"We had a duck, a mallard, show up last year, and wouldn't you know she's here again. She laid her eggs, and we've got five ducklings and the mother, and they are actually co-existing with the gorillas," said Maureen Leahy, curator of primates at Lincoln Park Zoo.
It's not that the gorillas love the ducks; they probably don't. And the ducks don't even seem to notice their big hairy friends. But they do seem to have one thing in common: food.
"When there's food involved, they definitely do seem to get close to each other, but there's no competition over food or aggressive interactions over food," Leahy said.
Gorillas are basically gentile. That can be seen in a zoo video recorded when a rabbit wandered in to the gorilla habitat and Rollie, an adult female, closed in from behind.
"Very slowly creeping up behind the rabbit, so as not to spook it away, and then she gently reaches out to touch the rabbit," Leahy said.
So, the ducks and the gorillas seem to get along just fine. But what would happen if ducks or a rabbit got into an enclosure with chimpanzees, human beings' very close cousins?
"We'd probably see our chimps band together and cooperatively try to hunt for that. So, the chimps are more like us? One could say," said Leahy.
But for the ducks living with gorillas, there's not a worry in the world. Life is good. There's shelter and food.