Two brown bear cubs born at Whipsnade Zoo. (Photo by Evening Standard/Getty Images). 1970

A zoo keeper feeds Diego, a three month old howler monkey, which is reared at Edinburgh Zoo, July 29, 2008 in Scotland. (Photo by Jeff J. Mitchell/Getty Images)

A gibbon drinks from a soft drink bottle, given by a tourist, at a zoo in Kunming, Yunnan province, June 18, 2015. (Photo by Wong Campion/Reuters)

Central Park Zoo, New York, 1967. (Photo by Garry Winogrand)

A tiger yawns next to a piglet at the Sriracha Tiger Zoo, in Chonburi province, Thailand, June 7, 2016. (Photo by Chaiwat Subprasom/Reuters)

A Grevy’s zebra gets itself noticed at ZSL Whipsnade Zoo in Whipsnade, England on April 20, 2018. (Photo by Tony Margiocchi/Barcroft Media)

A soldier eats ice cream as she visits a zoo in Pyongyang, North Korea, September 12, 2018. (Photo by Danish Siddiqui/Reuters)

An alpaca chewing a leaf is pictured on November 18, 2014 in the zoo of Frankfurt am Main, Germany. (Photo by Frank Rumpenhorst/AFP Photo/DPA)