A polar bear cub snuggles up against her mother Valeska, in their enclosure at Bremerhaven's (Bremen's) Zoo by the Sea, Germany March 9, 2016. The female cub, who is yet to ne named, was born on December 11 last year. (Photo by Carmen Jaspersen/Reuters)

A white Bengal tiger cub plays with its mother in a zoo in the Siberian city of Novosibirsk, about 2,800 kilometers (1,750 miles) east of Moscow, Russia, Tuesday, April 21, 2015. Two blue-eyed Bengal tiger cubs were born in March to a couple of white tigers at Novosibirsk zoo. (Photo by Ilnar Salakhiev/AP Photo)

14 week-old twin polar bear cubs play during their first presentation to the media in Hellabrunn zoo on March 19, 2014 in Munich, Germany. The male and female twins were born on December 9, 2013 in the zoo. (Photo by Alexandra Beier/Getty Images)

Bao Bao, the Giant Panda cub is seen by the media for the first time January 6, 2014 inside his glass enclosure at the Smithsonian's National Zoo in Washington, DC, a few days before going on display to the general public. Bao Bao was born at the Smithsonian's National Zoo August 2, 2013. (Photo by Paul J. Richards/AFP Photo)

Three-month old cheetah cubs make their public debut at the Smithsonian National Zoo on July 24, 2012 in Washington, DC. (Photo by T.J. Kirkpatrick)

A white Bengal tiger cub born in captivity is seen during a press presentation at Huachipa's private zoo in Lima, Peru, March 16, 2016. (Photo by Mariana Bazo/Reuters)

Gaza authorities say two newborn lion cubs just unveiled by Hamas as prized additions in a zoo they run have died. Mohammad Abdel-Rahman, the acting manager of the Beit Lahiya zoo in northern Gaza, said Thursday the cubs died of an unspecified illness. He said the zoo's staff was unable to save them because they lacked experience in caring for newborn cubs. Photo: Two-day-old lion cubs Fajr and Sjel are fed at a zoo in the northern Gaza Strip town of Beit Lahia, on November 19, 2013. (Photo by Mohammed Abed/AFP Photo)