Two of the four 10-week-old cheetah cubs are introduced to the outdoors under the watchful eye of their mother Tumai at the National Zoo in February 2005. (Gerald Herbert/AP)

Tumai, the cheetah who gave birth in 2004 to the first litter of cheetah cubs born at the National Zoo, has died of a tumor, the zoo announced Friday.

At 13, Tumai had outlived the median life span of captive cheetahs by three years and was the oldest of the six cheetahs on exhibit at the zoo.

Spokeswoman Pamela Baker-Masson said that zookeepers did not know she was sick until she died, most likely of a tumor that caused her spleen to rupture.

The four cubs that she gave birth to in 2004 were sent to zoos in New Jersey, Oregon and Wisconsin so that they could breed with other cheetahs.

Tumai’s litter was heralded as a momentous step in breeding the endangered animals, fewer than 10,000 of which still live in the wild.

“We’re all trying so hard to breed cheetahs,” Baker-Masson said. “It’s always very sad when we lose anybody, but she was just remarkable because of what she contributed to the overall cheetah population.”

Two more cubs were born at the National Zoo last summer.