Isotopic investigation of niche partitioning among native carnivores and the non-native coyote (Canis latrans)

^†Contribution to Special Section ‘Stable Isotopes in Mammals’.

Abstract

We employed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes within a hypothetico-deductive framework to explore potential resource partitioning among terrestrial mammalian carnivores. Isotope values were acquired using guard hair samples from bobcat (Lynx rufus), coyote (Canis latrans), gray fox (Urocyon cinereoargenteus), and red fox (Vulpes vulpes) in the Adirondack Park, NY, USA. Enrichment along the δ¹³C axis was expected to reflect the use of human sources of food (reflecting a corn subsidy), and by extension tolerance for human-modified environments, whereas enrichment along the δ¹⁵N axis was expected to reflect a higher level of carnivory (i.e. amount of animal-based protein in the diet) – two mechanisms by which these now sympatric species may achieve a dynamic coexistence. Although bobcats were the only obligate carnivore, all four species shared a similar δ¹⁵N space. In contrast, bobcat had a lower and distinct δ¹³C signature compared to foxes, consistent with the a priori expectation of bobcats being the species least tolerant of human activities. Isotope signatures for coyotes, which colonized the region in the 1920s, overlapped all three native carnivores, bobcats the least, gray fox the most, indicating their potential competitive influence on this suite of native carnivores.

Keywords:

• animals
• bobcat
• carbon-13
• coexistence
• coyote
• food
• gray fox
• hair
• isotope ecology
• niche partitioning
• red fox

Acknowledgements

We thank the New York state hunters and trappers who allowed us to sample their furbearer pelts and N. Mitchell for collection of fruit and small mammals. We also thank the Stable Isotope Lab at the State University of New York College of Environmental Science and Forestry (SUNY-ESF) for running our samples.

Funding

This work was conducted with funding from the Northeastern States Research Cooperative [grant #10DG11242307048] through funding made available by the USDA Forest Service. The conclusions and opinions in this paper are those of the authors and not of the NSRC, the Forest Service, or the USDA. Additional support was provided by the SUNY-ESF Samuel Grober Graduate Fellowship.

Notes

^† Contribution to Special Section ‘Stable Isotopes in Mammals’.