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Øystein Wiig - One of the best experts on this subject based on the ideXlab platform.
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Genetic diversity of historical Atlantic walruses (Odobenus rosmarus rosmarus) from Bjornoya and Haoya (Tusenoyane), Svalbard, Norway
BMC research notes, 2016Co-Authors: Charlotte Lindqvist, Øystein Wiig, Christian Lydersen, Tilottama Roy, Kit M. Kovacs, Jon Aars, Lutz BachmannAbstract:Background The population size of Atlantic walruses (Odobenus rosmarus rosmarus) is depleted relative to historical abundance levels. In Svalbard, centuries of over-exploitation brought the walrus herds to the verge of extinction, and such bottlenecks may have caused loss of genetic variation. To address this for Svalbard walruses, mitochondrial haplotypes of historical walruses from two major haul-out sites, Bjornoya and Haoya, within the Archipelago were explored using bone samples from animals killed during the peak period of harvesting.
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Management of Atlantic walrus (Odobenus rosmarus rosmarus) in the arctic Atlantic
NAMMCO Scientific Publications, 2014Co-Authors: Øystein Wiig, Erik W. Born, Robert E. A. StewartAbstract:We review the management of Atlantic walruses ( Odobenus rosmarus rosmarus ) past and present in the four range states—Canada, Greenland, Norway and Russia—which have permanent populations of Atlantic walruses. Populations in all four countries have been depleted, although the extent of depletion is not well known. Inuit in Arctic Canada and Greenland hunt Atlantic walruses for subsistence while they have been protected at Svalbard (Norway) since 1952 and in the western Russian Arctic since 1956. Since the second half of the 20 th Century Canada and Greenland have increased protection of their walrus. Generally the number of walruses landed in Canada is governed by the number of hunters and/or people in the settlement and not by stock-specific quotas. Although quotas have been set in few communities, it is not known if they are adequate to prevent overhunting. A quota system for walrus hunting in Greenland began in 2006. The current control system is largely effective in ensuring the quotas are applied and that reporting is correct. Greenland currently sets quotas based on recommendations from scientific assessments using recent population estimates to allow population growth from a depleted population. A challenge with respect to managing walrus hunting remains the variable and sometimes high rates of lost animals. Since the 1960s changes in socio-economics in hunting areas of Arctic Canada and Greenland (and the use of snowmobiles instead of dog sleds in Canada) have led to a general decrease in interest in hunting of walruses and reduced harvest on walrus stocks in these countries. Although there is an active ongoing cooperation between Canada and Greenland scientists regarding assessments of shared populations of walruses currently there is no formal agreement between the two range states on co-management of shared stocks. Protection of walrus from other anthropogenic impacts generally focusses on large-scale industrial activity. The level of protection afforded to walrus habitat in many areas depends entirely on the rigor with which the Environmental Impact Assessments are conducted. Basic information on walrus such as numbers and stock discreteness is often lacking and sufficient lead-time is required to collect baseline data. Moreover, although most environmental protection legislation considers ‘cumulative impacts’, practical application remains problematic. The effectiveness of environmental protection regulations depends on industry compliance and the management authorities’ ability to enforce compliance. Because walrus are found in remote locations, enforcement remains a challenge. Increased human activity allowed by the current change in distribution and quality of arctic sea ice poses new threats to walrus if not well regulated. International agreements have varying importance for management within and among member states. Regulations governing international trade serve to identify illegally obtained products and to encourage range states to have a sustainable quota system. International cooperation in information sharing has had clear benefits for management of walruses in the past. The maintenance and expansion of these international efforts will improve the management of Atlantic walruses in the future.
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Evaluation of etorphine reversed by diprenorphine for the immobilisation of free-ranging Atlantic walrus ( Odobenus rosmarus rosmarus L.)
NAMMCO Scientific Publications, 2014Co-Authors: Mario Acquarone, Erik W. Born, David Griffiths, Lars Øyvind Knutsen, Øystein Wiig, Ian GjertzAbstract:To date no problem-free method exists for the immobilisation of free‑ranging walruses ( Odobenus rosmarus ). In the period 1989-2001, 69 immobilisations with etorphine HCl were performed by remote darting of 41 individual free-ranging adult Atlantic walruses ( O. r. rosmarus ), with body masses 633 ‑ 1883 kg, as a rerequisite for the attachment of radio tracking and dive recording instruments, and for studies of metabolism. Ten individuals were immobilised several times. We present data on these 69 immobilisations and evaluate the method. Full immobilisation was achieved in 58 cases (84 %). The animals were insufficiently restrained in 6 cases (9 %) and 5 animals died (7 %) following the immobilisation. The animals were fully immobilised and approachable after 5 min (n = 38, range = 1.9 ‑ 12.4 min, SD = 2.2) with a dose of etorphine of 6.1 μg/kg (range 2.4 ‑ 12.6 μg /kg, SD = 2.4). Induction time was negatively correlated with the dosage of etorphine. Etorphine-induced apnoea lasted 13.7 min (n = 36, range 17.0 ‑ 26.7 min, SD = 5.1) and was reversed by multiple doses of the antagonist diprenorphine HCl. The first dose of antagonist of 12.2 mg (n = 39, range 6.0 ‑ 21.0 mg, SD = 3.5) was administered 8.4 min (n = 38, range 4.7 ‑ 18.0 min, SD = 2.8) after injection of the agonist. The total dose of diprenorphine per animal ranged between 7.7 and 41.7 μg/kg (n = 31, mean = 17.2 μg/kg, SD = 7.5). For some animals blood pH values were measured following the apnoea and reached low levels (min pH 6.8). For animals that were immobilised several times there were no indications of changed sensitivity to etorphine as reflected in unchanged induction times. Mortalities could neither be related to the doses of agonist and antagonist, nor to the times of administration of the drugs. From this (n = 69) and other (n = 103) studies involving etorphine immobilisation of walruses (both Atlantic and Pacific) the overall success rate is 83 % (8 % casualty rate). We conclude that the combination etorphine‑ diprenorphine is suitable for both single and multiple immobilisations of walruses provided that (a) a casualty rate of 7-8% is acceptable (b) the antagonist diprenorphine is administered fast and well into a tissue with good blood irrigation, and (c) the animal is promptly intubated endotracheally to facilitate the restoration of breathing after drug-induced apnoea.
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Genetic signals of historic and recent migration between sub-populations of Atlantic walrus Odobenus rosmarus rosmarus west and east of Greenland
Endangered Species Research, 2009Co-Authors: Liselotte Wesley Andersen, Øystein Wiig, Ian Gjertz, E.w. Born, D. W. Doidge, R.s. WaplesAbstract:Defining sub-populations and determining migration rates between them is crucial for sound management and conservation. This also applies to the Atlantic walrus Odobenus rosmarus rosmarus, which is still exploited although population levels are low in some cases and information on abundance is lacking in others. Analysis of muscle and skin tissues using 11 nuclear microsatellite markers from a total of 297 Atlantic walruses from the Hudson Strait across W, NW and E Greenland to Svalbard and Franz Josef Land was undertaken to determine the number of sub-populations, their ancestral origin and the contemporary rates and directions of migration (gene flow) between the var- ious areas. The study indicated the existence of 5 sub-populations in the Hudson Strait, W Greenland, NW Greenland, E Greenland and Franz Josef Land-Svalbard. Identification of the Hudson Strait sub- population was novel; although differences between animals here and in W Greenland were small, they were statistically significant and indicated that walruses in the Hudson Strait could be a popu- lation source for walruses for the W Greenland sub-population. The direction of migration (Hudson Strait to W Greenland) suggested a genetic signal from a historical large-scale counter-clockwise perennial migration pattern in the Baffin Bay region. The study provides essential information on population sub-structuring that is a prerequisite for management of Atlantic walruses at sustainable levels.
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The Laptev Sea walrus Odobenus rosmarus laptevi: an enigma revisited
Zoologica Scripta, 2009Co-Authors: Charlotte Lindqvist, Erik W. Born, Christian Lydersen, Kit M. Kovacs, Lutz Bachmann, Liselotte Wesley Andersen, Ulfur Arnason, Alexei V. Abramov, Øystein WiigAbstract:The walrus (Odobenus rosmarus) is in some current systematic schemes divided into three subspecies: O. r. rosmarus in the North Atlantic, O. r. divergens in the North Pacific and O. r. laptevi in the Laptev Sea. These three subspecies have been described as differing in body size, but the taxonomic status of O. r. laptevi is disputed. The current study applies molecular and morphometric methods to assess the taxonomic status of O. r. laptevi and to analyse the systematic and phylogeographic relationships between the three purported walrus subspecies. Tusk length and tusk circumference were measured from the few skulls available of O. r. laptevi, and the obtained values were within the ranges reported for Pacific walruses. Thus, morphologically, subspecies status for O. r. laptevi is not supported according to the Amadon Mayr '75% rule'. Phylogenetic analyses and haplotype networks based on mitochondrial nucleotide sequence data of NADH dehydrogenase 1, 16S rRNA, cytochrome oxidase I and the D-loop of the control region of the historic O. r. laptevi bone material and contemporary O. r. rosmarus and O. r. divergens showed that the Laptev Sea walrus groups with individuals from the North Pacific. Thus, the mitochondrial sequence data do not support the recognition of three walrus subspecies as reciprocally monophyletic evolutionary units with independent evolutionary histories. Only O. r. rosmarus and O. r. divergens meet this criterion with the present sampling. Accordingly, we recommend that Odobenus r. laptevi be abandoned and the Laptev walrus instead be recognized as the westernmost population of the Pacific walrus, Odobenus r. divergens. However, further research is recommended to assess whether the Laptev walrus could be considered as a significant unit in terms of conservation and management, since it is unique in several ecological parameters. (Less)
E.w. Born - One of the best experts on this subject based on the ideXlab platform.
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Genetic signals of historic and recent migration between sub-populations of Atlantic walrus Odobenus rosmarus rosmarus west and east of Greenland
Endangered Species Research, 2009Co-Authors: Liselotte Wesley Andersen, Øystein Wiig, Ian Gjertz, E.w. Born, D. W. Doidge, R.s. WaplesAbstract:Defining sub-populations and determining migration rates between them is crucial for sound management and conservation. This also applies to the Atlantic walrus Odobenus rosmarus rosmarus, which is still exploited although population levels are low in some cases and information on abundance is lacking in others. Analysis of muscle and skin tissues using 11 nuclear microsatellite markers from a total of 297 Atlantic walruses from the Hudson Strait across W, NW and E Greenland to Svalbard and Franz Josef Land was undertaken to determine the number of sub-populations, their ancestral origin and the contemporary rates and directions of migration (gene flow) between the var- ious areas. The study indicated the existence of 5 sub-populations in the Hudson Strait, W Greenland, NW Greenland, E Greenland and Franz Josef Land-Svalbard. Identification of the Hudson Strait sub- population was novel; although differences between animals here and in W Greenland were small, they were statistically significant and indicated that walruses in the Hudson Strait could be a popu- lation source for walruses for the W Greenland sub-population. The direction of migration (Hudson Strait to W Greenland) suggested a genetic signal from a historical large-scale counter-clockwise perennial migration pattern in the Baffin Bay region. The study provides essential information on population sub-structuring that is a prerequisite for management of Atlantic walruses at sustainable levels.
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REPRODUCTION IN MALE ATLANTIC WALRUSES (Odobenus rosmarus rosmarus) FROM THE NORTH WATER (N BAFFIN BAY)
Marine Mammal Science, 2003Co-Authors: E.w. BornAbstract:Age at sexual maturity and timing of the mating season were determined in male Atlantic walruses (Odobenus rosmarus rosmarus, L.) from the “North Water” subpopulation in northern Baffin Bay. Testes and epididymides of 174 male walruses (between 0 and 30 yr old) from NW Greenland (1987–1990) were studied macroscopically and a subset of 57 specimens was analyzed microscopically. In physically mature bulls (i.e., ≥12 yr old), sperm or apparently ripe spermatids were found between 9 November and 12 July. In younger walruses these signs of fertility were found in a few specimens (7–11 yr old) collected between 9 January and 28 May. The mating season seems to peak in January—April. The youngest sexually mature individual was 7 yr old and the oldest apparently immature individual was 13 yr old. Average age of sexual maturity was 10.9 yr (95% C.I.: 9–6–12.2 yr) and all were sexually mature by the time they were 14 yr old. The non-spermiogenetic testes and epididymides showed accelerated growth between about the 5–6th and about the 12–15th year of life, indicating that sexual maturation occurs during these years. The length of the baculum increased gradually until about 12–15 yr of age, when physical maturity was reached.
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Investigation of the Stock Structure of Atlantic Walrus ( Odobenus rosmarus rosmarus ) in Canada and Greenland Using Dental Pb Isotopes Derived from Local Geochemical Environments
ARCTIC, 2003Co-Authors: P. M. Outridge, Robert E. A. Stewart, W.j. Davis, E.w. BornAbstract:The chemical composition of animal tissues such as teeth appears to reflect an individual's exposure to its geochemical environment. In this study, the lead (Pb) isotope composition of dental cementum was used to investigate the stock structure of Atlantic walrus ( Odobenus rosmarus rosmarus ) in the Canadian Arctic and Greenland. The 12 communities providing walrus samples for this study represent most of the Canadian and Greenlandic villages where walrus still form an important part of the traditional Inuit diet. Significant differences between locations in mean Pb isotope ratios and the limited overlap of the ranges of values indicate that each village harvested walrus herds that exploited substantially different geological/geographical habitats. This geographic segregation based on isotopic signatures suggests that most walrus stocks (i.e., the groups of walrus that interact with hunters at each community) are more localized in their range than previously thought. 208Pb/207Pb and 208Pb/204Pb were the most important stock discriminators, reflecting the influence of local geological Th/U composition (i.e., 208Pb) on Pb isotope composition in walrus teeth. 204Pb-based isotope ratios in walrus were consistently higher (more radiogenic) and more homogeneous than those in regional terrestrial bedrock, a difference probably due to selective leaching of radiogenic Pb from mineral phases into seawater and mixing during weathering and transport. Dental Pb isotope signatures may have widespread application to stock discrimination of other coastal marine mammal species.
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Reproduction in female Atlantic walruses ( Odobenus rosmarus rosmarus ) from north-west Greenland
Journal of Zoology, 2001Co-Authors: E.w. BornAbstract:The reproductive tracts of 152 female Atlantic walruses Odobenus rosmarus rosmarus were analysed. The material was collected between 19 January and 19 November in 1977–78 ( n = 44) and 1988–91 ( n = 108) from the subsistence hunt by Inuit in north-west Greenland (i.e. in the eastern parts of the North Water polynya in northern Baffin Bay). Seventy-six per cent of the walruses were sexually mature. Oestrus females ( n = 23) were found between 19 January and 25 June. Based upon ovarian anatomy, females may ovulate several times during oestrus but ovarian anatomy could not be used to determine if an individual was pregnant. The youngest female that had given birth was 5 years old, indicating that some female Atlantic walruses become sexually mature at 4 years of age. The oldest immature female was 8 years old, and the oldest animal that ovulated for the first time was 11 years. Age-related growth in the reproductive tract indicated that sexual maturity was reached between 6 and 8 years of age. Based on reproductive history of 93 individuals (0–12 years old) the average age of attainment of sexual maturity (i.e. first ovulation) was 6.1 years (95% CI: 5.2–7.1 years). Of 81 mature females collected during May–November, 34.6% were pregnant, 43.2% postpartum and 22.2% inactive. These proportions did not differ from a model assuming a triennial reproductive cycle. Growth in foetal length and mass with time indicated that implantation occurred between 29 June and 11 July or between 26 June and 5 July, respectively. Mean birth date based on observations of 28 newborns was 20 June (range 4 February–11 November).
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Temporal and spatial trends of persistent organochlorines in Greenland walrus (Odobenus rosmarus rosmarus).
The Science of the total environment, 2000Co-Authors: D C Muir, E.w. Born, K Koczansky, G A SternAbstract: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.
Christian Lydersen - One of the best experts on this subject based on the ideXlab platform.
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Walrus: Odobenus rosmarus
Encyclopedia of Marine Mammals, 2018Co-Authors: Christian LydersenAbstract:Summary Modern walruses belong to a single species, within their own Family—Odobenidae. There are two recognized subspecies, the Pacific walrus (Odobenus rosmarus divergens) and the Atlantic walrus (O. r. rosmarus). This large, tusked pinniped is a benthic feeder that consumes primarily bivalve mollusk prey in shallow waters over continental shelves in the Arctic. Walruses are an important cultural and subsistence resource for local people in some Arctic regions. Overharvest has induced population reductions periodically in many areas. However, climate change induced sea ice losses likely represent the most serious threat to this species currently. The Pacific walrus has recently declined by 50%, resulting in an IUCN classification of the species as Vulnerable.
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SHORT DURATION IMMOBILIZATION OF ATLANTIC WALRUS ( Odobenus rosmarus rosmarus) WITH ETORPHINE, AND REVERSAL WITH NALTREXONE.
Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 2017Co-Authors: Rolf-arne Ølberg, Kit M. Kovacs, Mads F. Bertelsen, Varvara Semenova, Christian LydersenAbstract:Abstract Forty adult, male Atlantic walruses (Odobenus rosmarus rosmarus) were successfully immobilized for the attachment of global positioning system loggers on their tusks and collection of various biological samples. A standard dose of 7.8 mg etorphine was used for each animal, regardless of body size. All animals were reversed with an iv or im injection of 250 mg naltrexone, immediately after tag attachment. Twenty-seven of the animals were intubated and ventilated with 100% oxygen during the recovery period. The induction time was, on average, 4 min 51 sec ± 1 min 46 sec. Several animals had venous pH, and Pco2 levels that indicated severe acidosis and hypercarbia. All animals recovered within an average of 5 min 16 sec ± 2 min 47 sec after reversal. The total time from darting to recovery was 15 min 23 sec ± 3 min 33 sec. The use of naltrexone is recommended for reversal of etorphine immobilization in adult, male walruses, and the use of positive-pressure ventilation with oxygen is highly encouraged.
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Genetic diversity of historical Atlantic walruses (Odobenus rosmarus rosmarus) from Bjornoya and Haoya (Tusenoyane), Svalbard, Norway
BMC research notes, 2016Co-Authors: Charlotte Lindqvist, Øystein Wiig, Christian Lydersen, Tilottama Roy, Kit M. Kovacs, Jon Aars, Lutz BachmannAbstract:Background The population size of Atlantic walruses (Odobenus rosmarus rosmarus) is depleted relative to historical abundance levels. In Svalbard, centuries of over-exploitation brought the walrus herds to the verge of extinction, and such bottlenecks may have caused loss of genetic variation. To address this for Svalbard walruses, mitochondrial haplotypes of historical walruses from two major haul-out sites, Bjornoya and Haoya, within the Archipelago were explored using bone samples from animals killed during the peak period of harvesting.
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Year-round haul-out behaviour of male walruses Odobenus rosmarus in the Northern Barents Sea
Marine Ecology Progress Series, 2015Co-Authors: Charmain D. Hamilton, Kit M. Kovacs, Christian LydersenAbstract:Haul-out behaviour is a central component in the life history of pinnipeds; seasonal patterns in this behaviour reveal insights into annual energy budgets and basic biology. In this study, custom-designed satellite-relay data loggers were deployed on 17 male walruses Odobenus rosmarus in Svalbard, Norway. Individual animals transmitted data for a mean ± SD of 255 ± 132 d (range = 54�471 d), performing on average 110 ± 65 haul-out events (range = 30�247 events); the data records for 5 animals were longer than 1 yr. Clear seasonal patterns occurred in the percent- age of time hauled out and average haul-out duration; both variables reached maxima in summer and minima in winter. Time between haul-out events reached a maximum during the breeding season in winter. The walruses moved away from shore-based haul-out sites and onto sea ice in November and December, and returned to land again in June. Analyses using generalized addi- tive mixed models and Cox proportional hazard models demonstrated that wind chill and time in the water prior to a haul-out event had the largest impacts on haul-out probability and duration, although wind chill had little impact during the summer when temperatures were not challenging, and also had reduced influence during the breeding period. Long periods at sea were followed by long periods hauled out, resulting in a relatively constant proportion of time spent hauled out over time scales of weeks. Our results indicate the importance of breeding in dictating male haul-out patterns during winter, and provide a baseline to assess impacts of future climate change.
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serum chemistry reference values in free ranging north atlantic male walruses Odobenus rosmarus rosmarus from the svalbard archipelago
Veterinary Clinical Pathology, 2009Co-Authors: Morten Tryland, Christian Lydersen, Kit M. Kovacs, Stein Istre ThoresenAbstract:Background: Information regarding health and disease is limited for walruses, a keystone species in arctic marine ecosystems. Serum chemistry analysis is a useful clinical tool for the health assessment of walruses, but only a few captive Pacific walruses have been evaluated. Objectives: The aim of this study was to determine serum chemistry reference values for free-ranging male Atlantic walruses (Odobenus rosmarus rosmarus) on Svalbard and to assess potential differences in animals with low and high tissue levels of organic pollutants. Methods: Blood samples were collected from 17 wild, adult, male Atlantic walruses chemically immobilized with etorphine at eastern Svalbard (Norway). Serum was obtained for routine biochemical analysis as well as nonesterified free fatty acids (NEFA) and cortisol tests. Serum protein concentration was also measured by agarose gel electrophoresis. Results: Reference values (ranges) included alanine aminotransferase (12–51 U/L), aspartate aminotransferase (54–137 U/L), alkaline phosphatase (42–243 U/L), creatine kinase (32–506 U/L), lactate dehydrogenase (480–1322 U/L), amylase (0–23 U/L), lipase (68–298 U/L), total protein (68–91 g/L), albumin (25.3–34.8 g/L), creatinine (84–137 μmol/L), urea (8.2–19.9 mmol/L), bilirubin (0–4 μmol/L), cholesterol (4.4–7.3 mmol/L), NEFA (0.1–0.4 mmol/L), triglycerides (0.6–2.2 mmol/L), calcium (2.0–2.7 mmol/L), phosphorus (1.7–2.8 mmol/L), sodium (147–162 mmol/L), potassium (4.7–7.4 mmol/L), chloride (102–115 mmol/L), and cortisol (<28–214 nmol/L). Walruses exposed to high levels of organic pollutants (n=6) had significantly lower (P=.022) phosphorus concentration than those with low levels of pollutants (n=6). Conclusions: The clinical chemistry reference values determined in this study can serve as baseline data for future health-related studies of walruses in a changing Arctic and may also be helpful for health evaluations of walruses in captivity. Impacts of the exposure of marine mammals to organic pollutants should be further investigated.
Ian Gjertz - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of etorphine reversed by diprenorphine for the immobilisation of free-ranging Atlantic walrus ( Odobenus rosmarus rosmarus L.)
NAMMCO Scientific Publications, 2014Co-Authors: Mario Acquarone, Erik W. Born, David Griffiths, Lars Øyvind Knutsen, Øystein Wiig, Ian GjertzAbstract:To date no problem-free method exists for the immobilisation of free‑ranging walruses ( Odobenus rosmarus ). In the period 1989-2001, 69 immobilisations with etorphine HCl were performed by remote darting of 41 individual free-ranging adult Atlantic walruses ( O. r. rosmarus ), with body masses 633 ‑ 1883 kg, as a rerequisite for the attachment of radio tracking and dive recording instruments, and for studies of metabolism. Ten individuals were immobilised several times. We present data on these 69 immobilisations and evaluate the method. Full immobilisation was achieved in 58 cases (84 %). The animals were insufficiently restrained in 6 cases (9 %) and 5 animals died (7 %) following the immobilisation. The animals were fully immobilised and approachable after 5 min (n = 38, range = 1.9 ‑ 12.4 min, SD = 2.2) with a dose of etorphine of 6.1 μg/kg (range 2.4 ‑ 12.6 μg /kg, SD = 2.4). Induction time was negatively correlated with the dosage of etorphine. Etorphine-induced apnoea lasted 13.7 min (n = 36, range 17.0 ‑ 26.7 min, SD = 5.1) and was reversed by multiple doses of the antagonist diprenorphine HCl. The first dose of antagonist of 12.2 mg (n = 39, range 6.0 ‑ 21.0 mg, SD = 3.5) was administered 8.4 min (n = 38, range 4.7 ‑ 18.0 min, SD = 2.8) after injection of the agonist. The total dose of diprenorphine per animal ranged between 7.7 and 41.7 μg/kg (n = 31, mean = 17.2 μg/kg, SD = 7.5). For some animals blood pH values were measured following the apnoea and reached low levels (min pH 6.8). For animals that were immobilised several times there were no indications of changed sensitivity to etorphine as reflected in unchanged induction times. Mortalities could neither be related to the doses of agonist and antagonist, nor to the times of administration of the drugs. From this (n = 69) and other (n = 103) studies involving etorphine immobilisation of walruses (both Atlantic and Pacific) the overall success rate is 83 % (8 % casualty rate). We conclude that the combination etorphine‑ diprenorphine is suitable for both single and multiple immobilisations of walruses provided that (a) a casualty rate of 7-8% is acceptable (b) the antagonist diprenorphine is administered fast and well into a tissue with good blood irrigation, and (c) the animal is promptly intubated endotracheally to facilitate the restoration of breathing after drug-induced apnoea.
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Genetic signals of historic and recent migration between sub-populations of Atlantic walrus Odobenus rosmarus rosmarus west and east of Greenland
Endangered Species Research, 2009Co-Authors: Liselotte Wesley Andersen, Øystein Wiig, Ian Gjertz, E.w. Born, D. W. Doidge, R.s. WaplesAbstract:Defining sub-populations and determining migration rates between them is crucial for sound management and conservation. This also applies to the Atlantic walrus Odobenus rosmarus rosmarus, which is still exploited although population levels are low in some cases and information on abundance is lacking in others. Analysis of muscle and skin tissues using 11 nuclear microsatellite markers from a total of 297 Atlantic walruses from the Hudson Strait across W, NW and E Greenland to Svalbard and Franz Josef Land was undertaken to determine the number of sub-populations, their ancestral origin and the contemporary rates and directions of migration (gene flow) between the var- ious areas. The study indicated the existence of 5 sub-populations in the Hudson Strait, W Greenland, NW Greenland, E Greenland and Franz Josef Land-Svalbard. Identification of the Hudson Strait sub- population was novel; although differences between animals here and in W Greenland were small, they were statistically significant and indicated that walruses in the Hudson Strait could be a popu- lation source for walruses for the W Greenland sub-population. The direction of migration (Hudson Strait to W Greenland) suggested a genetic signal from a historical large-scale counter-clockwise perennial migration pattern in the Baffin Bay region. The study provides essential information on population sub-structuring that is a prerequisite for management of Atlantic walruses at sustainable levels.
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A review of the genetic relationships of Atlantic walrus ( Odobenus rosmarus rosmarus ) east and west of Greenland
Polar Biology, 2001Co-Authors: Erik W. Born, Ian Gjertz, Liselotte Wesley Andersen, Øystein WiigAbstract:Studies of the genetic variation involving allozymes, mitochondrial and nuclear DNA (microsatellites) in walruses (Odobenus rosmarus) were reviewed. In addition, the genetic relationships of a total of 211 Atlantic walruses, O. r. rosmarus, from 5 sampling areas west and east of Greenland were studied using 12 nuclear DNA-microsatellite loci and restriction fragment length polymorphism obtained from the ND1, ND2 and ND3/4 segments of the mitochondrial DNA (mtDNA). At the mtDNA level, no divergence was observed among the three sampling areas east of Greenland (i.e. East Greenland, Svalbard and Franz Josef Land), whereas areas west of Greenland (i.e. Northwest and West Greenland) showed some differentiation. The genetic variation at the microsatellite loci grouped the individuals into four sub-populations: Northwest Greenland, West Greenland, East Greenland and a common Svalbard-Franz Josef Land sub-population. A significant correlation between genetic distance and geographic distance between the sampling areas (isolation-by-distance effect) was detected, especially at the mtDNA level. At a small-scale phylo-geographical level, the mtDNA data indicated that Atlantic walruses have diverged into two major groups: one northwest (i.e. in the North Water) and one east of Greenland (i.e. an East Greenland-Svalbard-Franz Josef Land group), whereas the haplotype distribution in the West Greenland sample reflected a mixture of both these groups. The microsatellite data supported a general grouping of walruses to the west and east of Greenland.
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Use of skin biopsies for assessing levels of organochlorines in walruses (Odobenus rosmarus)
Polar Biology, 2000Co-Authors: Øystein Wiig, Ian Gjertz, Vidar Berg, Dana J. Seagars, Janneche Utne SkaareAbstract:Skin and blubber samples of ten adult male Pacific walruses (Odobenus rosmarus divergens) from Alaska were used to investigate the relationship between organochlorine (OC) levels in skin and blubber of individuals. For analyses we selected 11 components that were quantified in the blubber of all individuals: hexachlorocyclohexanes (αHCH and βHCH), the DDT (dichlorodiphenyltrichloroethane) metabolite p,p′DDE, oxychlordane, and 7 individual PCB congeners, 28, 99, 105, 118, 138, 153 and 180. The correlation between the levels in the two types of tissues was significant and the relation was isometric for all components. The regression coefficient between levels in blubber (dependent variable) and levels in skin (independent variable) was different from 1 for only four of the components. The mean levels in the two types of tissues were significantly different for 3 of the 11 chemical components (βHCH, oxychlordane, and PCB28). Although this analysis is based on only ten individuals, we propose that skin samples taken by biopsy darts can be used to monitor OC levels in walruses. In August 1993 skin biopsies were collected from 25 adult male Atlantic walruses (O. r. rosmarus) at haul-out sites in southeastern Svalbard in the Norwegian Arctic and from 28 walruses of different sex and age at haul-out sites at Franz Josef Land in the Russian Arctic. The mean levels of OCs were 2–10 times higher at Svalbard than at Franz Josef Land. The dominant OC component was PCB153 in both areas. A principal component analysis detected differences between areas in OC levels but not in patterns. Since the Franz Josef Land samples were mainly taken from females and young individuals and the Svalbard samples were taken largely from adult males, we believe the differences in tissue OC levels observed from these areas can be explained by differences in sex and age of the walrus sampled. Comparable organochlorine levels in skin samples from walruses from other areas are not available. However, compared to the corresponding OC levels found in walrus blubber in other areas, the OC levels from Svalbard and Franz Josef Land are higher. The high levels of OCs in walruses from Svalbard and Franz Josef Land may be a combined effect of high pollution level in the environment and seal-eating habits. In the present study we show that it is possible to use skin biopsies taken by a non-destructive method to assess OC levels in walruses.
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Levels of cadmium and mercury in the hair of Atlantic walruses (Odobenus rosmarus rosmarus) from Svalbard, Norway
Polar Biology, 1999Co-Authors: Øystein Wiig, Aristeo Renzoni, Ian GjertzAbstract:Hair samples of 15 adult male Atlantic walruses (Odobenus rosmarus rosmarus) collected from anaesthetized individuals at Svalbard, Norway, were analysed for cadmium and total mercury. The mean level of cadmium was 0.860 ± 0.321 μg/g dry weight (median = 0.811, range = 0.349–1.51 μg/g dry weight) and the mean level of mercury was 0.235 ± 0.100 μg/g dry weight (median = 0.251, range = 0.121–0.424 μg/g dry weight). Levels of cadmium and mercury in hair of walruses from other areas are not known. Both cadmium and mercury levels in hair of walruses from Svalbard are relatively low compared to the levels found in the hair of other marine mammal species. It has been documented from a number of marine species, including marine mammals such as ringed seals and polar bears, that both cadmium and mercury levels at Svalbard are lower than in other areas. It is uncertain as to what degree levels in hair reflect levels in internal organs in walruses. In rare and highly endangered species or populations tissue samples can be difficult to collect. In walruses, it is possible to collect hair from anaesthetized individuals or at the haul-out sites during moult, to monitor heavy metal levels of the population.
Chadwick V. Jay - One of the best experts on this subject based on the ideXlab platform.
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Demography of the Pacific walrus (Odobenus rosmarus divergens) in a changing Arctic
Marine Mammal Science, 2017Co-Authors: Rebecca L. Taylor, Chadwick V. Jay, Mark S. Udevitz, John J. Citta, Lori T. Quakenbush, Patrick R. Lemons, Jonathan A. SnyderAbstract:The Pacific walrus (Odobenus rosmarus divergens) is a candidate to be listed as an endangered species under United States law, in part, because of climate change-related concerns. While the population was known to be declining in the 1980s and 1990s, its recent status has not been determined. We developed Bayesian models of walrus population dynamics to assess the population by synthesizing information on population sizes, age structures, reproductive rates, and harvests for 1974–2015. Candidate models allowed for temporal variation in some or all vital rates, as well as density dependence or density independence in reproduction and calf survival. All selected models indicated that the population underwent a multidecade decline, which began moderating in the 1990s, and that annual reproductive rate and natural calf survival rates rose over time in a density-dependent manner. However, selected models were equivocal regarding whether the natural juvenile survival rate was constant or decreasing over time. Depending on whether juvenile survival decreased after 1998, the population growth rate either increased during 1999–2015 or stabilized at a lesser level of decline than seen in the 1980s. The probability that the population was still declining in 2015 ranged from 45% to 87%.
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Evaluation of a method using survey counts and tag data to estimate the number of Pacific walruses (Odobenus rosmarus divergens) using a coastal haulout in northwestern Alaska
Polar Biology, 2017Co-Authors: Brian C. Battaile, Chadwick V. Jay, Mark S. Udevitz, Anthony S. FischbachAbstract:Increased periods of sparse sea ice over the continental shelf of the Chukchi Sea in late summer have reduced offshore haulout habitat for Pacific walruses ( Odobenus rosmarus divergens ) and increased opportunities for human activities in the region. Knowing how many walruses could be affected by human activities would be useful to conservation decisions. Currently, there are no adequate estimates of walrus abundance in the northeastern Chukchi Sea during summer–early autumn. Estimating abundance in autumn might be possible from coastal surveys of hauled out walruses during periods when offshore sea ice is unavailable to walruses. We evaluated methods to estimate the size of the walrus population that was using a haulout on the coast of northwestern Alaska in autumn by using aerial photography to count the number of hauled out walruses (herd size) and data from 37 tagged walruses to estimate availability (proportion of population hauled out). We used two methods to estimate availability, direct proportions of hauled out tagged walruses and smoothed proportions using local polynomial regression. Point estimates of herd size (4200–38,000 walruses) and total population size (76,000–287,000 walruses) ranged widely among days and between the two methods of estimating availability. Estimates of population size were influenced most by variation in estimates of availability. Coastal surveys might be improved most by counting walruses when the greatest numbers are hauled out, thereby reducing the influence of availability on population size estimates. The chance of collecting data during peak haulout periods would be improved by conducting multiple surveys.
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Sex-Specific Energetics of Pacific Walruses (Odobenus rosmarus divergens) during the Nursing Interval
Physiological and biochemical zoology : PBZ, 2016Co-Authors: Shawn R. Noren, Mark S. Udevitz, Chadwick V. JayAbstract:Habitat use and activity patterns of Pacific walruses (Odobenus rosmarus divergens) have changed with climate-induced reductions in sea ice. Increases in the time active in water could result in negative energy balance, precluding females from sustaining lactation, which could impact population demographics. Little is known about lactation costs in walruses. We examined the energetics of 0-2-yr-old walrus calves by using Bayesian hierarchical models based on longitudinal husbandry records of growth (n = 6 females and 7 males) and caloric intake (n = 5 females and 6 males) as a proxy for maternal lactation costs. Males and females had similar growth patterns; mean mass increased from 68 kg at birth to 301 kg by 2 yr. Females had a 2,000 kcal kg(-1) higher mass storage (growth) cost than males; females typically synthesize and deposit greater amounts of adipose, which is more energy dense than lean tissue. In contrast, males had higher metabolic (basal and activity) costs, ranging from 600 to 1,800 kcal d(-1) greater than similarly sized females; males are typically leaner, and muscle is more metabolically active than adipose. Yet total daily energy requirements (storage plus metabolic components) were similar across sexes, summing to approximately 190,000 kcal over the first month postpartum. Based on these estimates and assuming that 8,103 kcal is recovered from 1 kg of mass loss in adult female walruses, suckling calves could deplete 23 kg of their mother's body mass over the first month after parturition if none of the lactation costs is met through ingested prey.
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Energy Demands for Maintenance, Growth, Pregnancy, and Lactation of Female Pacific Walruses (Odobenus rosmarus divergens)
Physiological and biochemical zoology : PBZ, 2014Co-Authors: Shawn R. Noren, Mark S. Udevitz, Chadwick V. JayAbstract:Decreases in sea ice have altered habitat use and activity patterns of female Pacific walruses Odobenus rosmarus divergens and could affect their energetic demands, reproductive success, and population status. However, a lack of physiological data from walruses has hampered efforts to develop the bioenergetics models required for fully understanding potential population-level impacts. We analyzed long-term longitudinal data sets of caloric consumption and body mass from nine female Pacific walruses housed at six aquaria using a hierarchical Bayesian approach to quantify relative energetic demands for maintenance, growth, pregnancy, and lactation. By examining body mass fluctuations in response to food consumption, the model explicitly uncoupled caloric demand from caloric intake. This is important for pinnipeds because they sequester and deplete large quantities of lipids throughout their lifetimes. Model outputs were scaled to account for activity levels typical of free-ranging Pacific walruses, averaging 83% of the time active in water and 17% of the time hauled-out resting. Estimated caloric requirements ranged from 26,900 kcal d(-1) for 2-yr-olds to 93,370 kcal d(-1) for simultaneously lactating and pregnant walruses. Daily consumption requirements were higher for pregnancy than lactation, reflecting energetic demands of increasing body size and lipid deposition during pregnancy. Although walruses forage during lactation, fat sequestered during pregnancy sustained 27% of caloric requirements during the first month of lactation, suggesting that walruses use a mixed strategy of capital and income breeding. Ultimately, this model will aid in our understanding of the energetic and population consequences of sea ice loss.
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Spatial variation and low diversity in the major histocompatibility complex in walrus (Odobenus rosmarus)
Polar Biology, 2014Co-Authors: Sarah A. Sonsthagen, Chadwick V. Jay, Krystal Fales, George K. Sage, Sandra L. TalbotAbstract:Increased global temperature and associated changes to Arctic habitats will likely result in the northward advance of species, including an influx of pathogens novel to the Arctic. How species respond to these immunological challenges will depend in part on the adaptive potential of their immune response system. We compared levels of genetic diversity at a gene associated with adaptive immune response [Class II major histocompatibility complex (MHC), DQB exon 2] between populations of walrus ( Odobenus rosmarus ), a sea ice-dependent Arctic species. Walrus was represented by only five MHC DQB alleles, with frequency differences observed between Pacific and Atlantic populations. MHC DQB alleles appear to be under balancing selection, and most (80 %; n = 4/5) of the alleles were observed in walruses from both oceans, suggesting broad scale differences in the frequency of exposure and diversity of pathogens may be influencing levels of heterozygosity at DQB in walruses. Limited genetic diversity at MHC, however, suggests that walrus may have a reduced capacity to respond to novel immunological challenges associated with shifts in ecological communities and environmental stressors predicted for changing climates. This is particularly pertinent for walrus, since reductions in summer sea ice may facilitate both northward expansion of marine species and associated pathogens from more temperate regions, and exchange of marine mammals and associated pathogens through the recently opened Northwest Passage between the Atlantic and Pacific Oceans in the Canadian high Arctic.
