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Fox-Dobbs, K.L., 2006

The foraging ecology of late Quaternary mammalian and avian carnivores: A stable isotope approach

Bibliographic Reference

Fox-Dobbs, K.L., 2006, The foraging ecology of late Quaternary mammalian and avian carnivores: A stable isotope approach: University of California, Santa Cruz, Ph.D. dissertation, 186 p.


Stable isotopic studies of ancient and modern vertebrates reveal food web connectivity, and provide insight into how species interactions change through time in response to environmental shifts. I investigate the foraging behaviors of past and present populations of carnivores and their prey, and the ecosystems in which they lived. Carnivore-specific stable isotope variables, such as trophic enrichment values, are required to correctly interpret predator-prey interactions. I report collagen trophic fractionations for a terrestrial hypercarnivore (gray wolf) with a fully characterized diet, and compare levels of intra-populational isotopic variability among North American wolf populations. This study is focused on the wolves of Isle Royale that are part of a geographically isolated and simple food web, with prey limited to moose and beaver. Predator-prey co-evolutionary relationships can be preserved through millennia, but human impacts such as exploitation or habitat destruction, can disturb these interactions on the timescale of years. Wolf prey selection and habitat use is conserved between historic (pre-extinction) and modern (post-reintroduction) gray wolf populations in Yellowstone National Park, despite their 70-year absence from the ecosystem. Carnivore dietary preferences are correlated to patterns of species extinction versus survival. The extinction of many Pleistocene species of avian scavengers coincided with the mammalian megafaunal extinction that occurred at the Pleistocene-Holocene boundary. My results suggest that dependence on terrestrial megafaunal carrion as a food source led to the extinction of the inland California condor populations and coastal populations of teratorns and black vultures, whereas use of marine foods allowed coastal condor populations to survive. Paleontological records can be used to investigate how carnivore ecology shifted in response to past episodes of environmental change. Two such recent periods of rapid climate change are the Last Glacial Maximum and the end of glacial conditions at the beginning of the Holocene. Pleistocene gray wolves from eastern Beringia (Alaska) maintained a varied diet throughout the late Pleistocene, and were not specialized predators of a particular prey species. Post-glacial wolves have lower variances in [delta] 13 C and [delta] 15 N values than older wolves, suggesting increased dietary specialization prior to the megafaunal extinction event at the Pleistocene-Holocene boundary.

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