Using Stable Isotopes to Infer Diet Specialization in Cougars (Puma concolor)
Cougars (Puma concolor) are a generalist species composed of individuals that specialize to varying degrees on certain prey types. Specialization on a specific prey type can be the result of prey availability and/or behavioural differences in prey selection between individual cougars. In systems where individual cougars select prey disproportionately to availability, small prey populations risk extirpation resulting from asymmetric apparent competition with more abundant prey. In other words, cougars are able to subsidize themselves on abundant primary prey while depleting the population of secondary selected prey. The Government of Alberta employs a generalist hunting strategy, based on quotas allocated to WMUs (Wildlife Management Units), to manage cougar populations. This method may not remove specialist individuals that could have harmful repercussions on small prey populations. Current methods for determining the prey composition of individual cougars are costly and laborious, relying primarily on kill site investigation of GPS collared cougars and/or scat analysis. Using stable isotope analysis, we hope to develop a non-invasive, cost effective method for identifying specialist individuals. This method is based on the assumption that you “are what you eat”; the contribution of assimilated C and N to consumer tissues is proportional to the biomass of prey consumed. With the completion of our study, we hope to provide the Government of Alberta with a tool that can be used to help redefine management practices in order to target specialist cougars that threaten small prey populations.
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