Garden City ? The Lee Richardszon Zoo in Garden City has euthanized a 20-year-old Amur tiger that had been in declining health for several years.

The tiger, named Boris, was euthanized Wednesday. Zoo Director Kathy Sexson says it had been suffering from arthritis and kidney disease. The median life expectancy for tigers is 14 1/2 years.

The zoo euthanized another tiger, named Charlie, in early September at the age of 16. That tiger had lung cancer.

The zoo says Boris was the oldest Amur tiger in the Association of Zoos and Aquariums Species Survival Plan.

Sexson said the zoo will coordinate efforts with the Tiger SSP to eventually acquire another tiger. But for now, the zoo will use the available den space for its lion cubs.

Amur tigers, formerly called Siberian tigers, are a critically endangered species.