A Hyena’s Sibling Rivalry

Photo: robdray.com (flickr)

Hyena cubs like this one in Tanzania must fight for their lives from the moment they are born

If you grew up with a brother or sister, you probably know what sibling rivalry is like.  For a spotted hyena though, sibling rivalry is a matter of life and death.

Spotted hyena mothers usually have twins.  They give birth in a private burrow where the newborns live for the first few weeks of life.  By the time the mother moves her offspring from the natal burrow to the community den however, there’s a fifty-fifty chance that one of her infants will be dead.  What’s more, her children always emerge from their nursery covered with wounds.

A look inside the burrow reveals what’s going on.  After a long gestation cycle, newborn hyenas are remarkably well developed.  Like Red Riding Hood’s wolf, they have big, open eyes and full sets of teeth.  They won’t hunt for many months to come, so what are these adaptations for?

Hyena infants fight each other from the moment they’re born, and often begin their struggles inside the amniotic sac.  Same sex newborns fight to the death, while brother-sister struggles usually leave both cubs battered but alive.

You might wonder why this behavior evolved in the first place?  What possible advantage could there be in killing off your closest relative?

The answer might have to do with adult hyena table manners.  Hyenas hunt together, but once they’ve brought down their prey it’s every hyena for itself in a violent feeding frenzy, where the most vicious hyenas steal away the most food.  Fighting to the death at its mother’s teats might give an infant hyena some good practice for this adult behavior.