Space use of a dominant Arctic vertebrate: Effects of prey, sea ice, and land on Pacific walrus resource selection

Beatty, William S.; Jay, Chadwick V.; Fischbach, Anthony S.; Grebmeier, Jacqueline M.; Taylor, Rebecca L.; Blanchard, Arny L.; Jewett, Stephen C.

doi:10.1016/j.biocon.2016.08.035

Cited by 28 publications

(24 citation statements)

References 52 publications

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“…However in sandy nearshore sediments of the north‐east Bering Sea, walruses excavated large individuals of the bivalve Mya truncata Linnaeus buried to a mean depth of 32 cm, the bivalve Macoma buried to a mean of 17 cm, and Serripes buried to a mean of 11 cm (Oliver et al, ). van Veen grabs such as ours do not sample these deeply buried bivalves, so evaluations of feeding habitat for walruses are incomplete (Beatty et al, ; Jay et al, ). Nevertheless, the presence of smaller (younger) bivalves near the sediment surface may indicate larger individuals buried deeper, and in the past, side‐scan sonar detected extensive areas of walrus feeding furrows in what appear to have been type‐3 habitats in the Chirikov Basin (Nelson & Johnson, ).…”

Section: Discussionmentioning

confidence: 99%

Sediment organic carbon integrates changing environmental conditions to predict benthic assemblages in shallow Arctic seas

Lovvorn

North

Grebmeier

et al. 2018

Aquatic Conservation

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In marine spatial planning, conserving adequate habitats and the food webs they support requires delineating habitats and projecting future trends. For bottom‐feeding marine birds and mammals, repeated benthic sampling over large areas to document changes and to develop predictive models of prey dispersion is quite costly. More easily monitored variables that relate strongly to the biomass and structure of benthic assemblages, and are more readily predicted from physical models of climate change, would facilitate planning efforts. The organic carbon (OC) content of sediments integrates diverse physical and biotic processes, and can be less variable over time than primary production, salinity, temperature, or position of water masses. Sediment OC further subsumes inputs at the base of food webs that can limit carbon flows to higher taxa. For the northern Bering Sea, this study explored the utility of sediment OC as a predictor of benthic assemblage types. Cluster analysis and multi‐dimensional scaling distinguished three main types along a gradient of sediment OC. The assemblage for highest sediment OC had a much greater biomass of brittlestars, diverse marine worms, and two mid‐sized, thinner‐shelled bivalves selected as prey by diving sea ducks. The assemblage for lowest sediment OC lacked brittlestars, had a much greater biomass of amphipods sought by gray whales (Eschrichtius robustus), and had a much higher biomass of two often larger or thicker‐shelled bivalves commonly targeted by walruses (Odobenus rosmarus). Areas of exceptionally low sediment OC tended towards dominance by sand dollars with low foraging value. Our study shows that sediment OC has promise as a proxy for monitoring and predicting changes in important prey assemblages in a given region. Models that link predicted hydrographic patterns to lateral advection of phytodetritus, and the resulting sediment OC, may further allow the use of physical climate models to project the future dispersion of benthic habitats for endothermic predators.

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Section: Discussionmentioning

confidence: 99%

Sediment organic carbon integrates changing environmental conditions to predict benthic assemblages in shallow Arctic seas

Lovvorn

North

Grebmeier

et al. 2018

Aquatic Conservation

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“…In this study, important feeding habitat was delineated by a simulation model of prey densities needed by eiders to achieve energy balance (Lovvorn et al 2015). An alternative approach to mapping important habitats is use of resource selection functions that statistically relate telemetry locations of animals to environmental variables such as prey density, ice conditions or water depth (Dickson & Smith 2013; Beatty et al 2016). Although based on actual animal locations, the resource selection approach of comparing used versus unused areas can be compromised if ice cover, adverse weather or lack of omniscience about prey locations prevents the animals from occupying the better benthic habitats during periods when telemetry data are collected.…”

Section: Discussionmentioning

confidence: 99%

Sustaining ecological and subsistence functions in conservation areas: eider habitat and access by Native hunters along landfast ice

Lovvorn¹,

Rocha²,

Mahoney

et al. 2018

Envir. Conserv.

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SUMMARYIn the Arctic, rapid climate change has kindled efforts to delineate and project the future of important habitats for marine birds and mammals. These animals are vital to subsistence economies and cultures, so including the needs of both animals and hunters in conservation planning is key to sustaining social-ecological systems. In the northeast Chukchi Sea, a nearshore corridor of open water is a major spring migration route for half a million eider ducks that are hunted along the landfast ice. Zoning areas for industrial activities or conservation should consider both eider habitat and hunter access to those habitats from the variable ice edge. Based on benthic sampling in 2010‒2012, a model of eider foraging energetics and satellite data on ice patterns in April and May 1997‒2011, we mapped the range of positions of the landfast ice edge relative to a given dispersion of habitat suitable for eider feeding. In some sectors, feeding areas were too limited or too far from landfast ice to provide regular hunting access. In other sectors, overlap of the ice edge with eider feeding habitat was quite variable, but often within a consistent geographic range. Areas accessible to hunters were a small fraction of total eider habitat, so areas adequate for conserving eiders would not necessarily include areas that meet the hunters’ needs. These results can inform spatial planning of industrial activities that yield cash income critical to subsistence hunting in less developed locations. Our study provides an approach for mapping ‘subsistence conservation areas’ throughout the Arctic and an example for such efforts elsewhere.

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“…For example, polar bears have been observed attacking walruses hauled out on the coast in the fall, and Alaskan hunters have reported the consumption of spotted seals in winter (Voorhees, Sparks, Huntington, & Rode, ). The changing phenology of Arctic sea ice (Serreze, Crawford, Stroeve, Barrett, & Woodgate, ) is altering polar bear's behavior and habitat selection (Rode et al., ; Ware et al., ) and, combined with the ecosystem response to ice loss (e.g., Feng, Ji, Campbell, Ashjian, & Zhang, ; Moore, ), may be shifting the composition of prey species available to polar bears (e.g., Beatty et al., ; Galicia, Thiemann, Dyck, Ferguson, & Higdon, ).…”

Section: Discussionmentioning

confidence: 99%

“…The changing phenology of Arctic sea ice (Serreze, Crawford, Stroeve, Barrett, & Woodgate, 2016) is altering polar bear's behavior and habitat selection Ware et al, 2017) and, combined with the ecosystem response to ice loss (e.g., Feng, Ji, Campbell, Ashjian, & Zhang, 2016;Moore, 2016), may be shifting the composition of prey species available to polar bears (e.g., Beatty et al, 2016;Galicia, Thiemann, Dyck, Ferguson, & Higdon, 2016).…”

Section: Discussionmentioning

confidence: 99%

Simultaneous estimation of diet composition and calibration coefficients with fatty acid signature data

Bromaghin

Budge

Thiemann

et al. 2017

Ecology and Evolution

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Knowledge of animal diets provides essential insights into their life history and ecology, although diet estimation is challenging and remains an active area of research. Quantitative fatty acid signature analysis (QFASA) has become a popular method of estimating diet composition, especially for marine species. A primary assumption of QFASA is that constants called calibration coefficients, which account for the differential metabolism of individual fatty acids, are known. In practice, however, calibration coefficients are not known, but rather have been estimated in feeding trials with captive animals of a limited number of model species. The impossibility of verifying the accuracy of feeding trial derived calibration coefficients to estimate the diets of wild animals is a foundational problem with QFASA that has generated considerable criticism. We present a new model that allows simultaneous estimation of diet composition and calibration coefficients based only on fatty acid signature samples from wild predators and potential prey. Our model performed almost flawlessly in four tests with constructed examples, estimating both diet proportions and calibration coefficients with essentially no error. We also applied the model to data from Chukchi Sea polar bears, obtaining diet estimates that were more diverse than estimates conditioned on feeding trial calibration coefficients. Our model avoids bias in diet estimates caused by conditioning on inaccurate calibration coefficients, invalidates the primary criticism of QFASA, eliminates the need to conduct feeding trials solely for diet estimation, and consequently expands the utility of fatty acid data to investigate aspects of ecology linked to animal diets.

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Space use of a dominant Arctic vertebrate: Effects of prey, sea ice, and land on Pacific walrus resource selection

Cited by 28 publications

References 52 publications

Sediment organic carbon integrates changing environmental conditions to predict benthic assemblages in shallow Arctic seas

Sediment organic carbon integrates changing environmental conditions to predict benthic assemblages in shallow Arctic seas

Sustaining ecological and subsistence functions in conservation areas: eider habitat and access by Native hunters along landfast ice

Simultaneous estimation of diet composition and calibration coefficients with fatty acid signature data

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