科研之友
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摘要
Predation is an ecological interaction influenced by abiotic and biotic factors acting on multiple temporal scales, yet multi-temporal comparisons are rare in empirical studies. For polar bears Ursus maritimus, the physical configuration of the habitat and conditions in which seals are hunted may change on intra-and inter-seasonal scales. Additionally, while the effects of climate change on polar bears have focused on linking reductions in sea ice to body condition and survival, the potential changes to on-ice hunting conditions have not been examined. Employing observational counts of seals killed by polar bears between early-April and late-May 1985-2011 (n = 650), we modelled the likelihood of predation events in the Beaufort Sea, Canada at multi-temporal scales. We used the top model to estimate the expected kill rate of seals in the springs of 1985-1986 and 2005-2006 and integrated the result with fasting rates derived from physiological markers in blood samples. A log-likelihood ratio test suggested a multi-temporal approach fit the seal kill data better than any single scale alone. Predation events were influenced by ringed seal Pusa hispida reproduction and haul-out behaviour, regional sea ice concentration and the phase of climatic indices. The expected kill rate from the top predation model and the estimated mean biomass of seal kills were significant predictors of polar bear fasting rates. Results suggest that 50% less seal biomass was killed in 2005-2006 than in 1985-1986, which correlates with a significant increase in the frequency of polar bears in a fasting state. We propose that the documented changes in polar bear fasting rates between 1985-1986 and 2005-2006 are due to a complex set of abiotic and biotic factors including underlying prey dynamics, rather than a single-scale environmental correlation.
- 出版日期2015-8
