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)

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)

National Geographic photographer Steve Winter has spent most of his adult life shooting wild cats. Photo: A 14-month-old cub, cooling off in a pond, is riveted by a deer that appeared near the shore. Tigers are powerful swimmers; they can easily cross rivers four to five miles wide and have been known to swim distances of up to 18 miles. (Photo by Steve Winter/National Geographic)

Karis, an 8 week old lion cub, growls at a pumpkin as she explores a Halloween treat put in her enclosure by staff at Blair Drummond Safari Park near Stirling, Scotland, Tuesday, October 29, 2013. (Photo by Andrew Milligan/AP Photo/PA Wire)

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)

Indonesian motorists push their motorbikes as they wade through a flooded street outside the presidential palace in Jakarta, Indonesia, 09 February 2015. Incessant rain overnight triggered widespread flooding in the Indonesian capital Jakarta, bringing traffic to a standstill. The city hall in central Jakarta and the front lawn of the presidential palace were inundated in up to 20 centimetres of water, television pictures showed, after heavy rain. (Photo by Mast Irham/EPA)

A police cadet casts her vote in the presidential election in Moscow, Russia, Sunday, March 18, 2018. Vladimir Putin headed to an overwhelming win in Russia' s presidential election Sunday, adding six years in the Kremlin for the man who has led the world' s largest country for all of the 21 st century. (Photo by Pavel Golovkin/AP Photo)

A giant panda cub is pictured in an incubator at the Ya'an Bifengxia Giant Panda Breeding and Research Center in Ya'an city, southwest China's Sichuan province, 21 August 2015. Ten tiny panda cubs made their first public appearance at China's Ya'an Bifengxia Giant Panda Breeding and Research Center in southwestern Sichuan province on Friday (21 August 2015). All of the ten giant pandas were born in 2015. The oldest of them is just two month old, while the youngest one was born a week ago. This marks the first time they were put together as a group since they were born. (Photo by Imaginechina/Splash News)