The Smithsonian’s National Zoo is mourning the loss of its elderly male Sumatran tiger (Panthera tigris sumatrae), Rokan, today, while celebrating his contributions to conservation during his long life. At almost 20 years of age, Rokan lived longer than the 15-year life expectancy for Sumatran tigers in the wild and was among the oldest Sumatran tigers currently in captivity.

Rokan first showed signs of a rear-leg lameness nearly 18 months ago. Although his condition initially improved with pain medications, his lameness soon worsened. The Zoo’s veterinary team anesthetized Rokan for a complete physical examination during which time veterinarians discovered that he had a neuromuscular disorder as the result of a spinal cord disease. Rokan was treated with medications to ensure his comfort and improve his coordination. However, in December 2009, Rokan’s condition again worsened.

“We knew he would get to the point when his quality of life was no longer medically manageable or acceptable,” said Dr. Katharine Hope, associate veterinarian at the National Zoo. “Input from the veterinary team, animal keepers and curators informs the careful decisions we must make about an elderly animal’s quality of life.”

A final pathology report will indicate if Rokan had a degenerative spinal condition such as invertebral disc disease that has been reported in older, large cats.

Rokan, who was named after the Rokan River in Sumatra, was a prolific breeder. He sired 10 surviving cubs between four litters—seven males and three females—as part of the Sumatran Tiger Species Survival Plan. SSP scientists determine which captive animals should breed by considering their genetic makeup, nutritional and social needs, temperament and overall health. One of Rokan’s offspring, 4-year-old Guntur, still lives at the National Zoo. Rokan was born at the San Antonio Zoo Sept. 6, 1990, and came to the Zoo in 1997.

“Rokan was eventually retired from the SSP because he was so successful at breeding,” said Craig Saffoe, acting curator of Great Cats. “Not only did he generate interest in his species among members of the public, but he greatly contributed to the survival of Sumatran tigers.”

Although tigers are generally solitary in the wild, Rokan formed an especially strong bond with the Zoo’s elderly female tiger, Soyono, said tiger keeper Marie Magnuson, who has worked with Rokan for nearly 11 years. Soyono and Rokan had three litters of cubs together. Rokan’s physical build also made him unique, Magnuson said.

“He was unusual for a Sumatran in that he had a rather muscular, bulky build. Most Sumatrans are like swimmers—they’re sleek and sinuous. Rokan was more like a linebacker,” Magnuson said. “He was also very calm. We could run a wet vac in the next enclosure, and he’d sleep right through it. Nothing seemed to upset him, except not knowing where Soyono was.”

The Sumatran tiger is a tiger subspecies and is classified as critically endangered. Habitat loss, poaching and illegal trade have contributed to tigers’ declining populations. Save the Tiger Fund estimates that there are about 4,000 wild tigers living in Asia. Tigers live in a vast range of habitats, from the tropic rainforests of Sumatra and Indochina to the temperate oak forest of the Amur River Valley in eastern Russia.

The Smithsonian Institution has partnered with the World Bank Group, National Geographic and Global Environment Fund to develop the Global Tiger Initiative, which aims to save tigers from extinction and double the number of wild tigers by 2022. The Initiative brings together tiger-range governments and international agencies and the private sector to develop policies and practices that support these goals.