One of New York City's most beloved animals has passed away this week. Gus, a world-famous polar bear at New York's Central Park Zoo had to be euthanized on Tuesday after veterinarians discovered an inoperable thyroid tumor during a medical exam.

"Gus was an icon at the Central Park Zoo and a great source of joy for our visitors and staff," said Jim Breheny, executive vice president of the Wildlife Conservation Society, which operates the zoo. "He was an important ambassador for his species, bringing attention to the problems these bears face in the wild due to a changing environment."

Gus, who was 27-years-old, was a staple at the zoo. His fame grew wildly back in 1994, when he began to receive a large amount of attention for his peculiar swimming habits. Gus would often spend 12 hours a day swimming in a figure-8 pattern in his pool, and his handlers were stumped over what could cause such a regimented lifestyle.

"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?" queried Dr. William Conway, then the general director of the Wildlife Conservation Society.

Word began to spread about Gus' peculiar routine and soon people from all over the world were wondering about just what had gotten into the polar bear. The zoo eventually flew in an expert to analyze why Gus was acting so strangely. His conclusion? Boredom.

With that in mind the Central Park Zoo began to give Gus an array of interesting activities to stimulate his attention and imagination. His handlers would hide his food so he would have to forage for it, provide numerous toys for him, and partake in positive-reinforcement training sessions with the bear.

Though Gus never completely broke his habit of repetitive swimming, it did slow down considerably once he was given more interesting activities to do. He soon became a fixture at the Central Park Zoo, and it's estimated that 20 million visited Gus while he was in captivity there.

"It's heartbreaking staring at the empty tank. It's terrible, but what can you do? There aren't many polar bears left," said Sean Stewart, 31, of Queens. "It's a real shame. I'm very disappointed."

New York City now only has one polar bear left, Tundra, who is 22-years-old and is kept at the Bronx Zoo. The Central Park Zoo is conducting a necropsy on Gus and will eventually cremate his body. Zoo officials are still not sure if they will be able to purchase a new polar bear from another zoo.