Garnet, the 18 year old mountain lion at the New York State Zoo at Thompson Park, died Monday.

Animal care and veterinary staff at zoo euthanized puma, who had been suffering from age-related illnesses and diabetes.

In 2010, he began to exhibit signs associated with old age, including arthritis and renal failure.  

Last March, tests indicated he also had diabetes. 

Garnet was taken off exhibit during his treatment and zoo officials said he showed signs of improvement for a number of months.

However, in the past few weeks, the zoo said the cougar's health deteriorated and his condition became a quality of life issue.

Garnet had been a resident of the zoo for 18 years. 

He arrived in Watertown in 1993 after Department of Environmental Conservation seized him from a person who illegally had him as a pet.

The zoo director at the time, Don Moore, hand-raised Garnet. 

During his early years, he was well known for making appearances at local schools in zoo outreach programs. 

Pumas, which are found throughout the United States, southern Canada, Central and South America, go by many names including mountain lions, cougars, catamounts, mountain cats and panthers. 

They have a lifespan of 8-12 years in the wild.

According to Michelle Schireman, AZA Felid TAG Puma SSP Coordinator, Garnet appeared to be the oldest living mountain lion in the country. 

The use of insulin to treat diabetes in this species is still emerging. 

As more large cats age, the interest in geriatric veterinary medicine continues to grow.

The New York State Zoo hopes to present Garnet's treatment plan to colleagues at an upcoming Felid Taxonomic Advisory Group meeting so that his story may benefit others.