Social and nutritional stressors: agents for altered immune function in white-footed mice (Peromyscus leucopus)

Abstract

As habitats become more fragmented, population densities and diets of wildlife can change dramatically, contributing to increased stress and incidence of infections and disease. To better understand effects of human disturbance on immunocompetence of wild mammals, we studied individual and combined effects of social and nutritional stress on the health of wild-captured adult male white-footed mice (Peromyscus leucopus (Rafinesque, 1818)), a species that commonly occurs in close proximity to humans. Paired mice had reduced body mass and circulating monocytes, higher serum corticosterone level, and a significantly weaker humoral immune response compared with mice housed individually. Mice fed a 5% protein diet had reduced body mass and circulating monocytes, but no differences in humoral or cellular immune responses compared with mice fed a 30% protein diet. The only interactive effect of the two stresses on immune-related parameters was on mass of the spleen. We hypothesize that reduced humoral immunocompetence in response to acute and chronic social stress likely contributes to increases in disease transmission in high-density populations associated with fragments of habitat. In addition, anthropogenic impacts that limit food availability may be of greater importance to immune function than impacts on food quality.