Soosha takes an interest in a photographer using the underwater observation area. The 25-year-old polar bear came to Denver in 1987. (Denver Post file)

A 25-year-old polar bear at the Denver Zoo was euthanized last week because of "severe" declining health, zoo officials announced Tuesday.

Soosha, a female bear, "began to show increased joint pain, decreased mobility and lethargy the past few months," the Denver Zoo said in a statement. "Although she received medications for her joint pain, she did not return to her normal self."

Eventually, Soosha began declining food and quit eating.

"It is always difficult to make this type of decision," Dr. Scott Larsen, the zoo's vice president of veterinary medicine, said in the statement. "As hard as it is, this was the right thing to do."

The typical longevity of polar bears is 20 to 25 years, the zoo said.

Multiple

View photos of polar bear Soosha's life at the Denver Zoo.

In 1987, Soosha arrived in Denver from Riverbanks Zoo in Columbia, S.C., and she was one of the first residents of the Northern Shores exhibit.

The Denver Zoo remains home to Soosha's niece, Cranbeary, and Cranbeary's mate, Lee.

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Denver Zoo polar bear Soosha euthanized