Document Type
Poster Session
Department
Biological Sciences
Faculty Mentor
Christine Maher, PhD
Abstract
When two species compete for food, one species typically outcompetes the other. Subordinate species can alleviate costs of competition by reducing diet overlap, promoting coexistence. Non-native coyotes (Canis latrans) and historically native gray foxes (Urocyon cineroargenteus) have expanded their range in Maine and may compete with native red foxes (Vulpes vulpes). Yet, we lack information about potential competition for these species. To investigate competition, we analyzed stable isotopes and stomach contents to determine if coyotes, red foxes, and gray foxes differed in use of anthropogenic foods and trophic position. Based on previous work, we predicted that coyotes utilize anthropogenic foods the least (lowest δ13C), and red foxes utilize anthropogenic foods the most (highest δ13C), and that coyotes occupy the highest trophic position (highest δ15N), with gray foxes at the lowest trophic position (lowest δ15N). Furthermore, we predicted that gray fox diets consist primarily of plant matter and overlap to a greater degree with red foxes than with coyotes, and conversely that coyote diets consist primarily of animal prey and overlap most with red foxes. We will present data on stable isotopes, comparing δ13C and δ15N to assess relative resource use among species, and diet, comparing frequency of occurrence (%) of prey items taken from stomach contents. These results can help us to understand the potential for competition and coexistence among three canid species as their ranges expand in Maine.
Open Access?
1
Competition and Coexistence Among Canids in Maine
When two species compete for food, one species typically outcompetes the other. Subordinate species can alleviate costs of competition by reducing diet overlap, promoting coexistence. Non-native coyotes (Canis latrans) and historically native gray foxes (Urocyon cineroargenteus) have expanded their range in Maine and may compete with native red foxes (Vulpes vulpes). Yet, we lack information about potential competition for these species. To investigate competition, we analyzed stable isotopes and stomach contents to determine if coyotes, red foxes, and gray foxes differed in use of anthropogenic foods and trophic position. Based on previous work, we predicted that coyotes utilize anthropogenic foods the least (lowest δ13C), and red foxes utilize anthropogenic foods the most (highest δ13C), and that coyotes occupy the highest trophic position (highest δ15N), with gray foxes at the lowest trophic position (lowest δ15N). Furthermore, we predicted that gray fox diets consist primarily of plant matter and overlap to a greater degree with red foxes than with coyotes, and conversely that coyote diets consist primarily of animal prey and overlap most with red foxes. We will present data on stable isotopes, comparing δ13C and δ15N to assess relative resource use among species, and diet, comparing frequency of occurrence (%) of prey items taken from stomach contents. These results can help us to understand the potential for competition and coexistence among three canid species as their ranges expand in Maine.
