The oldest polar bear in the United States was put to sleep on Friday after a sudden deterioration in her condition, Philadelphia Zoo said.
Klondike, who at 34 was beyond the typical lifespan for her species, went downhill fast in the last two weeks, zookeepers said, including having difficulty standing and walking after lying down. She also recently had a urinary tract infection.
"We are very sad for this loss. Klondike was a very popular resident at Philadelphia Zoo," said Kevin Murphy, general curator.
"She received great care from her keepers and the veterinary staff during her long and very healthy life here. She will be greatly missed by our staff.
"In addition to the joy she brought guests over more than three decades, she has been an important ambassador to wild polar bears, who are increasingly threatened by climate change and resulting shrinkage of polar ice."
Philadelphia Zoo is home to an additional female polar bear, Coldilocks, who is also 34 and who arrived and lived with Klondike.
A typical lifespan for polar bears in zoos is about 24 years, according to the zoo.