The Smithsonian National Zoo's 20-year-old Andean bear was euthanized this week after his health had begun declining rapidly.
The bear, named Nikki, had been with the zoo for five years and sired two cubs, named Bernardo and Chaska, during that time.
The zoo reports that Nikki suffered from an ulcer on his lower jaw in 2011 that wouldn't heal. It was later revealed to be cancerous. Nikki went through chemotherapy and did well for about a year before the ulcers spread to other parts of his body.
"It's always hard to lose an animal we care so much about, and we feel very lucky to have had Nikki as part of the National Zoo family," said Craig Saffoe, curator of Great Cats and Bears at the National Zoo, in a statement. "He was a really cool bear gushing with personality, which made him a favorite amongst visitors and keepers alike."
Andean bears generally live between 20 to 25 years when cared for by humans. They are South America's only bear species and it's estimated that there are about 2,000 left in the wild.