Walrus haul-out and in water activity levels relative to sea ice availability in the Chukchi Sea

Jay, Chadwick V.; Taylor, Rebecca L.; Fischbach, Anthony S.; Udevitz, Mark S.; Beatty, William S.

doi:10.1093/jmammal/gyw195

Cited by 28 publications

(47 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The negative correlation between time in the water and sea ice availability quantified by our activity model is consistent with results of Jay et al. () who found that the probability of being hauled out in the eastern Chukchi Sea was greatest when sea ice was available. This may be a consequence of walruses having to travel further from coastal haulout sites to foraging areas when sea ice is not available (Jay et al.…”

Section: Discussionsupporting

confidence: 92%

“…This may be a consequence of walruses having to travel further from coastal haulout sites to foraging areas when sea ice is not available (Jay et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…These models differ from those used by Jay et al. () because we had to use data from a much larger area and we had to use broad‐scale predictor variables that could be projected by general circulation models. We also used the radio‐tag data to identify seasonal movement patterns and develop models of the timing of walrus movements among regions as functions of ice conditions.…”

Section: Methodsmentioning

confidence: 99%

“…Following Jay et al. (), we used the two‐pool isotope dilution estimates of field metabolic rate (

\overset{x}{true}

= 5.5 × Kleiber) from Acquarone et al. () and the mean resting metabolic rate from above ( C r = 1.8) to adjust for the time spent resting, giving a mean value of C a = 6.8 × Kleiber.…”

Section: Methodsmentioning

confidence: 99%

“…More recently, Jay et al. () used data from radio‐tagged walruses to quantify the linkages between walrus activity patterns and the availability of sea ice. Also, Noren et al.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Forecasting consequences of changing sea ice availability for Pacific walruses

et al. 2017

Self Cite

View full text Add to dashboard Cite

Abstract. The accelerating rate of anthropogenic alteration and disturbance of environments has increased the need for forecasting effects of environmental change on fish and wildlife populations. Models linking projections of environmental change with behavioral responses and bioenergetic effects can provide a basis for these forecasts. There is particular interest in forecasting effects of projected reductions in sea ice availability on Pacific walruses (Odobenus rosmarus divergens). Declining extent of summer sea ice in the Chukchi Sea has caused Pacific walruses to increase use of coastal haulouts and decrease use of more productive offshore feeding areas. Such climate-induced changes in distribution and behavior could ultimately affect the status of the population. We developed behavioral models to relate changes in sea ice availability to adult female walrus movements and activity levels, and adapted previously developed bioenergetics models to relate those activity levels to energy requirements and the ability to meet those requirements. We then linked these models to general circulation model projections of future ice availability to forecast autumn body condition for female walruses during mid-and late-century time periods. Our results suggest that as sea ice becomes less available in the Chukchi Sea, female walruses will spend more time in the southwestern region of that sea, less time resting, and less time foraging. Median forecasted autumn body masses were 7-12% lower in future scenarios than during recent times, but posterior distributions broadly overlapped and median forecasted seasonal mass losses (15-34%) were comparable to seasonal mass losses routinely experienced by other pinnipeds. These seasonal reductions in body condition would be unlikely to result in demographic effects, but if walruses were unable to rebuild endogenous reserves while wintering in the Bering Sea, cumulative effects could have implications for reproduction and survival, ultimately affecting the status of the Pacific walrus population. Our approach provides a general framework for forecasting consequences of the broad range of environmental changes and anthropogenic disturbances that may affect bioenergetics through behavioral responses or changes in prey availability.

show abstract

Section: Discussionsupporting

confidence: 92%

“…This may be a consequence of walruses having to travel further from coastal haulout sites to foraging areas when sea ice is not available (Jay et al. ).…”

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…Following Jay et al. (), we used the two‐pool isotope dilution estimates of field metabolic rate (

\overset{x}{true}

= 5.5 × Kleiber) from Acquarone et al. () and the mean resting metabolic rate from above ( C r = 1.8) to adjust for the time spent resting, giving a mean value of C a = 6.8 × Kleiber.…”

Section: Methodsmentioning

confidence: 99%

“…More recently, Jay et al. () used data from radio‐tagged walruses to quantify the linkages between walrus activity patterns and the availability of sea ice. Also, Noren et al.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Forecasting consequences of changing sea ice availability for Pacific walruses

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

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

et al. 2023

Self Cite

View full text Add to dashboard Cite

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

show abstract

Assessing the sustainability of Pacific walrus harvest in a changing environment

Johnson,

Eisaguirre,

Taylor

et al. 2024

J Wildl Manag

View full text Add to dashboard Cite

Harvest sustainability is a primary goal of wildlife management and conservation, and in a changing world, it is increasingly important to consider environmental drivers of population dynamics alongside harvest in cohesive management plans. This is particularly pertinent for harvested species that acutely experience effects of climate change. The Pacific walrus (Odobenus rosmarus divergens), a crucial subsistence resource for Indigenous communities, is simultaneously subject to rapid habitat loss associated with diminishing sea ice and an increasing anthropogenic footprint in the Arctic. We developed a theta‐logistic population modeling‐management framework to evaluate various harvest scenarios combined with 4 potential climate and disturbance scenarios (ranging from optimistic to pessimistic, based largely on sea ice projections from general circulation models) to simulate Pacific walrus population dynamics to the end of the twenty‐first century, focusing on the independent‐aged female subset of the population. We considered 2 types of harvest strategies: 1) state‐dependent harvest scenarios wherein we calculated harvest as a percentage of the population and updated annual harvests at set intervals as the population was reassessed, and 2) annually consistent harvest scenarios wherein annual harvest levels remain consistent into the future. All climate and disturbance scenarios indicated declines of varying severity in Pacific walrus abundance to the end of the twenty‐first century, even in the absence of harvest. However, we found that a state‐dependent annual harvest of 1.23% of the independent‐aged female subset of the population (e.g., 1,280 independent‐aged females harvested in 2020, similar to contemporary harvest levels) met our criterion for sustainability under all climate and disturbance scenarios, considering a medium risk tolerance level of 25%. This indicates that the present rate of Pacific walrus harvest is sustainable and will continue to be—provided the population is assessed at regular intervals and harvest is adapted to match changes in population dynamics. Our simulations indicate that a sustainable annually‐consistent harvest is also possible but only at low levels if the population declines as expected. Applying a constant annual harvest of 1,280 independent‐aged females failed to meet our criterion for sustainability under 3 of the 4 climate and disturbance scenarios we evaluated and had a higher probability of quasi‐extinction than an equivalent state‐dependent harvest scenario (1.23%). We highlight the importance of state‐dependent management strategies and suggest our modeling framework is useful for managing harvest sustainability in a changing climate.

show abstract

Walrus haul-out and in water activity levels relative to sea ice availability in the Chukchi Sea

Cited by 28 publications

References 26 publications

Forecasting consequences of changing sea ice availability for Pacific walruses

Forecasting consequences of changing sea ice availability for Pacific walruses

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

Assessing the sustainability of Pacific walrus harvest in a changing environment

Contact Info

Product

Resources

About