Gus, the beloved Central Park Zoo polar bear whose "depression" made headlines, died at age 27 yesterday.

The Wildlife Conservation Society explained, "Gus was euthanized yesterday while under anesthesia for a medical procedure conducted by WCS veterinarians. Gus had been exhibiting abnormal feeding behavior with low appetite and difficulty chewing and swallowing his food. During the procedure, veterinarians determined Gus had a large, inoperable tumor in his thyroid region. A necropsy will be conducted to determine the full pathology of the condition." The WCS adds, "The median life expectancy for a male polar bear in zoos is 20.7 years, according to the Association of Zoos and Aquariums."

Gus was not a native New Yorker: He was born at the Toledo Zoo in 1985 and arrived at the Central Park Zoo in 1988. In 1994, Gus became a media darling when it was noticed that he swam endless laps in his pool. It was determined that he was bored, so the zoo developed an enrichment program for him, which, the WCS says, "included providing moveable items for him to manipulate, implementing positive reinforcement training sessions, and having Gus forage for food to keep his mind and body active and healthy."

He had a great time with his companion Ida, but Ida died in 2011, raising concerns that he was depressed once more.

Jim Breheny, WCS Executive Vice President of Zoos and Aquarium, "Gus was an icon at the Central Park Zoo and a great source of joy for our visitors and staff. He was an important ambassador for his species bringing attention to the problems these bears face in the wild due to a changing environment. 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 really did love swimming in his pool—here's some footage we took last year:

The Wildlife Conservation Society estimates that 20 million people saw Gus.