scholarly journals Subsurface swimming and stationary diving are metabolically cheap in adult Pacific walruses (Odobenus rosmarus divergens)

2021 ◽  
Author(s):  
Alicia Borque-Espinosa ◽  
Karyn D. Rode ◽  
Diana Ferrero-Fernández ◽  
Anabel Forte ◽  
Romana Capaccioni-Azzati ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Surface ◽  
Marine Mammals ◽  
Benthic Habitat ◽  
Metabolic Rates ◽  
Energetic Costs ◽  
Odobenus Rosmarus Divergens ◽  
Odobenus Rosmarus ◽  
Free Ranging ◽  
The Impact

Walruses rely on sea-ice to efficiently forage and rest between diving bouts while maintaining proximity to prime foraging habitat. Recent declines in summer sea ice have resulted in walruses hauling out on land where they have to travel farther to access productive benthic habitat while potentially increasing energetic costs. Despite the need to better understand the impact of sea ice loss on energy expenditure, knowledge about metabolic demands of specific behaviours in walruses is scarce. In the present study, 3 adult female Pacific walruses (Odobenus rosmarus divergens) participated in flow-through respirometry trials to measure metabolic rates while floating inactive at the water surface during a minimum of 5 min, during a 180-second stationary dive, and while swimming horizontally underwater for ∼90 m. Metabolic rates during stationary dives (3.82±0.56 l O2 min−1) were lower than those measured at the water surface (4.64±1.04 l O2 min−1), which did not differ from rates measured during subsurface swimming (4.91±0.77 l O2 min−1). Thus, neither stationary diving nor subsurface swimming resulted in metabolic rates above those exhibited by walruses at the water surface. These results suggest that walruses minimize their energetic investment during underwater behaviours as reported for other marine mammals. Although environmental factors experienced by free-ranging walruses (e.g., winds or currents) likely affect metabolic rates, our results provide important information for understanding how behavioural changes affect energetic costs and can be used to improve bioenergetics models aimed at predicting the metabolic consequences of climate change on walruses.

scholarly journals Activity-specific metabolic rates for diving, transiting, and resting at sea can be estimated from time-activity budgets in free-ranging marine mammals

2017 ◽  
Vol 7 (9) ◽  
pp. 2969-2976 ◽  
Author(s):  
Tiphaine Jeanniard-du-Dot ◽  
Andrew W. Trites ◽  
John P. Y. Arnould ◽  
John R. Speakman ◽  
Christophe Guinet
Keyword(s):  
Marine Mammals ◽  
Metabolic Rates ◽  
Activity Budgets ◽  
Time Activity ◽  
Free Ranging

Thyroid hormone concentrations in captive and free-ranging West Indian manatees (Trichechus manatus)

2000 ◽  
Vol 203 (23) ◽  
pp. 3631-3637 ◽  
Author(s):  
R.M. Ortiz ◽  
D.S. MacKenzie ◽  
G.A. Worthy
Keyword(s):  
Thyroid Hormone ◽  
Food Consumption ◽  
Marine Mammals ◽  
Critical Role ◽  
West Indian ◽  
Water Salinity ◽  
Metabolic Rates ◽  
Trichechus Manatus ◽  
Total Thyroxine ◽  
Free Ranging

Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic rates reported for manatees suggest that thyroid hormone concentrations in these animals may also be reduced. However, thyroid hormone concentrations have yet to be examined in manatees. The effects of captivity, diet and water salinity on plasma total triiodothyronine (tT(3)), total thyroxine (tT(4)) and free thyroxine (fT(4)) concentrations were assessed in adult West Indian manatees (Trichechus manatus). Free-ranging manatees exhibited significantly greater tT(4) and fT(4) concentrations than captive adults, regardless of diet, indicating that some aspect of a captive existence results in reduced T(4) concentrations. To determine whether this reduction might be related to feeding, captive adults fed on a mixed vegetable diet were switched to a strictly sea grass diet, resulting in decreased food consumption and a decrease in body mass. However, tT(4) and fT(4) concentrations were significantly elevated over initial values for 19 days. This may indicate that during periods of reduced food consumption manatees activate thyroid-hormone-promoted lipolysis to meet water and energetic requirements. Alterations in water salinity for captive animals did not induce significant changes in thyroid hormone concentrations. In spite of lower metabolic rates, thyroid hormone concentrations in captive manatees were comparable with those for other terrestrial and marine mammals, suggesting that the low metabolic rate in manatees is not attributable to reduced circulating thyroid hormone concentrations.

Pacific walrus diet across 4000 years of changing sea ice conditions

2019 ◽  
pp. 1-17 ◽  
Author(s):  
Casey T. Clark ◽  
Lara Horstmann ◽  
Anne de Vernal ◽  
Anne M. Jensen ◽  
Nicole Misarti
Keyword(s):  
Sea Ice ◽  
Chukchi Sea ◽  
Trophic Position ◽  
Bone Collagen ◽  
Pacific Walrus ◽  
Odobenus Rosmarus Divergens ◽  
Odobenus Rosmarus ◽  
Trophic Changes ◽  
Primary Driver ◽  
Ice Conditions

AbstractDeclining sea ice is expected to change the Arctic's physical and biological systems in ways that are difficult to predict. This study used stable isotope compositions (δ13C and δ15N) of archaeological, historic, and modern Pacific walrus (Odobenus rosmarus divergens) bone collagen to investigate the impacts of changing sea ice conditions on walrus diet during the last ~4000 yr. An index of past sea ice conditions was generated using dinocyst-based reconstructions from three locations in the northeastern Chukchi Sea. Archaeological walrus samples were assigned to intervals of high and low sea ice, and δ13C and δ15N were compared across ice states. Mean δ13C and δ15N values were similar for archaeological walruses from intervals of high and low sea ice; however, variability among walruses was greater during low-ice intervals, possibly indicating decreased availability of preferred prey. Overall, sea ice conditions were not a primary driver of changes in walrus diet. The diet of modern walruses was not consistent with archaeological low sea ice intervals. Rather, the low average trophic position of modern walruses (primarily driven by males), with little variability among individuals, suggests that trophic changes to this Arctic ecosystem are still underway or are unprecedented in the last ~4000 yr.

Developmental changes in circulatory vitamin A (retinol) and its transport proteins in free-ranging harbour seal (Phoca vitulina) pups

2000 ◽  
Vol 78 (10) ◽  
pp. 1862-1868 ◽  
Author(s):  
Wendy Simms ◽  
Peter S Ross
Keyword(s):  
Vitamin A ◽  
Marine Mammals ◽  
Environmental Contaminants ◽  
Phoca Vitulina ◽  
Transport Proteins ◽  
Developmental Changes ◽  
Harbour Seal ◽  
Retinol Binding Protein ◽  
Free Ranging ◽  
The Impact

Although vitamin A (retinol) levels are highly regulated within individual organisms, natural (e.g., age, sex, disease) and anthropogenic (e.g., environmental contaminants) factors can affect the dynamics of this essential nutrient. In this study, we examined developmental changes in the circulatory vitamin A system of free-ranging harbour seal (Phoca vitulina) pups by collecting serial blood samples from healthy known-age animals throughout their nursing period. While harbour seal pups were born with relatively low levels of circulatory retinol (144.4 ± 13.9 µg/L), nursing animals more than doubled these levels within 2 days (385.0 ± 46.9 µg/L), and levels continued to rise more gradually until weaning (431.0 ± 35.8 µg/L). Animals that were not nursing, such as orphaned (184.4 ± 34.2 µg/L), fasted (347.0 ± 14.4 µg/L), and weaned (204.5 ± 38.5 µg/L) pups, had significantly lower circulatory retinol levels. Despite the developmental changes observed in total retinol, the concentration of retinol bound by its transport proteins, retinol binding protein and transthyretin, remained relatively constant throughout the nursing period. This suggests that, like most mammals, the delivery of retinol to target tissues is highly regulated in harbour seal pups. Furthermore, the high concentrations of circulatory retinol observed in harbour seal pups may serve to saturate transport proteins, ensuring a steady delivery of vitamin A to target tissues during a period of potentially variable supply. Understanding how natural factors affect circulatory retinol and its transport proteins is an important facet of assessing the impact of environmental contaminants on vitamin A dynamics in marine mammals.

scholarly journals Female Pacific walruses (Odobenus rosmarus divergens) show greater partitioning of sea ice organic carbon than males: Evidence from ice algae trophic markers

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0255686
Author(s):  
Chelsea W. Koch ◽  
Lee W. Cooper ◽  
Ryan J. Woodland ◽  
Jacqueline M. Grebmeier ◽  
Karen E. Frey ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Sea Ice ◽  
Nitrogen Isotopes ◽  
Chukchi Sea ◽  
Trophic Position ◽  
Ice Algae ◽  
Pacific Walrus ◽  
Odobenus Rosmarus Divergens ◽  
Odobenus Rosmarus ◽  
The Pacific

The expected reduction of ice algae with declining sea ice may prove to be detrimental to the Pacific Arctic ecosystem. Benthic organisms that rely on sea ice organic carbon (iPOC) sustain benthic predators such as the Pacific walrus (Odobenus rosmarus divergens). The ability to track the trophic transfer of iPOC is critical to understanding its value in the food web, but prior methods have lacked the required source specificity. We analyzed the H-Print index, based on biomarkers of ice algae versus phytoplankton contributions to organic carbon in marine predators, in Pacific walrus livers collected in 2012, 2014 and 2016 from the Northern Bering Sea (NBS) and Chukchi Sea. We paired these measurements with stable nitrogen isotopes (δ15N) to estimate trophic position. We observed differences in the contribution of iPOC in Pacific walrus diet between regions, sexes, and age classes. Specifically, the contribution of iPOC to the diet of Pacific walruses was higher in the Chukchi Sea (52%) compared to the NBS (30%). This regional difference is consistent with longer annual sea ice persistence in the Chukchi Sea. Within the NBS, the contribution of iPOC to walrus spring diet was higher in females (~45%) compared to males (~30%) for each year (p < 0.001), likely due to specific foraging behavior of females to support energetic demands associated with pregnancy and lactation. Within the Chukchi Sea, the iPOC contribution was similar between males and females, yet higher in juveniles than in adults. Despite differences in the origin of organic carbon fueling the system (sea ice versus pelagic derived carbon), the trophic position of adult female Pacific walruses was similar between the NBS and Chukchi Sea (3.2 and 3.5, respectively), supporting similar diets (i.e. clams). Given the higher quality of organic carbon from ice algae, the retreat of seasonal sea ice in recent decades may create an additional vulnerability for female and juvenile Pacific walruses and should be considered in management of the species.

scholarly journals Observations of Annual Walrus (Odobenus rosmarus divergens) Migrations in the Nearshore Waters of the Chukotka Peninsula from 1990 to 2012

ARCTIC ◽  
2020 ◽  
Vol 73 (1) ◽  
pp. 99-113
Author(s):  
Vladimir V. Melnikov
Keyword(s):  
Marine Mammals ◽  
Chukchi Sea ◽  
Relative Number ◽  
Bering Strait ◽  
Pacific Walrus ◽  
Odobenus Rosmarus Divergens ◽  
Odobenus Rosmarus ◽  
Commercial Harvest ◽  
The Pacific ◽  
Pass Through

After the end of the commercial harvest, research regarding the Pacific walrus (Odobenus rosmarus divergens) in Russia was reduced and focused on the observation of animals at land-based haul-outs. This paper presents the long-term observations of the distribution, relative abundance, and direction of seasonal movements of walruses in the offshore waters of the Chukotka Peninsula, based on data obtained in 1990 – 2012. Observations of Pacific walruses and other marine mammals were conducted mainly from April through November, but some were conducted all year round. In some years up to 30 Native Chukotkan observers were employed at this task. Some watched from observation posts in Native villages onshore, and others from motorboats during hunting trips. These observations have shown that walruses are rare in January and February in the nearshore waters of the Chukotka Peninsula. Their numbers begin to increase in March. The northward movement of walruses begins in April, and walruses migrate from the Bering Sea to the Chukchi Sea throughout the summer months and early autumn. Based on observations from posts located directly in front of the southern Bering Strait, I conclude that 106 – 1055 walruses pass through the Bering Strait from July to September, to the northwest and north. At the haul-outs in the Gulf of Anadyr, the relative number of walruses remains stable during the summer (up to 11 000 individuals at all haul-outs in total based on observers’ estimates) and decreases only with the appearance of ice in October – November.

scholarly journals Panmixia in a sea ice-associated marine mammal: evaluating genetic structure of the Pacific walrus (Odobenus rosmarus divergens) at multiple spatial scales

2020 ◽  
Vol 101 (3) ◽  
pp. 755-765 ◽  
Author(s):  
William S Beatty ◽  
Patrick R Lemons ◽  
Suresh A Sethi ◽  
Jason P Everett ◽  
Cara J Lewis ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Sea Ice ◽  
Spatial Scales ◽  
Pacific Walrus ◽  
Ice Dynamics ◽  
Odobenus Rosmarus Divergens ◽  
Odobenus Rosmarus ◽  
The Pacific ◽  
Kin Structure ◽  
Broad Scale

Abstract The kin structure of a species at relatively fine spatial scales impacts broad-scale patterns in genetic structure at the population level. However, kin structure rarely has been elucidated for migratory marine mammals. The Pacific walrus (Odobenus rosmarus divergens) exhibits migratory behavior linked to seasonal patterns in sea ice dynamics. Consequently, information on the spatial genetic structure of the subspecies, including kin structure, could aid wildlife managers in designing future studies to evaluate the impacts of sea ice loss on the subspecies. We sampled 8,303 individual walruses over a 5-year period and used 114 single-nucleotide polymorphisms to examine both broad-scale patterns in genetic structure and fine-scale patterns in relatedness. We did not detect any evidence of genetic structure at broad spatial scales, with low FST values (≤ 0.001) across all pairs of putative aggregations. To evaluate kin structure at fine spatial scales, we defined a walrus group as a cluster of resting individuals that were less than one walrus body length apart. We found weak evidence of kin structure at fine spatial scales, with 3.72% of groups exhibiting mean relatedness values greater than expected by chance, and a significantly higher overall observed mean value of relatedness within groups than expected by chance. Thus, the high spatiotemporal variation in the distribution of resources in the Pacific Arctic environment likely has favored a gregarious social system in Pacific walruses, with unrelated animals forming temporary associations.

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