The study of "helpers at the nest" has received much attention in the avian literature but comparatively little in mammals. The proposed study will be the first extensive investigation in the order Rodentia and will provide insights into the evolution of apparently altruistic behaviors that can be examined in other species. Also, this study will examine the long-term effects of the presence or absense of older siblings on the behavior and reproductive success of younger sibs. The dynamics of family groups are important in population processes in Microtus ochrogaster. Knowledge of the behavior of prairie voles can be important in regulating population densities below a level which would result in serious economic problems.//
