Sacramento Zoo officials say a 20-year-old zebra has been euthanized after a rapid decline in health. The Grevy's zebra named Mara was put down Sunday.
Zookeepers and veterinarians had been monitoring Mara for three weeks as she became progressively lethargic, lost weight and eventually stopped eating and drinking.
The zoo says Mara was quiet, dependable, and had learned to knock on the door to let zookeepers know she was ready for breakfast.
Mara was one of five of the endangered zebra species at the zoo and the other four are in good health.
Grevy's zebras live in a nutrient-poor region of Africa and have a different social organization than other zebras.