Gus, the polar bear who became one of the most popular faces of the Central Park Zoo due to his anxious behavior, was euthanized on Tuesday after a veterinarian found a large, inoperable tumor in his thyroid.

Gus began showing signs of depression after his mate, Ida, died two years ago, but zoo officials noticed changes in him in the ’90s, when he began swimming laps obsessively in his habitat for extended periods. His caretakers say he would sometimes swim for up to 12 hours in a single day.

“It’s too repetitive. The first thing you worry about is whether this reflects some deep-seated physical problem. Is he losing weight? Is his appetite off? Is his behavior toward the ladies he’s living with declining?” said Dr. William Conway, former general director of the Wildlife Conservation Society.

Gus was soon analyzed by experts, who said his behavior stemmed from boredom. His habitat was immediately redesigned and he was given the opportunity to forage for his own food rather than being fed, as he would do in the wild. Soon, his obsessive swimming patterns tapered off. But recently, Gus began to exhibit problems with chewing his food and swallowing, and zoo officials had him examined to determine if the issue was psychological or physical. After tests showed the tumor, the decision was made to put him down.

“He was an important ambassador for his species bringing attention to the problems these bears face in the wild due to a changing environment,” Jim Breheny, the society’s executive vice president of zoos and aquariums, said in a statement. “Polar bears are apex predators – the kings of their domain, but vulnerable in a world affected by climate change brought on by human activity.”

Gus will be sorely missed by both his caretakers and those who visit the zoo, as he was an iconic part of the community.

“He was the iconic image for Central Park,” said Breheny. “Some of my favorite images were seeing Gus in his exhibit with the New York cityscape behind him. It was surreal.”

Image: Wikimedia Commons, Central Park Zoo