On an isolated island in Panama, white-faced capuchin monkeys have developed unprecedented behavior. A recent study reveals how this social practice spread among young males. The ...

At first, the researchers thought it was a rare, one-time case of adoption. Monkeys have been known to “adopt” abandoned infants of the same or other species.

Scientists studying camera trap footage from Jicarón Island spotted something unusual: a capuchin monkey carrying an infant howler monkey on his back. Now, they’re trying to learn what it means.