Veterinarians at the Point Defiance Zoo and Aquarium in Tacoma killed a Sumatran tiger who was suffering from lymphoma and kidney disease.
The News Tribune reports the 14-year-old cat named Bali had been treated for more than two years.
Bali fathered two cubs at the Tacoma zoo and sired three other cubs earlier at the San Francisco zoo.
There are 71 of the critically endangered Sumatran tigers in North American zoos, including four in Tacoma. Only about 300 survive in the wild.