Narrator: This is Science Today. Almost forty percent of gorilla infant deaths are caused by a male gorilla who isn't the father. A new study by Sandy Harcourt, an anthropologist at the University of California, Davis, looked into how female gorillas can and do prevent infanticide. He found that gorillas, unlike chimpanzees, can't mate with numerous males in an effort to make them all think they're the father.
Harcourt: The thing about gorillas, they have such a short travel distance per day and such a short period of heat that it turns out that actually, they cannot mate with enough males to prevent all the other males being infanticidal.
Narrator: Instead, female gorillas have to mate with one powerful male so he'll protect their infant. The males don't have to make the same kind of choice.
Harcourt: There's a powerful male in the area and the females individually join him. He gets the benefit of having a bunch of females-each female is mating with only that one male. So the females are monogamous if you like, he's polygamous.
Narrator: For Science Today, I'm Larissa Branin.