Effects of trap confinement on personality measurements in two terrestrial rodents

Abstract

In recent years individual differences in the behavior of animals, or personalities, have been shown to influence the response of individuals to changing environments and have important ecological implications. As researchers strive to understand and predict the responses of individuals and populations to anthropogenic changes, personality studies in wild populations will likely continue to increase. Studies of personality in wild populations often require that animals are live-trapped before behavioral observation can occur; however, it is unknown what impact live trapping may have on the behavior of trapped individuals. Specifically, if the duration of trap confinement directly influences behavior, then by obtaining wild animals through live-trapping are we confounding the very measurements we are most interested in? To investigate this question, we performed a study using two small mammal species. We positioned high-definition trail cameras on Longworth small mammal traps in the field to observe capture events and record the time of capture. We then measured personality in captured deer mice (Peromyscus maniculatus) and southern red-backed voles (Myodes gapperi) using three standardized tests. With a repeatability analysis, we confirmed which behaviors could be considered personality traits, and through linear and generalized linear models, we found that the time an animal had spent confined to a trap before testing did not affect the majority of behaviors exhibited. Our results showed two weak behavioral effects of confinement duration on boldness and docility depending on whether an individual had been trapped previously. Our results suggest that personality measurements of wild, trapped small mammals are not determined by trapping procedures, but that researchers should control for whether an animal is naive to trapping during analysis.