to many Alaska Natives. A decrease in sea ice habitat and unknown population numbers has led to concern of the long-term future health of the walrus population. There is currently no clear understanding of how walrus physiology might be affected by a changing Arctic ecosystem. In this study, steroid hormone concentrations (progesterone, testosterone, cortisol and estradiol) were analysed in walrus bones collected during archaeological [3585-200calendar years before present (BP)], historical [1880-2006 common era (CE)] and modern (2014-2016CE) time periods, representing ~ 3651years, to track changes in reproductive activity and cortisol concentrations (biomarker of stress) over time. Our results show that modern walrus samples have similar cortisol concentrations (median = 43.97 ± standard deviation 904.38ng/g lipid) to archaeological walruses (38.94 ± 296.17ng/g lipid, P = 0.75). Cortisol concentrations were weakly correlated with a 15-year average September Chukchi Sea ice cover (P = 0.002, 0.02, r 2 = 0.09, 0.04, for females and males, respectively), indicating a possible physiological resiliency to sea ice recession in the Arctic. All steroid hormones had significant negative correlations with mean walrus population estimates from 1960 to 2016 (P < 0.001). Progesterone in females and testosterone in males exhibited significant correlations with average September Chukchi Sea ice cover for years 1880-2016 (P < 0.001 for both, r2 = 0.34, 0.22, respectively). Modern walruses had significantly lower (P = < 0.001) reproductive hormone concentrations compared with historic walruses during times of rapid population increase, indicative of a population possibly at carrying capacity. This is the first study to apply bone as a tool to monitor long-term changes in hormones that may be associated with changes in walrus population size and sea ice cover.

Detection of steroid and thyroid hormones in mammalian teeth.

Endocrine tools can provide an avenue to better understand mammalian life histories and predict how individuals and populations may respond to environmental stressors; however, few options exist for studying long-term endocrine patterns in individual marine mammals. Here, we (i) determined whether hormones could be measured in teeth from four marine mammal species: narwhal (Monodon monoceros), beluga (Delphinapterus leucas), killer whale (Orcinus orca) and Atlantic walrus (Odobenus rosmarus rosmarus); (ii) validated commercially available enzyme immunoassay kits for use with tooth extracts; and (iii) conducted biological validations for each species to determine whether reproductive hormone concentrations in teeth correlated with age of sexual maturity. Tooth extracts from all species had measurable concentrations of progesterone, testosterone, 17β-estradiol, corticosterone, aldosterone and triiodothyronine (T3); however, cortisol was undetectable. Parallelism between the binding curves of assay kit standards and serially diluted pools of tooth extract for each species was observed for all measurable hormones. Slopes of accuracy tests ranged from 0.750 to 1.116, with r2 values ranging from 0.977 to 1.000, indicating acceptable accuracy. Biological validations were inconsistent with predictions for each species, with the exception of female killer whales (n = 2), which assumed higher progesterone and testosterone concentrations in mature individuals than immature individuals. Instead, we observed a decline in progesterone and testosterone concentrations from infancy through adulthood in narwhal (n = 1) and walruses (n = 2) and higher reproductive hormone concentrations in immature individuals than mature individuals in belugas (n = 8 and 10, respectively) and male killer whales (n = 1 and 2, respectively). While unexpected, this pattern has been observed in other taxa; however, further analytical and biological validations are necessary before this technique can be used to assess individual mammalian endocrine patterns.

The Case of the ‘Missing’ Arctic Bivalves and The Walrus: The Biggest [Overlooked] Clam Fishery on the Planet

Bivalve molluscs represent a significant proportion of the diet of both Atlantic and Pacific walrus (Odobenus rosmarus rosmarus and Odobenus rosmarus divergens, respectively) and are pivotal to benthic–pelagic coupling and carbonate cycling in the Arctic oceans. The latter is of particular relevance in a period of seasonal ice retreat, freshwater release into associated surface waters, decreasing water pH, and possible undersaturation of Arctic waters with respect to aragonite. Using population estimates and predation rates for the walruses on bivalve molluscs, a conservative estimate of bivalve consumption in the regions of active walruses foraging is 2.0–3.0 × 106 tonnes y–1—a tonnage comparable to the landings for the largest U.S. commercial fishery, the walleye pollock fishery in the eastern Bering Sea. Predation loss to other apex predators such as bearded seals is discounted. Using production:biomass ratios comparable to other high-latitude bivalves, a conservative estimate of bivalve standing stock required to support walrus populations is 0.4–3.0 × 107 tonnes. Whereas predominant clam prey species exhibit longevity in the 30+ y range, sampled populations in the Bering and Chukchi seas are dominated by small, often less than 1.0 cm individuals. Large clams are rare to absent in samples, suggesting either rapid turnover of the population with high predation balanced by high recruitment and/or a bias in sampling that discounts larger, more sparse individuals. Walrus grazing contributes up to 4.0–6.0 × 106 tonnes y–1 of carbonate to buffering of near-surface sediments in Artic regions. Accurate estimates of bivalve biomass and, thereby, the carbonate budget of Arctic shelf clam species, are critical to understanding the stability of associated continental shelf communities with continued warming of these high-latitude systems and their associated tendency toward aragonite undersaturation.

Atlantic walrus signal latitudinal differences in the long-term decline of sea ice-derived carbon to benthic fauna in the Canadian Arctic.

Climate change is altering the biogeochemical and physical characteristics of the Arctic marine environment, which impacts sea ice algal and phytoplankton bloom dynamics and the vertical transport of these carbon sources to benthic communities. Little is known about whether the contribution of sea ice-derived carbon to benthic fauna and nitrogen cycling has changed over multiple decades in concert with receding sea ice. We combined compound-specific stable isotope analysis of amino acids with highly branched isoprenoid diatom lipid biomarkers using archived (1982–2016) tissue of benthivorous Atlantic walrus to examine temporal trends of sea ice-derived carbon, nitrogen isotope baseline and trophic position of Atlantic walrus at high- and mid-latitudes in the Canadian Arctic. Associated with an 18% sea ice decline in the mid-Arctic, sea ice-derived carbon contribution to Atlantic walrus decreased by 75% suggesting a strong decoupling of sea ice-benthic habitats. By contrast, a nearly exclusive amount of sea ice-derived carbon was maintained in high-Arctic Atlantic walrus (98% in 1996 and 89% in 2006) despite a similar percentage in sea ice reduction. Nitrogen isotope baseline or the trophic position of Atlantic walrus did not change over time at either location. These findings indicate latitudinal differences in the restructuring of carbon energy sources used by Atlantic walrus and their benthic prey, and in turn a change in Arctic marine ecosystem functioning between sea ice–pelagic–benthic habitats.

Isolation, characterization, and ecotoxicological application of marine mammal skin fibroblast cultures.

Marine mammal cell cultures are a multifunctional instrument for acquiring knowledge about life in the world's oceans in physiological, biochemical, genetic, and ecotoxicological aspects. We succeeded in isolation, cultivation, and characterization of skin fibroblast cultures from five marine mammal species. The cells of the spotted seal (Phoca largha), the sea lion (Eumetopias jubatus), and the walrus (Odobenus rosmarus) are unpretentious to the isolation procedure. The sea otter (Enhydra lutris) fibroblasts should be isolated by trypsin disaggregation, while only mechanical disaggregation was suitable for the beluga whale (Delphinapterus leucas) cells. The cell growth parameters have been determined allowing us to find the optimal seeding density for continuous and effective cultivation. The effects of nonpathogenic algal extracts on proliferation, viability, and functional activity of marine mammal cells in vitro have been presented and discussed for the first time.

Evaluating tooth strontium and barium as indicators of weaning age in Pacific walruses.

Lactation length and weaning age provide important information about maternal investment, which can reflect the health and nutritional status of the mother, as well as broader reproductive strategies in mammals. Calcium‐normalized strontium (Sr) and barium (Ba) concentrations in the growth layers of mammalian teeth differ for nursing animals and those consuming non‐milk foods, thus can be used to estimate age‐at‐weaning. To date, this approach has been used only for terrestrial animals, and almost exclusively for primates.The goal of this study was to determine whether Sr and Ba concentrations in the cementum of Pacific walrus Odobenus rosmarus divergens teeth can be used to estimate weaning age. Teeth from 107 walruses were analysed using laser ablation inductively coupled plasma mass spectrometry, and calcium‐normalized 88Sr and 137Ba concentrations were quantified.For most walruses, both Sr and Ba concentrations exhibited rapid changes in early life. Ba concentrations matched closely with expected patterns in the published literature, rapidly declining from high to low concentrations (typically from ~10 ppm to ~5 ppm). In contrast, Sr exhibited a pattern opposite to that presented in studies of terrestrial mammals, appearing nearly identical to Ba (typically declining from ~400 ppm to ~200 ppm). To explain these findings, we present conceptual models of the factors generating weaning signals in Sr and Ba for terrestrial mammals, as well as a new, hypothetical model for walruses. Both a visual and mathematical approach to weaning age estimation indicated a median weaning age of walruses at the end of the second year of life (in the second dark layer of the tooth cementum), with many walruses estimated to have weaned in their third year of life, and a smaller group weaning in their fourth or fifth year. This is later than expected, given a published estimate of walrus weaning at 18–24 months.These results do not conclusively support the use of tooth Sr and Ba for estimating weaning age in walruses, and further research is warranted to better understand the drivers of the observed patterns of Ba and Sr accumulation in walrus teeth.

Endocrine profiling of reproductive status and evidence of pseudopregnancy in the Pacific walrus (Odobenus rosmarus divergens).

Endocrine profiling is an increasingly utilized tool for detecting pregnancies in wild populations of mammals. Given the difficulty in calculating reproductive rates of Pacific walruses (Odobenus rosmarus divergens) the use of endocrine techniques for determining pregnancy rates could be particularly useful for management of the population. The goals of this study were to 1) determine if progesterone and total estrogen concentrations in ovarian tissues of female walruses could be used to determine reproductive state and 2) determine if walruses undergo a functional postpartum estrus, as is seen in other pinnipeds. Ovaries were collected from female walruses (n = 13) hunted in subsistence hunts by Alaska Native communities. Females were categorized as postpartum, full-term pregnant, pregnant diapause or unbred. Total estrogen concentrations were greatest in unbred (n = 2) and pregnant (n = 2) females. Progesterone concentrations were also nominally larger in unbred (n = 2) than pregnant (n = 2) and postpartum (n = 9) animals. Small samples sizes precluded the use of statistical comparisons among groups. Corpora lutea tissue samples in this study did not reflect the presence of a postpartum estrus in the month of May as postpartum females yielded lower total estrogen concentrations than unbred or pregnant animals. Both unbred animals were in a state of pseudopregnancy, which has not been physiologically described for this species before. The progesterone profiles in late (59 ng/g) and early (140 ng/g) pregnancy were lower than expected and fell within the range of the postpartum females (36–210 ng/g), suggesting low production of the hormone by the corpus luteum during these phases of pregnancy. Profiling reproductive hormones in free-ranging walruses demonstrates that an endocrine approach may be a valuable tool for determining reproductive status of females, however increased sample sizes and time of year must be considered to accurately separate pregnant versus pseudopregnant individuals.

Resting and swimming metabolic rates in juvenile walruses (Odobenus rosmarus)

AbstractChanges in Arctic ice conditions have raised concerns regarding potential impacts on energy expenditure and food requirements of walruses. Modeling the repercussions of environmental changes requires accurate species‐specific measures of bioenergetic expenditures. This is particularly true for walruses, who have a unique anatomy and foraging ecology from other pinnipeds. This study measured resting metabolic rate (RMR) and subsurface swimming metabolism in two juvenile walruses over a 13‐month period. The walruses had relatively low RMR compared to studies of other young pinnipeds. RMR was greater for the male than the female, as expected given its larger size; the reverse was true on a mass‐specific basis. There was also considerable variability in RMR for each walrus during the year that could not be accounted for by changes in body mass. Metabolism while swimming was about twice RMR, and locomotor costs were higher than generally predicted for other marine mammals. The lower calculated swimming efficiency may reflect the fact that walruses are not “high velocity” pursuit predators. The estimates of metabolic expenditure obtained in this study for young walruses are invaluable for quantifying the energetic consequences of behavioral changes induced by environmental shifts in the wild.

Integrated study of benthic foraging resources for Atlantic walrus (Odobenus rosmarus rosmarus) in the Pechora Sea, south‐eastern Barents Sea

Abstract The Atlantic walrus, Odobenus rosmarus rosmarus, forms a herd of nearly 4,000 heads in the Pechora Sea (south‐eastern Barents Sea). The Near Threatened status of O. rosmarus rosmarus and the relative isolation of the Pechora Sea population, as well as the potential impacts of human activities in the area, make it important to characterize key habitats, including feeding grounds, in order to protect the species. The aim of the present study was to integrate multiple sources of environmental and biological data collected by satellite telemetry, remotely operated vehicle (ROV), and benthic grab sampling to examine the distribution and diversity of benthic foraging resources used by walrus in the Pechora Sea. Analysis of satellite telemetry data from seven males tagged on Vaigach Island helped to identify areas of high use by walruses near haulout sites on Matveev and Vaigach islands, and in between. Field data were collected from those feeding grounds in July 2016 using ROV video recordings and bottom grab sampling. Analysis of 19 grab stations revealed a heterogeneous macrobenthic community of 133 taxa with a mean biomass of 147.11 ± 7.35 g/m2. Bivalve molluscs, particularly Astarte borealis, Astarte montagui, and Ciliatocardium ciliatum, dominated the overall macrobenthic biomass, making up two‐thirds of the total. Analysis of 16 ROV video transects showed high occurrences of mobile benthic decapods (3.03 ± 2.74 ind./min) and provided the first direct evidence that areas actively used by walrus in the Pechora Sea overlap with the distribution of the non‐native omnivorous snow crab, Chionoecetes opilio. Integrating multiple data sources provides an early foundation for the kinds of ecosystem‐based approaches needed to improve Pechora Sea resource management and to underpin Russia’s nascent marine spatial planning initiatives. Factors that need to be considered in marine spatial planning include impacts on benthic feeding grounds from offshore oil and gas development and the spread of the snow crab.

DNAmetabarcoding of feces to infer summer diet of Pacific walruses

AbstractEnvironmental conditions in the Chukchi Sea are changing rapidly and may alter the abundance and distribution of marine species and their benthic prey. We used a metabarcoding approach to identify potentially important prey taxa from Pacific walrus (Odobenus rosmarus divergens) fecal samples (n= 87). Bivalvia was the most dominant class of prey (66% of all normalized counts) and occurred in 98% of the samples. Polychaeta and Gastropoda occurred in 70% and 62% of the samples, respectively. The remaining nine invertebrate classes comprised &lt;21% of all normalized counts. The common occurrence of these three prey classes is consistent with examinations of walrus stomach contents. Despite these consistencies, biases in the metabarcoding approach to determine diet from feces have been highlighted in other studies and require further study, in addition to biases that may have arisen from our opportunistic sampling. However, this noninvasive approach provides accurate identification of prey taxa from degraded samples and could yield much‐needed information on shifts in walrus diet in a rapidly changing Arctic.

Diagnosis and Management of Goiter in an Atlantic Walrus (Odobenus rosmarus rosmarus)

Diagnosis and Management of Goiter in an Atlantic Walrus (Odobenus rosmarus rosmarus)