The birth of a Galápagos tortoise is already an exciting event, since there are only 15,000 of the reptiles left. But an even more thrilling event happened last May: A tiny white tortoise with red eyes hatched at a zoo in Switzerland. It’s the first albino Galápagos tortoise born in captivity.

Albinism is a recessive trait. To be colorless, an organism has to inherit two recessive genes, or units of hereditary material—one from each parent. An offspring with one gene for albinism and one typical gene will have typical coloring, like the albino tortoise’s sibling that hatched four days later! The two tortoises are now on display at the zoo for everyone to see.