Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics

Abstract

Summary1. Understanding how seasonal environmental conditions affect the timing and distribution of synchronized animal movement patterns is a central issue in animal ecology. 2. Migration, a behavioural adaptation to seasonal environmental fluctuations, is a fundamental part of the life history of numerous species. However, global climate change can alter the spatiotemporal distribution of resources and thus affect the seasonal movement patterns of migratory animals. 3. We examined sea ice dynamics relative to migration patterns and seasonal geographical fidelity of an Arctic marine predator, the polar bear (Ursus maritimus). Polar bear movement patterns were quantified using satellite-linked telemetry data collected from collars deployed between 1991-1997 and 2004-2009. 4. We showed that specific sea ice characteristics can predict the timing of seasonal polar bear migration on and off terrestrial refugia. In addition, fidelity to specific onshore regions during the ice-free period was predicted by the spatial pattern of sea ice break-up but not by the timing of break-up. The timing of migration showed a trend towards earlier arrival of polar bears on shore and later departure from land, which has been driven by climate-induced declines in the availability of sea ice. 5. Changes to the timing of migration have resulted in polar bears spending progressively longer periods of time on land without access to sea ice and their marine mammal prey. The links between increased atmospheric temperatures, sea ice dynamics, and the migratory behaviour of an ice-dependent species emphasizes the importance of quantifying and monitoring relationships between migratory wildlife and environmental cues that may be altered by climate change.

Assessing polar bear (Ursus maritimus) population structure in the Hudson Bay region using SNPs

“…Similar to many other species, natal philopatry may also be a driving factor in the development of genetic structure (e.g., snow goose, Avise, Alisauskas, Nelson, & Ankney, 1992; prairie voles, McGuire, Getz, Hofmann, Pizzuto, & Frase, 1993; walleye, Stepien & Faber, 1998; Antarctic seals, Davis, Stirling, Strobeck, & Coltman, 2008). Although knowledge on the subject is not extensive, polar bears do exhibit seasonal site fidelity throughout their range (Born, Wiig, & Thomassen, 1997; Cherry, Derocher, Thiemann, & Lunn, 2013; Derocher & Stirling, 1990; Harrington, 1968; Lone, Aars, & Ims, 2013; Ramsay & Stirling, 1990). This could be the case for individuals with membership in the Southeast cluster, which were exclusively sampled in James Bay (Akimiski Island).…”

Polar Bear Foraging Behavior During the Ice-Free Period in Western Hudson Bay: Observations, Origins, and Potential Significance

“…It is likely becoming more prevalent in WH because the bears are onshore longer. They also are increasingly overlapping new and increasingly abundant prey species and they may be coming ashore with an energy deficit (Cherry et al, 2013;Gormezano andRockwell, 2013a, 2013b). Such foraging appears to be increasing at other northern locations as well (Stirling and Derocher, 2012).…”

“…However, it is not known what proportion of individuals in the WH population is currently exploiting the land-based resources, although it is likely that not all bears are doing so (Gormezano andRockwell, 2013a, 2013b). Onshore arrival of WH polar bears is temporally staggered (Cherry et al, 2013) and no doubt some individuals arrive after certain resources become unavailable (e.g., incubating snow geese, calving caribou). Furthermore, individuals may differ in physical constraints (e.g., size; Brose, 2010), skills, or learning experiences (Lunn and Stirling, 1985), and this could translate into individual variation in choice or capture success of various prey (e.g., Caldow et al, 1999;Estes et al, 2003).…”

Identifying shifts in maternity den phenology and habitat characteristics of polar bears (Ursus maritimus) in Baffin Bay and Kane Basin

“…First date on land (FDOL) was defined as the date that the bear first came onto land without returning to the sea ice until freeze-up the following fall (Cherry et al 2013). For the pregnant bears, the first date on land was the date after which the bear did not return to the sea ice until she emerged in the spring.…”