HPA activity and neotic and anxiety-like behavior vary among Peromyscus species.

Behaviorally plastic species are more likely to invade and endure in new areas, and behaviorally plastic individuals tend to be attracted to novelty (i.e., neophilic). Furthermore, neophilic behaviors are often influenced by glucocorticoids. Thus in addition to environmental conditions and vicariant events, behavioral plasticity and its endocrinological mediators may influence the extent of vertebrate geographic distributions. Some species of mice in the genus, Peromyscus, occupy most of North America whereas others are restricted to small areas. We predicted that one widespread species (Peromyscus maniculatus) would interact more with novel objects, more readily explore novel environments, and possess hypo-responsive HPA axes compared to species with small ranges. Our hypothesis was not supported, but given the small number of species in this study and the high anxiety-like behavior in captive P. maniculatus, it is premature to reject the hypothesis that behavioral flexibility affects geographic distribution in Peromyscus. Indeed, behavioral and HPA axis variation was complementary among species, which is opposite of the pattern typically detected within species, suggesting that future studies of glucocorticoid mediation of neotic and anxiety-like behaviors in Peromyscus would be valuable.