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At least 19 recordsLinked to original sources

PubMed2003

Feeding behaviour of free-ranging walruses with notes on apparent dextrality of flipper use.

BACKGROUND: Direct observations of underwater behaviour of free-living marine mammals are rare. This is particularly true for large and potentially dangerous species such as the walrus (Odobenus rosmarus). Walruses are highly specialised predators on benthic invertebrates - especially bivalves. The unique feeding niche of walruses has led to speculations as to their underwater foraging behaviour. Based on observations of walruses in captivity and signs of predation left on the sea floor by free-living walruses, various types of feeding behaviour have been suggested in the literature. In this study, however, the underwater feeding behaviour of wild adult male Atlantic walruses (O. r. rosmarus) is documented for the first time in their natural habitat by scuba-divers. The video recordings indicated a predisposition for use of the right front flipper during feeding. This tendency towards dextrality was explored further by examining a museum collection of extremities of walrus skeletons. RESULTS: During July and August 2001, twelve video-recordings of foraging adult male walruses were made in Young Sound (74 degrees 18 N; 20 degrees 15 V), Northeast Greenland. The recordings did not allow for differentiation among animals, however based on notes by the photographer at least five different individuals were involved. The walruses showed four different foraging behaviours; removing sediment by beating the right flipper, removing sediment by beating the left flipper, removing sediment by use of a water-jet from the mouth and rooting through sediment with the muzzle. There was a significant preference for using right flipper over left flipper during foraging. Measurements of the dimensions of forelimbs from 23 walrus skeletons revealed that the length of the right scapula, humerus, and ulna was significantly greater than that of the left, supporting our field observations of walruses showing a tendency of dextrality in flipper use. CONCLUSION: We suggest that the four feeding behaviours observed are typical of walruses in general, although walruses in other parts of their range may have evolved other types of feeding behaviour. While based on small sample sizes both the underwater observations and skeletal measurements suggest lateralized limb use, which is the first time this has been reported in a pinniped.

Animals↗

PubMed2000

Temporal and spatial trends of persistent organochlorines in Greenland walrus (Odobenus rosmarus rosmarus).

Persistent organochlorines [PCBs, DDT and chlordane related compounds, dieldrin, toxaphene, hexachlorocyclohexane (HCH), chlorobenzenes] were determined in blubber of Atlantic walrus (Odobenus rosmarus rosmarus) in 1978 and 1988 from the Avanersuaq (Thule) region of north-west Greenland and in 1989 from Ittoqqortoormiit (Scoresbysund) in east Greenland. Lowest concentrations of organochlorines (OCs) were found in the samples from the Avanersuaq region while much higher levels of all compounds, except HCH isomers and mono/dichlorobiphenyls (CB5/8), were observed in samples (all males) from Ittoqqortoormiit. Total PCBs (sigma PCB) averaged 246 ng/g (wet wt.) male walrus from Avanersuaq and 2860 ng/g in samples from Ittoqqortoormiit. DDT isomers showed the greatest difference between the two locations, 50 x for p,p'-DDE and 69 x higher for p,p'-DDT. Ittoqqortoormiit walrus showed the pattern of OCs characteristic of seal-eating animals although the consumption of other organisms cannot be ruled out. The higher levels of OCs in east Greenland compared to north-west Greenland animals were consistent with results for polar bears, seals and gulls from the same regions. Principal components analysis showed that the pattern of OCs in Ittoqqortoormiit walrus was very similar to that in walrus from Inukjuaq in east Hudson Bay, which have previously been reported to be seal eaters, and quite distinct from the Avanersuaq walrus. No significant differences in mean concentrations of any OCs were found between male walrus from 1978 and 1988. For females, there were significantly higher levels of CB5/8, trichlorobiphenyls, dieldrin, toxaphene and alpha HCH as well as sigma HCH but not for sigma PCBs or DDT compounds. The data for Greenland walrus from the 1970s and late 1980s provide a baseline for future trend monitoring in walrus.

Adipose Tissue↗

PubMed2003

Evaluation of a digestion assay and determination of sample size and tissue for the reliable detection of Trichinella larvae in walrus meat.

A digestion assay was validated for the detection of Trichinella larvae in walrus (Odobenus rosmarus) meat, and appropriate samples for testing were determined using tissues from infected walruses harvested for food. Examination of muscles from 3 walruses showed that the tongue consistently contained approximately 2-6 times more larvae than the pectoral and intercostal muscles. Comparison of numbers of larvae in the root, body, and apex of the tongue from 3 walruses failed to identify a predilection site within the tongue, but the apex was considered an optimal tissue because of the high larval density within the tongue and the ease of collection. All 31 spiked samples weighing 50 g each and containing between 0.1 and 0.4 larvae per gram (lpg) were correctly identified as infected, indicating that the sensitivity of this procedure is adequate for diagnostic use. A sample size of 10 g consistently detected larvae in 2 walrus tongues containing > or = 0.3 lpg (n = 40), and until additional data are available, sample sizes from individual walrus tongues should be a minimum of 10 g. This study provides the preliminary data that were used for the development of a food safety analytical protocol for the detection of Trichinella in walrus meat in arctic communities.

Animals↗

PubMed1995

Can seal eating explain elevated levels of PCBs and organochlorine pesticides in walrus blubber from eastern Hudson Bay (Canada)?

Walrus (Odobenus rosmarus) blubber samples from Inukjuak and Akulivik (East Hudson Bay), Foxe Basin (Igloolik and Hall Beach) and Loks Land (East Baffin Island) were analysed for PCB congeners (ortho and non-ortho substituted) and other persistent organochlorines (DDT, toxaphene, chlordanes, dieldrin, mirex), as well as chlorinated dioxins/furans, to document spatial trends in contaminants in Canadian Arctic marine biota. Samples from 19 of 53 individuals had concentrations of SigmaPCBs greater than 1000 ng g(-1) (wet wt); the remaining individuals had much lower concentrations (50-600 ng g(-1)). Highest concentrations were found in samples from Inukjuak where average concentrations in blubber of females (N = 9) were 1450 +/- 954 ng g(-1) toxaphene, 2750 +/- 1780 ng g(-1) SigmaCHLOR, 2160 +/- 925 ng g(-1) SigmaDDT and 4790 +/- 2380 ng g(-1) SigmaPCB. SigmaPCB and SigmaDDT concentrations greater than 1000 ng g(-1) were unexpected based on previous studies of walrus from Greenland and Alaska. Local contamination was ruled out because levels of all organochlorines were elevated in each animal from Inukjuak, and elevated levels were also found in animals from Akulivik and Loks Land. Walrus from Inukjuak had sigma13C and sigma15N values in muscle intermediate between those of ringed seals (Phoca hispida) and those of walrus from Akulivik with low organochlorine levels. There was a weak but significant correlation between and sigma15N and (log)SigmaPCB. The Inukjuak walrus also had higher proportions of highly chlorinated PCB congeners, and higher DDE/SigmaDDT ratios than walrus from Igloolik or Akulivik. The results suggest that the walrus with elevated organochlorines are feeding at a higher trophic level than those with low levels and are probably utilizing ringed seals for a portion of their diet.

Journal Article↗

PubMed1998

Population structure and gene flow of the Atlantic walrus (Odobenus rosmarus rosmarus) in the eastern Atlantic Arctic based on mitochondrial DNA and microsatellite variation.

The population structure of the Atlantic walrus, Odobenus rosmarus rosmarus, was studied using 11 polymorphic microsatellites and restriction fragment length polymorphism detected in the NADH-dehydrogenase ND1, ND2 and ND3/4 segments in mtDNA. A total of 105 walrus samples were analysed from northwest (NW) Greenland, east (E) Greenland, Svalbard and Franz Joseph Land. Two of the 10 haplotypes detected in the four samples were diagnostic for the NW Greenland sample, which implied that the group of walruses in this area is evolutionary distinct from walruses in the other three areas. One individual sampled in E Greenland exhibited a Pacific haplotype, which proved a connection between the Pacific walrus and walruses in eastern Greenland. The Franz Joseph Land, Svalbard and E Greenland samples shared the most common haplotype, indicating very little differentiation at the mtDNA level. Gene flow (Nm) estimates among the four areas indicated a very restricted exchange of female genes between NW Greenland and the more eastern Atlantic Arctic samples, and a closer relationship between the three samples composing the eastern Atlantic Arctic. The genetic variation at 11 polymorphic microsatellite loci grouped individuals into three populations, NW Greenland, E Greenland and a common Franz Joseph Land-Svalbard population, which were connected by moderate gene flow.

Animals↗

PubMed2000

A morbillivirus antibody survey of Atlantic walrus, narwhal and beluga in Canada.

A longitudinal serologic survey was conducted for morbillivirus antibodies in Atlantic walruses (Odobenus rosmarus rosmarus), narwhal (Monodon monoceros), and beluga (Delphinapterus leucas) from the Northwest Territories, Nunavut and the St. Lawrence estuary (Canada). Sixty-five of 131 (50%) walruses sampled between 1984 and 1993 had detectable morbillivirus neutralizing antibodies. Positive walrus were identified from four of five Arctic sampling sites, to as far back as 1984. Prevalence of morbillivirus neutralizing antibodies in walruses from Foxe Basin ranged from a high of 76% (n = 21) in 1993 to a low of 22% (n = 28) in 1984. Limitations in sample acquisition may have produced underestimates for the 1984 data. There are no reports of clinical morbillivirus infection in walruses. Our results are consistent with the hypothesis that a morbillivirus similar or identical to phocine distemper virus (PDV) has circulated among walrus populations of the eastern Canadian Arctic, at least since the early 1980s. No narwhal (n = 79) or beluga (n = 445) from Arctic waters were identified as having antibodies to dolphin morbilivirus (DMV) above the threshold serum dilution of log2 4. Also, none of the beach-cast cetacean carcasses (n = 28) from the Gulf of St. Lawrence and the St. Lawrence estuary were positive for antibodies to DMV. This indicates that Gulf of St. Lawrence, St. Lawrence estuary, and Arctic cetaceans either have not been exposed to DMV or an antigenically related morbillivirus, or are not susceptible to infection.

Animals↗

PubMed2004

A preliminary investigation on the infectivity of Trichinella larvae in traditional preparations of walrus meat.

This study evaluated the infectivity of Trichinella nativa in freshly frozen walrus meat and traditionally aged walrus meat (igunaq) associated with two human outbreaks of trichinellosis in the Canadian Arctic. Trichinella larvae recovered from walrus meat stored at -20 degrees C for up to 20 months remained infective for guinea pigs inoculated with 135 or 716 larval doses. However, none of the 4-5 and 10-month-old igunaq preparations contained infective T. nativa larvae as measured by bioassays using mice and guinea pigs at inoculation doses ranging from 6 to 500 larvae. This indicates that the degradation process that occurred in the field can be sufficient to either kill Trichinella larvae or render them non-infective for mice and guinea pigs. Further research is needed to evaluate the food safety risk of traditional walrus igunaq aged under different field conditions and storage times.

Animals↗

PubMed1986

Antibodies to marine caliciviruses in the Pacific walrus (Odobenus rosmarus divergens Illiger).

Sera from 155 Pacific walruses (Odobenus rosmarus divergens Illiger), sampled in the Chukchi Sea during the summer of 1983, were tested for serum neutralizing (SN) antibodies to six marine calicivirus serotypes. Serotypes tested included San Miguel sea lion virus (SMSV) types 1, 5, 8, and 10, previously isolated from northern fur seals (Callorhinus ursinus Linné) in the Bering Sea; walrus calicivirus (WCV), previously isolated from walrus feces collected off sea ice in the Chukchi Sea; and Tillamook calicivirus (TCV), a bovine isolate from Oregon of suspected marine origin. No antibodies were found to SMSV-1, SMSV-10, or TCV. Antibodies to SMSV-5 were found in two animals (titers 1:20 and 1:160); antibodies to SMSV-8 were found in four animals (all 1:20); and antibodies to WCV were found in one animal (titer 1:40). Antibodies to WCV have been found in the Pacific walrus previously; however, this represents the first report of antibodies to any of the SMSV serotypes in this marine mammal.

Animals↗

PubMed2006

Persistent organic pollutants in Alaskan ringed seal (Phoca hispida) and walrus (Odobenus rosmarus) blubber.

Since 1987, the Alaska Marine Mammal Tissue Archival Project (AMMTAP) has collected tissues from 18 marine mammal species. Specimens are archived in the National Institute of Standards and Technology's National Biomonitoring Specimen Bank (NIST-NBSB). AMMTAP has collected blubber, liver and/or kidney specimens from a number of ringed seals (Phoca hispida) from the areas near Nome and Barrow, Alaska and walruses (Odobenus rosmarus) from several locations in the Bering Sea. Thirty-three ringed seal and 15 walrus blubber samples from the NIST-NBSB were analyzed for persistent organic pollutants (POPs). The compounds determined included PCBs (28 congeners or congener groups), DDT and related compounds, hexachlorobenzene (HCB), hexachlorocyclohexane isomers (HCHs), chlordanes, dieldrin, and mirex. POP concentrations in ringed seal blubber were significantly higher in Barrow than in Nome when statistically accounting for the interaction of age and gender; HCB, however, was not statistically different between the two locations. Unlike males, POP concentrations and age were not significantly correlated in females probably as a result of lactational loss. POP concentrations in walrus blubber were lower than in ringed seal blubber for SigmaPCBs, chlordanes, and HCHs, but higher for dieldrin and mirex. POP concentrations in ringed seals and walrus from Alaska provide further evidence that the western Arctic tends to have lower or similar POP concentrations compared to the eastern Canadian Arctic.

Adipose Tissue↗

PubMed2006

Congener-specific accumulation and patterns of chlorinated and brominated contaminants in adult male walruses from Svalbard, Norway: indications for individual-specific prey selection.

Blubber samples from 17 adult, male walruses were sampled in eastern Svalbard and analyzed for chlorinated and brominated contaminants. A wide range of contaminants were detected, including PCBs (mean 2000; 95% range 1165-4005 ng/g lipid), DDE (mean 100: 95% range 50-310) ng/g lipid), chlordanes (mean 2500; 95% range 1347-5009) ng/g lipid, toxaphenes (mean 80; 95% range 51-132 ng/g lipid) and polybrominated diphenyl ethers (PBDEs) (mean 15 ng/g; 95% range 9-27 ng/g lipid). PCB and DDE levels were substantially lower than those of animals sampled 10 year earlier in this area, confirming a decreasing trend for these compounds in the Arctic. However, compared to other recently sampled marine mammals from Svalbard, walruses showed relatively high PCB and chlordane levels although they had lower levels of DDE, toxaphenes, and PBDEs, possibly due to species- and location-specific differences in exposure and metabolism. The range in contaminant levels found within the sample group was vast, despite the fact that the animals investigated were all adult males from the same location. The PCB pattern in highly contaminated animals was different from that in animals with low levels of contamination, with relatively more persistent PCBs in the highly contaminated group. This suggests that the more contaminated animals were feeding at higher trophic levels; possibly targeting seals in addition to mollusks as their prey. This suggestion was reinforced by the fatty acid profiles of the inner blubber layer of walruses with low versus high contaminant levels, which suggested different diets for the two groups.

Adipose Tissue↗

PubMed1979

Arctic trichinosis: two Alaskan outbreaks from walrus meat.

The arctic form of Trichinella spiralis that infects terrestrial and marine mammals is of importance in public health because persons living in arctic regions still depend on wild animals for economic subsistence. In 1975, an extended common-source epidemic of trichinosis attributed to consumption of walrus meat involved 29 persons in Barrow, Alaska. Of those persons eating this meat, 64% became ill, and the rate of infection of persons eating meat prepared with little or no cooking was four times as great as that of persons eating cooked meat. One year later a second outbreak occurred when a family ate partially cooked meat from an infected walrus. Clinical illness differed little from the disease acquired in temperature climates; however, only 70% had a positive bentonite flocculation titer, whereas 96% had eosinophilia. These epidemics of trichinosis are the first reported in Alaska to be associated with the consumption of walrus meat.

Alaska↗

PubMed2002

Underwater audiogram of a Pacific walrus (Odobenus rosmarus divergens) measured with narrow-band frequency-modulated signals.

The underwater hearing sensitivity of an 18-year-old male Pacific walrus was measured in a pool by using a go/no-go response paradigm and the up-down staircase method. Auditory sensitivity was measured using narrow-band, frequency-modulated signals (1500 ms duration) with center frequencies ranging from 0.125 to 15 kHz. The resulting underwater audiogram (50% detection thresholds) for this individual walrus shows the typical mammalian U-shape. Maximum sensitivity (67 dB re 1 microPa) occurred at 12 kHz. The range of best hearing (10 dB from the maximum sensitivity) was from 1 to 12 kHz. Sensitivity fell gradually below 1 kHz and dropped off sharply above 12 kHz. The animal showed a peculiar insensitivity for 2 kHz signals. His much higher sensitivity for 1.5- and 3-kHz signals indicated that this is a narrow-band phenomenon. Walrus hearing is relatively sensitive to low frequency sound, thus the species is likely to be susceptible to anthropogenic noise. The thresholds found during a small test with four frequencies with signal durations of 300 ms did not differ significantly from those obtained with signal durations of 1500 ms.

Animal Communication↗

PubMed1994

Neutralizing antibodies to phocine distemper virus in Atlantic walruses (Odobenus rosmarus rosmarus) from Arctic Canada.

The first evidence of phocine distemper virus (PDV) infection in Atlantic walruses (Odobenus rosmarus rosmarus) from Nottingham Island, Northwest Territories, Canada, is reported. Blood samples were collected from three male walruses killed by Inuit hunters in the fall of 1990. Differential virus neutralization test for each animal yielded higher titers against PDV than against other members of the Morbillivirus genus including canine distemper, peste des petits ruminants, rinderpest and measles viruses. Thus, PDV infection may be enzootic in walruses of the eastern Canadian Arctic.

Animals↗

PubMed1995

Micro-spatial variations of heavy metals in the teeth of walrus as determined by laser ablation ICP-MS: the potential for reconstructing a history of metal exposure.

This study explored the possibility of using laser ablation inductively-coupled plasma-mass spectroscopy to measure trace metals and other elements within the annual growth layers of the teeth of walrus harvested from the Canadian Arctic. Using sample ablation "footprints" of 125 microns diameter on transects across the exposed cross-sections of teeth, this technique detected Pb, Cu, Zn and Sr, but not Cd, in tooth cementum. The micro-spatial patterns of elements were consistent among different transects on the same tooth, and revealed subtle differences between animals of different ages. The youngest walrus in the sample (4 yr) contained higher concentrations of Pb and Cu than older animals in the growth layer deposited during the first year of life, while the oldest animal (33 yr) exhibited higher Pb and Zn than younger animals in the outer layer corresponding to the year 1988. The differences between animals and across annual layers may reflect both life history and metal exposure phenomena, including high amounts of metals transferred from mothers to pups in maternal milk. The ability to detect metals in a repeatable fashion within annual growth layers suggests that metal exposure histories accurate to within a year might be re-constructed for the life-times of long-lived animals, and that a series of such individual studies would allow exposure histories covering centuries to be quickly assembled. These data may suggest the most likely explanation for the currently high levels of some metals observed in certain Arctic marine mammals, i.e., natural phenomenon or anthropogenic contamination.

Age Factors↗

PubMed2004

New Calicivirus isolated from walrus.

The nucleotide sequence and genome organization of a new member of Caliciviridae was determined. Cell culture inoculated with fecal matter from walrus was used to recover fragments of a new virus by Suppression Subtractive Hybridization (SSH). The isolate was identified as a member of the Vesivirus genus of Caliciviridae and designated the name Walrus Calicivirus (WCV). Sets of PCR primers spanning the entire putative genome were designed using known sequences of other vesiviruses. The assembled genome was 8289 nucleotides (nt) long and shared no more than 87% identity with sequences of the other members of the genus Vesivirus. The largest open reading frame (ORF1) between positions 4-5646 encoded a polyprotein. ORF2, found at position 5652-7778, encoded a putative capsid protein. ORF3 overlapped ORF2 and encoded a small basic protein. Comparative analysis of multiple caliciviral capsid proteins was performed to propose a uniform capsid structural organization for this viral family.

Amino Acid Sequence↗

PubMed1989

Carnivora: the primary structure of the Pacific Walrus (Odobenus rosmarus divergens, Pinnipedia) hemoglobin.

The primary structure of the alpha- and beta-chains of the hemoglobin from the Pacific Walrus (Odobenus rosmarus divergens, Pinnipedia) is presented. Sequence analysis revealed only one hemoglobin component whereas two bands were found in polyacrylamide gel electrophoresis. The globin chains were separated by high-performance liquid chromatography and the sequences determined by automatic liquid- and gas-phase sequencing of the chains and their tryptic peptides. The alpha-chains show 20 and the beta-chains 12 exchanges compared to the corresponding human chains. In the alpha-chains one heme- and two alpha 1/beta 1-contacts were exchanged whereas in the beta-chains one alpha 1/beta 1-, one alpha 1/beta 2-and one heme-contact are substituted. Compared to Harbour Seal (Phoca vitulina) the Walrus hemoglobin shows 9 amino-acid replacements in the alpha-chains and 5 in the beta-chains. The relation between Pinnipedia and Arctoidea is discussed.

Amino Acid Sequence↗

PubMed2002

Atherosclerosis with multifocal myocardial infarction in a Pacific walrus (Odobenus rosmarus divergens Illiger).

A 25-yr-old male captive walrus (Odobenus rosmarus divergens Illiger) died after suffering from periods of inactivity, anorexia, and weight loss for 8 wk. Necropsy revealed prominent, generalized atherosclerosis of cardiac arteries with widespread chronic myocardial infarction. Severe disseminated myocardial fibrosis most likely resulted in insidious cardiac failure that was ultimately the cause of death. Bouts of abdominal pain and disseminated cutaneous ulcers that had been observed 3 and 4 days before death, respectively, were attributed to circulatory failure and thrombosis. The cause of the vascular lesions remains unknown. When compared with humans, atherosclerosis is rare in animals and has not been described in a walrus.

Aging↗

PubMed2002

Viral and bacterial serology of free-ranging Pacific walrus.

Serum or heparinized plasma samples were obtained between 1994 and 1996 from 20 male and 20 female adult free-ranging Pacific walrus (Odobenus rosmarus divergens) from St. Lawrence Island and Round Island, Alaska. Samples were screened for antibodies to some potentially pathogenic bacteria and viruses. No sample had detectable antibody to Brucella spp. Three of 40 (8%) had low antibody titers to Leptospira interrogans serovars. Phocine distemper virus antibodies were not detected. Serologic responses to one or more caliciviruses (San Miguel sea lion virus 12 or vesicular exanthema of swine serotypes E54, F55, G55, 1934B) were detected in 18% (seven of 40) walrus. Antibodies to one or more subtypes of influenza A virus (H10, N2, N3, N5, N6, N7) were detected in 21% (eight of 38). Periodic screening of free-ranging populations for exposure to infectious diseases has become an important component of bio-monitoring programs to facilitate understanding and detecting trends in marine mammal populations.

Alaska↗