Social biology of rodents.

Herein, I summarize some basic components of rodent social biology. The material in this paper is summarized and condensed from a recent book "Rodent Societies: An Ecological and Evolutionary Perspective" edited by J. O. Wolff and P. W. Sherman (2007). I describe the four basic spacing patterns and illustrate how female territoriality is a function of offspring defense and male mating tactics are a function of female defensibility. The vulnerability of young to infanticide shapes female spacing and mating behavior. Food does not appear to be a defensible resource for rodents, except for those species that larder hoard nonperishable items such as seeds. Philopatry and the formation of kin groups result in genetic sub-structuring of the population, which in turn affects effective population size and genetic diversity. Dispersal is male biased and typically involves emigration from the maternal site to avoid female relatives and to seek unrelated mates. Scent marking is a major form of communication and is used in reproductive competition and to assess prospective mates, but it is also eavesdropped by predators to locate prey. Females do not appear to alter the sex ratio of litters in response to maternal condition but among arvicoline rodents daughters appear to be favored in spring and sons in autumn. Rodents are relatively monomorphic; however, females tend to be larger than males in the smallest species and smaller in the larger species. Predation risk results from an interaction among foraging time and vulnerability and in turn affects behavioral and life history characteristics.