

Budapest Zoo's 18-year-old polar bear, Vitush, plays with a ball in his pool in Budapest, Hungary, Feb. 5, 2009. Bela Szandelszky/AP
Triton strikes a pose for visitors to the Roger Williams Park Zoo in Providence, R.I., in July 1999. Melanie Stetson Freeman/Staff/FILE
Polar bear cub Wilbaer plays in the outdoor enclosure at the Stuttgart zoo in southern Germany, in April 2008. Daniel Maurer/AP/FILE
A mother protects her cubs in Wapusk National Park on the shore of Hudson Bay near Churchill, Manitoba, Canada, in November 2007. Jonathan Hayward/The Canadian Press/AP/FILE
Tourists crowd behind a glass wall to see a polar bear at a newly opened ocean park in Chengdu, China, on Aug. 26. AP
Vitus, an 18-year-old male polar bear, shakes off water on a sweltering day at the Budapest zoo on July 16. Laszlo Balogh/Reuters
Three-month-old Flocke plays at the Tiergarten Nurenberg zoo in Nuremberg, Germany, in April 2008. Andreas Beil/AP
Huggies carries one of her two newborn cubs at the Ouwehands Zoo in Rhenen, Netherlands, in March 2009. Michael Kooren/Reuters/FILE
Antonia swims in the Zoom Erlebniswelt amusement park in Gelsenkirchen, Germany, on July 20. Clemens Bilan/AP
Zookeeper Thomas Doerflein shares a moment with polar bear cub, Knut, during Knut's first public appearance at the Berlin Zoo in March 2007. Herbert Knosowski/AP/FILE
A polar bear has a bucket on his head, while a cub swims nearby in the cooling waters of Moscow Zoo on July 21 as a heat wave hit central Russia breaking temperature records. Misha Japaridze/AP
Kap relaxes in the Neumuenster Zoo in northern Germany on Jan. 6. Heribert Proepper/AP
Zookeeper Harald Hager bottle-feeds polar bear cub Flocke at the Tiergarten Nuernberg Zoo in Germany in January 2008. Ralf Schedlbauer/AP
Flocke plays in her enclosure with her keeper as she experiences the open air for the first time in March 2008. Ralf Schedlbauer/AP/FILE
A polar bear is pictured underwater at the zoo in Gelsenkirchen, Germany, in December 2009. Martin Meissner/AP/FILE
Twin 6-month-old polar bear cubs play in the city zoo in St. Petersburg, Russia, on March 25. Alexander Demianchuk/Reuters
A polar bear sprawls out in the snow, by a holiday-themed gift filled with bear treats, in December 2009 at the San Francisco Zoo in California. George Nikitin/AP
A collared polar bear walks with her cub on the ice in Alaska in this undated photo from the US Geological Survey. Steven Amstrup/US Geological Survey/AP
Charly, a 1,150-pound polar bear with a jack-o'-lantern, is seen at SeaWorld San Diego's Wild Arctic attraction. Mike Aguilera/SeaWorld San Diego/AP
Charly sleeps in SeaWorld San Diego in California on Aug. 27. Bob Couey/SeaWorld San Diego/AP
A polar bear rests at the zoo in Prague, Czech Republic, on Sept. 9. Petr David Josek/AP
Knut plays in the water on Sept. 4 in the Berlin zoo in Germany Maya Hitij/AP
A polar bear is seen underwater at the zoo in Gelsenkirchen, Germany, in December 2009. Martin Meissner/AP/FILE