WHY ARE FEMALE SMALL MAMMALS TERRITORIAL

I question the widely accepted view that female small mammals are territorial to defend food, and suggest that theoretical and empirical evidence are more compatible with a pup-defense hypothesis to protect young from infanticide. The fact that females are territorial during the time of greatest food abundance and not during food limitation (such as winter) contradicts a food-defense hypothesis. Energy conservation through huddling does not appear sufficient to explain shared use of space during nonbreeding seasons. Aggression and territorial defense are most intense during lactation and are directed toward other females, those most likely to commit infanticide, and not toward males and other food competitors. Plasticity in territoriality and shared use of space are more closely associated with lactation, density dependent factors, and overlap of kin groups than to species-specific food habits. Thus, distribution, abundance, and type of food resource do not in themselves explain female territoriality. As female spacing patterns play an important role in behavioral and population ecology, an understanding of the proximate causation and ultimate benefits of territoriality is essential to comprehending small mammal population dynamics. I recommend that future studies on female spacing patterns take into consideration population density and kin groups, and use an experimental design that tests the predictions of alternative hypotheses.