Why do females not resist infanticide?
Females may defend offspring against some males, particularly against all-male groups attacking their group, but females rarely resist infanticide by a new alpha male. A strong hypothesis that explains this is a study by Yamamura and Ito (1990) in which they tested the hypothesis that females who do not resist infanticide “may recover the loss of offspring by gaining more grandchildren if their sons inherit the infanticidal trait more than sons of resistant females.” The study proved this hypothesis wrong, however, showing instead that the costs and benefits of resistance are responsible for the obedience in some female lemurs. It has also been shown that females influence infanticide by signaling to the new alpha male whether she will allow him to commit infanticide (Hrdy, 1979). Females benefit from infanticide in that, by allowing a new male to kill her unweaned infants, a female may go into estrus soon after infanticide and mate with the new male. A female is motivated to mate with
