Knut, the polar bear, died in front of hundreds at the Berlin Zoo two weeks ago, but the cause of his death was unknown. Experts now say he drowned after falling into a pool.
The 4-year-old polar bear had brought happiness to many visitors and even landed on the front cover of Vanity Fair magazine in 2007.
Budapest Zoo's 18-year-old polar bear, Vitush, plays with a ball in his pool in Budapest, Hungary, Feb. 5, 2009.
Giant Panda 'Kai Kai' sits in his enclosure at the Giant Panda Forest exhibit at the River Safari, Nov. 28, 2012, in Singapore. Panda populations are threatened by poaching and a loss of habitat, as well as a low birth rate.