While researching lions in Zambia, biologist Thandiwe Mweetwa noticed that lionesses within a pride will all have cubs around the same time.

When she looked into it further, Mweetwa learned lionesses sync their fertility cycles so that they can all raise their young together.

There's a reason for that. “Synchronized estrus is thought to increase reproductive success in the pride,” says Mweetwa, a National Geographic emerging explorer and Big Cats Initiative grantee. Having cubs at the same time means that mother lions can rely on each other to nurse, babysit, and protect the youngsters. (See "12 Amazing Pictures of Lions.")

This safety in numbers also allows more lions to survive to adulthood. Predation is a great threat