Plasticity of Maternal Care and Seasonal Manipulation of Masculinity in Peromyscus maniculatus

Abstract

Individual variation in maternal care has been shown to have important consequences for offspring development, physiology, and behaviour. However, investigating the evolutionary consequences of differences in maternal behaviour requires the extension of well established protocols for measuring maternal behaviour in the lab to a wild rodent species. I investigated maternal care, and associations between secondary sex ratio and individual masculinity in regards to local resource competition, in a wild rodent: the woodland deer mouse (Peromyscus maniculatus gracillis). I demonstrated that 1) wild mice display similar behaviours as laboratory mice; 2) maternal care is a plastic phenotype that decreases as population density increases over one breeding season; 3) sex ratio is not manipulated in response to local resource competition; and 4) sex ratio and masculinity are correlated in this system, and decrease with increasing population density. I conclude that maternal care and offspring masculinity change over the course of one breeding season in a wild rodent, Peromyscus maniculatus.