A one-month-old wolf cub ululate as zookeeper Luo Yong plays guitar at the Chongqing Yongchuan Safari Park on March 27, 2008 in Chongqing, China. Luo has worked as a keeper in the wolf zone of the park after he graduated university. Luo has developed a special way to communicate with the wolves by trying to imitate the noises they make. He also teaches wolf cubs to ululate and some wolves will howl along when he plays guitar. (Photo by China Photos/Getty Images)

This Saturday, July 22, 2017 photo released by Tokyo Zoological Park Society, shows a giant panda cub at Ueno Zoo in Tokyo. The baby panda, born in June, got a check up on Saturday. (Photo by Tokyo Zoological Park Society via AP Photo)

A newly born Mexican gray wolf cub, an endangered native species, is seen at its enclosure at the Museo del Desierto in Saltillo, Mexico, July 19, 2016. Though once held in high regard in Pre-Columbian Mexico, it is the most endangered gray wolf in North America, having been extirpated in the wild during the mid-1900s through a combination of hunting, trapping, poisoning and digging pups from dens. (Photo by Daniel Becerril/Reuters)

Giant panda Mei Xiang discovers a birthday cake meant for her cub Bei Bei (NP) who turns one at the Smithsonian National Zoo in Washington, DC on August 20, 2016. (Photo by Linda Davidson/The Washington Post)

Children, wearing traditional Bavarian folk costumes specific to their region, prepare for the competition in the “Schuhplattler” style of Bavarian folk dancing for the Bavarian Lion Award at the Huosigau Heimat and Folklore Society on May 28, 2011 in Weilheim, Germany. (Photo by Johannes Simon/Getty Images)

A family of children share a bath in Japan, circa 1965. (Photo by Three Lions/Hulton Archive/Getty Images)

Burdened with a shawl full of her belongings, a woman stops for a rest on the road between Julaca and Puno in Peru. (Photo by Three Lions/Getty Images). Circa 1955