If murder is defined in human terms—the killing of members of the same species— then some species do indeed commit murder. This could be the result of an altercation to determine dominance within the group or a battle over a resource like food or a mate. Animals, including lions and langur monkeys, have also been known to commit infanticide—the killing of infants of their own species; in most of these cases, infanticide has been linked to the arrival of a new alpha male in the group. Scientists surmise that by killing the infants in the group (who were fathered by some other male), the new alpha can bring their mothers into sexual receptivity faster and thus ensure a chance for reproductive success.