Polar bear–grizzly bear interactions during the autumn open-water period in Alaska

Miller, Susanne; Wilder, James M.; Wilson, Ryan R.

doi:10.1093/jmammal/gyv140

Cited by 77 publications

(32 citation statements)

References 52 publications

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“…Our estimates of the total energetic value of a carcass are conservative because polar bears sometimes consume internal organs and cartilage (Miller et al . ). Putrefaction or consumption by other scavengers (eg foxes, ravens) may also reduce or alter the nutritional value of stranded whales to some extent, although polar bears have been observed feeding on carcasses for well over a year.…”

Section: Whales and Polar Bearsmentioning

confidence: 97%

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Historical and potential future importance of large whales as food for polar bears

Laidre

Stirling

Estes

et al. 2018

Frontiers in Ecol & Environ

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Polar bears (Ursus maritimus) are expected to be adversely impacted by a warming Arctic due to melting of the sea‐ice platform from which they hunt ice‐breeding seals. We evaluated the hypothesis that scavenging on stranded large whale carcasses may have facilitated polar bear survival through past interglacial periods during which sea‐ice was limited by analyzing: (1) present‐day scavenging by polar bears on large whale carcasses; (2) energy values of large whale species; and (3) the ability of polar bears, like the brown bears (Ursus arctos) from which they evolved, to quickly store large amounts of lipids and to fast for extended periods. We concluded that scavenging on large whale carcasses likely facilitated survival of polar bears in past interglacial periods when access to seals was reduced. In a future, ice‐impoverished Arctic, whale carcasses are less likely to provide nutritional refuge for polar bears because overharvesting by humans has greatly reduced large whale populations, carcass availability is geographically limited, and climate‐induced sea‐ice loss is projected to occur at a more rapid pace than polar bears have experienced at any previous time in their evolutionary history.

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Section: Whales and Polar Bearsmentioning

confidence: 97%

“…; Miller et al . ), but they are unlikely to survive on a diet based primarily on terrestrial resources (Rode et al . ).…”

Section: Foraging Behaviormentioning

confidence: 99%

Historical and potential future importance of large whales as food for polar bears

Laidre

Stirling

Estes

et al. 2018

Frontiers in Ecol & Environ

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show abstract

“…Unlike grizzly and black bears, which are able to survive on vegetative diets, polar bears must hunt seals to survive (Rode et al 2010b). As a result, polar bears may be more averse to physical confrontations than grizzly bears, contrary to the common assertion that they are the most aggressive of bears (Miller et al 2015). This is likely because, throughout their evolution, the presence of other large terrestrial Pleistocene predators (such as short-faced bears [Arctodus spp.]…”

Section: Difference In Attacks By North American Bear Speciesmentioning

confidence: 99%

Polar bear attacks on humans: Implications of a changing climate

et al. 2017

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Understanding causes of polar bear (Ursus maritimus) attacks on humans is critical to ensuring both human safety and polar bear conservation. Although considerable attention has been focused on understanding black (U. americanus) and grizzly (U. arctos) bear conflicts with humans, there have been few attempts to systematically collect, analyze, and interpret available information on human‐polar bear conflicts across their range. To help fill this knowledge gap, a database was developed (Polar Bear‐Human Information Management System [PBHIMS]) to facilitate the range‐wide collection and analysis of human‐polar bear conflict data. We populated the PBHIMS with data collected throughout the polar bear range, analyzed polar bear attacks on people, and found that reported attacks have been extremely rare. From 1870–2014, we documented 73 attacks by wild polar bears, distributed among the 5 polar bear Range States (Canada, Greenland, Norway, Russia, and United States), which resulted in 20 human fatalities and 63 human injuries. We found that nutritionally stressed adult male polar bears were the most likely to pose threats to human safety. Attacks by adult females were rare, and most were attributed to defense of cubs. We judged that bears acted as a predator in most attacks, and that nearly all attacks involved ≤2 people. Increased concern for both human and bear safety is warranted in light of predictions of increased numbers of nutritionally stressed bears spending longer amounts of time on land near people because of the loss of their sea ice habitat. Improved conflict investigation is needed to collect accurate and relevant data and communicate accurate bear safety messages and mitigation strategies to the public. With better information, people can take proactive measures in polar bear habitat to ensure their safety and prevent conflicts with polar bears. This work represents an important first step towards improving our understanding of factors influencing human‐polar bear conflicts. Continued collection and analysis of range‐wide data on interactions and conflicts will help increase human safety and ensure the conservation of polar bears for future generations. © 2017 The Wildlife Society.

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“…A common assumption is that grizzly bears will dominate in direct competitions with black bears because adult grizzlies typically are larger and more aggressive than black bears. While there are empirical examples of this (Gunther et al 2002), recent studies exploring interference competition have found exceptions to this assumption, with the outcome having more to do with motivation and perception of risk than body size (Miller et al 2015, Allen et al 2016). Actual encounter rates, their outcome, and effects on emergent properties (Salt 1979) like density have not been thoroughly evaluated for either species (Mattson et al 2005, Schwartz et al 2010.…”

Section: Introductionmentioning

confidence: 99%

Using spatially‐explicit capture–recapture models to explain variation in seasonal density patterns of sympatric ursids

2018

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Understanding how environmental factors interact to determine the abundance and distribution of animals is a primary goal of ecology, and fundamental to the conservation of wildlife populations. Studies of these relationships, however, often assume static environmental conditions, and rarely consider effects of competition with ecologically similar species. In many parts of their shared ranges, grizzly bears Ursus arctos and American black bears U. americanus have nearly complete dietary overlap and share similar life history traits. We therefore tested the hypothesis that density patterns of both bear species would reflect seasonal variation in available resources, with areas of higher primary productivity supporting higher densities of both species. We also hypothesized that interspecific competition would influence seasonal density patterns. Specifically, we predicted that grizzly bear density would be locally reduced due to the ability of black bears to more efficiently exploit patchy food resources such as seasonally abundant fruits. To test our hypotheses, we used detections of 309 grizzly and 597 black bears from two independent genetic sampling methods in spatially‐explicit capture–recapture (SECR) models. Our results suggest grizzly bear density was lower in areas of high black bear density during spring and summer, although intraspecific densities were also important, particularly during the breeding season. Black bears had lower densities in areas of high grizzly bear density in spring; however, density of black bears in early and late summer was best explained by primary productivity. Our results are consistent with the hypothesis that smaller‐bodied, more abundant black bears may influence the density patterns of behaviorally‐dominant grizzly bears through exploitative competition. We also suggest that seasonal variation in resource availability be considered in efforts to relate environmental conditions to animal density.

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Polar bear–grizzly bear interactions during the autumn open-water period in Alaska

Cited by 77 publications

References 52 publications

Historical and potential future importance of large whales as food for polar bears

Historical and potential future importance of large whales as food for polar bears

Polar bear attacks on humans: Implications of a changing climate

Using spatially‐explicit capture–recapture models to explain variation in seasonal density patterns of sympatric ursids

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