Relationship Between the Social Structure and Potential Reproductive Success in Muroid Rodents (Rodentia, Myomorpha)

Abstract

In many systematic groups of mammalian species, the evolution of sociality leads to the formation of large social groups (group-size evolution). In rodents, however, the most social species live in family groups consisting, as a rule, of not numerous individuals. The family-group lifestyle of some ground-dwelling sciurids (Sciuridae) and voles (Microtus) results in fewer breeding adult females, a decreased litter size, and a longer time till first reproduction. Statistical analysis of published data has been conducted in the present study and has shown that transition to the family-group lifestyle leads to a decreased potential reproductive success in many muroid rodents: females produce fewer litters and, consequently, fewer pups during the reproduction season. However, the potential reproductive success in muroid rodents with a family-group lifestyle could be increased due to delayed offspring dispersal (who spend the severe winter period in family groups) and extensive cooperation in foraging, defending their territory and food stores, as well as in care-giving activities. One can suggest that females of these species produce fewer offspring, but of “better quality”. Ultimately, social rodent species may gain inclusive fitness benefits because of the higher fitness of their offspring as compared to solitary dwellers and gregarious species.