Sumatran tiger Soyono—who, at 19 years old was considered an elderly tiger—was humanely euthanized by veterinarians at the Smithsonian National Zoological Park on Monday morning, according to a zoo statement.
Soyono—affectionately known as Soy—began exhibiting common signs of aging in early October, according to the statement.
"Keepers noticed that she walked more slowly and seemed to have trouble with her balance. Zoo veterinarians monitored Soy’s health and administered medication to alleviate the symptoms associated with spondylosis—a degenerative disorder of the spine that can create abnormal pressure on the nerves," the statement reported.
"Animal care staff made the decision to euthanize Soy when they observed that her health and quality of life continued to steadily decline despite treatments," the statement added.
The average lifespan for a wild Sumatran tiger is 15 years. With human care, the tigers may live into their late teens or early 20s.
Soyono was born at the National Zoo on June 14, 1993, and gave birth to seven cubs—born in 2001, 2004 and 2006—fathered by her mate, Rokan. Soyono's mother had been caught in the wild, so Soyono's "genes were not well-represented in the North American population, making her a valuable breeder," according to the zoo's statement. Her cubs traveled to North American and international zoos for breeding and research.
Sumatran tigers are listed as critically endangered by the International Union for Conservation of Nature. There are only about 700 left in the world, with about 400 living in the forests of their native Indonesia. The National Zoo’s Conservation Biology Institute is a member of the Global Tiger Initiative, which is working to double the number of wild tigers by 2022.
Two Sumatran tigers still live at the zoo: a young female tiger, Damai, and a male tiger, Kavi, the zoo reported.