At first glance, king penguins Skip and Ping don’t appear to be too remarkable a sight when viewed by spectators at their enclosure at Germany's Zoo Berlin. But look closer and you may see one of them nurturing an egg under one of their skin folds. Skip and Ping, a same-sex penguin couple, have effectively adopted an egg and hope to raise it as their own baby.

A story by writer Liam Stack in The New York Times details their pursuit of parenthood. According to Stack, the penguins arrived at Zoo Berlin in April and were observed to have a degree of baby fever, trying to coddle everything from a rock to a fish. Taking note of their coupling, zookeepers passed on an unhatched egg laid by a female at the zoo. They immediately took to it, taking protective measures and growing ornery when employees got too close. Ping has taken to sitting on the egg in the hopes it will hatch.

That’s not guaranteed. Zookeepers aren't certain whether the egg was fertilized. If it is, it’s likely to crack open in early September, giving Skip and Ping an opportunity to expand their family.

Earlier this year, a same-sex penguin pair named Sphen and Magic began rearing a chick in Australia’s Sea Life Sydney Aquarium. The doting parents sang to and fed their adoptive offspring.

[h/t The New York Times]