A handout picture made available by the Sydney Wild Life Zoo shows 7-month-old kangaroo joeys, Dot and Matilda during their official public debut at the Sydney Wild Life Zoo, in Sydney, Australia, 18 December 2015. (Photo by EPA/Sydney Wild Life Zoo)





A heat-stressed koala waits as a resident pours water on its back on December 19, 2015 in Adelaide, Australia. Adelaide is experiencing an extreme heatwave, with temperatures reaching over 40 degrees for five consecutive days. (Photo by Morne de Klerk/Getty Images)





This May 19, 2015 photo provided by Artisan Books shows Piggy, a 2-year-old Boston Terrier, standing up to photographer Elias Weiss Friedman, in New York. Photos taken first for his blog, “The Dogist”, now have been collected in Friedman's new book of the same name. Friedman says it's important to make eye contact with a dog before you photograph it. And he doesn't like to put people in his photos, but sometimes they work well as background. (Photo by Elias Weiss Friedman/Artisan Books via AP Photo)





A sea lion performs at the Sunshine International Aquarium in Tokyo, December 22, 2015. (Photo by Hitoshi Yamada/NurPhoto via ZUMA Press)





A Bengal tiger licks a glass enclosure as a Filipino child reacts during the “Animal Christmas Party” at the Malabon Zoo in Malabon City, north of Manila, Philippines, December 21, 2015. The Malabon Zoo is one of the largest private collections of exotic and endemic animals in the Philippines. (Photo by Mark R. Cristino/EPA)





Red Howler Monkey (Alouatta caraya) babies are seen at the Hacienda Miraderos forests in the Municipality of Armenia, Antioquia, Colombia, December 14, 2015. (Photo by Fredy Builes/Reuters)





A volunteer holds a baby Red Howler Monkey (Alouatta caraya) at the Hacienda Miraderos forests in the Municipality of Armenia, Antioquia, Colombia, December 14, 2015. (Photo by Fredy Builes/Reuters)





A volunteer holds a baby Red Howler Monkey (Alouatta caraya) at the Hacienda Miraderos forests in the Municipality of Armenia, Antioquia, Colombia, December 14, 2015. (Photo by Fredy Builes/Reuters)





A baby Red Howler Monkey (Alouatta caraya) is seen at the Hacienda Miraderos forests in the Municipality of Armenia, Antioquia, Colombia, December 14, 2015. (Photo by Fredy Builes/Reuters)





Ginni, an Asiatic lioness, yawns inside its enclosure at Prague Zoo, Czech Republic, December 20, 2015. Picture taken through a window. (Photo by David W. Cerny/Reuters)





Anita, a 22-year-old female macaque, performs before children as part of the New Year and Christmas celebrations, in Barnaul, Russia, December 23, 2015. (Photo by Andrei Kasprishin/Reuters)





Chimpanzees play before their daily feeding at the Liberia Chimpanzee Rescue Project headquarters in Charlesville, Liberia, November 19, 2015. (Photo by Malin Palm/Reuters)





A chimpanzee named Samantha waits for her daily feeding at the Liberia Chimpanzee Rescue Project headquarters in Charlesville, Liberia, November 19, 2015. (Photo by Malin Palm/Reuters)





Chimpanzees eat fruit at the Liberia Chimpanzee Rescue Project headquarters in Charlesville, Liberia, November 19, 2015. (Photo by Malin Palm/Reuters)





A chimpanzee eats at the Liberia Chimpanzee Rescue Project headquarters in Charlesville, Liberia, November 19, 2015. (Photo by Malin Palm/Reuters)





Young Lynx wait to be fed in their enclosure at the Highland Wildlife Park on December 16, 2015 in Kincraig,Scotland. Concerns have been raised by Scottish landowners in over proposals to reintroduce Lynx back into the ecosystem in the wilds of Scotland. The Lynx UK Trust has been asking Scottish Land and Estates groups, their views on bringing the wild cat back into trial sites in Aberdeenshire, Argyll, and the Borders. (Photo by Jeff J Mitchell/Getty Images)





A Bornean male orangutan is pictured at the zoo in Usti nad Labem, Czech Republic on December 17, 2015. (Photo by Slavek Ruta/Shutterstock/Rex Features)





A newly released on December 14, 2015 photograph of two tiger cubs born on 29 November in Sydney, Australia. (Photo by Dreamworld/Xinhua Press/Corbis)





A lemur opens a Christmas package filled with food on December 23, 2015 at the zoo in La Fleche, northwestern France. (Photo by Jean-Francois Monier/AFP Photo)





A group of lemurs prepare to open a Christmas package filled with food on December 23, 2015 at the zoo in La Fleche, northwestern France. (Photo by Jean-Francois Monier/AFP Photo)





Grizzly bear cubs, Juneau & Sitka, stand during their first day out in the public at the Palm Beach Zoo on December 17, 2015 in West Palm Beach, Florida. The Zoo will host the two-orphaned female grizzly bear cubs until their new permanent home in a South Dakota zoo is completed. (Photo by Joe Raedle/Getty Images)





In this December 20, 2015 photo released by the Monterey Bay Aquarium, a Sea Otter holds its newborn pup in Monterey Bay Aquarium Tide Pool in Monterey, Calif. The aquarium posted news of the birth online this weekend, along with adorable photos of the fuzzy brown pup playing with mom. (Photo by Tyson V. Rininger/Monterey Bay Aquarium via AP Photo)





A seabird (common tern) gets out the water in the Mediterranean Sea, in the French Riviera city of Nice, southeastern France on December 18, 2015. (Photo by Valery Hache/AFP Photo)





A California sea lion catches a fish thrown by its keeper in the enclosure in the zoo in Stuttgart, southern Germany, Friday December 18, 2015. (Photo by Marijan Murat/DPA via AP Photo)





A handout picture made available by Tourism and Events Queensland on 24 December 2015 shows Bon Bon, a 12-month-old koala, celebrating with Christmas decorations at the Rainforestation Nature Park in Cairns, Australia, 23 December 2015. (Photo by EPA/Tourism and Events Queensland)





A Squirrel monkey(Saimiri Sciureus) bites into a star-shape piece of watermelon on a tree's branch at an enclosure of the zoo in Cali, Colombia, 22 December 2015. As the animals are currently suffering from a heat wave in the region, they very much enjoy the juicy fresh fruit to quench their thirst. Cali's Zoo in the recent days received some Christmas presents including vegetables, ice creams, honey and relaxing essences. (Photo by Juan Carlos Quintero/EPA)





A squirrel looks out of a birdhouse loaded with sunflower seeds, in Muelheim, Germany, 17 December 2015. Instead of gathering and burying nuts for the winter months, squirrels apparently find it easier to steal feed left for birds. (Photo by Roland Weihrauch/EPA)





A grey seal pup lies in a pool at the seal station in Friedrichskoog, Germany, 21 December 2015. The pup is raised at the station after it became seperated from its mother. (Photo by Wolfgang Runge/EPA)





Grizzly bear cubs, Juneau & Sitka, enjoy their first day out in the public at the Palm Beach Zoo on December 17, 2015 in West Palm Beach, Florida. The Zoo will host the two-orphaned female grizzly bear cubs until their new permanent home in a South Dakota zoo is completed. (Photo by Joe Raedle/Getty Images)





In this photo taken December 14, 2015, animal keeper Stacey Tabellario holds Bei Bei, the National Zoo's newest panda and offspring of Mei Xiang and Tian Tian, as he is presented to members of the media at the National Zoo in Washington. The youngest giant panda cub at the National Zoo is ready for his close-up. Bei Bei will make his public debut on Jan. 16. During an audience with a small news media contingent Monday, he was so relaxed that he fell asleep and drooled on an examination table. At nearly 4 months old, Bei Bei weighs more than 17 pounds and is gaining about a pound a week. He's bigger than his older siblings were at the same age. (Photo by Andrew Harnik/AP Photo)





Mabel, a 2-month-old pygmy hippopotamus calf, appears with her mother, Chomel, at the Henry Doorly Zoo in Omaha, Neb., Tuesday, December 22, 2015. Pygmy hippos are native to western Africa swamps and rain forests. The International Union for Conservation of Nature lists the species as endangered. (Photo by Nati Harnik/AP Photo)





Bei Bei the giant panda cub is held by it's mother, Mei Xiang in an enclosure at the Smithsonian National Zoological Park on Tuesday December 15, 2015 in Washington, DC. He was born August 22, 2015. (Photo by Matt McClain/The Washington Post)





Inuka, the first polar bear born in the tropics, enjoys an ice cake during its 25th birthday celebrations at the Singapore Zoo December 16, 2015. The locally born and bred polar bear turns 25 on Boxing Day this December. (Photo by Edgar Su/Reuters)





This undated image released by McMaster University, shows a new species of African clawed frog. Scientists have discovered six new kinds of African clawed frog, and added back another to the list, boosting the number of known species by 30 percent and offering new avenues for research on human disease, said a study on December 16, 2015. The creatures are “most widely studied amphibians in the world”, and now there are 29 known clawed frog species instead of just 22, according to the study in PLOS ONE. African clawed frogs share a close evolutionary relationship with humans and are often used in biomedical research, including those involving genetic studies and cancer. The amphibians sport unusual claws on their first three toes, and reside in slow moving or stagnant water in west and central sub-Saharan Africa. (Photo by Vacute Gvocaron/AFP Photo/McMaster University)