A polar bear fast asleep at London Zoo. (Photo by Fox Photos/Getty Images). 1961

A three-day-old Bengal tiger calf is cared for after being fed at the National Zoo in Masaya on August 30, 2021. A female Bengal tiger calf was born in the National Zoo of Nicaragua, the fourth of this species in risk of extinction born in captivity in the country, and is under special care due to a limited breastfeeding capacity of the mother. (Photo by Inti Ocon/AFP Photo)

A grey-bellied Night Monkey (Aotus Lemurinus) plays with a teddy bear at the veterinary clinic of the Cali Zoo in Cali, Colombia on January 27, 2020. They monkey is being raised by personnel of the Cali Zoo after a worker found it near the complex. Apparently it fall from a tree with his father who had health problems. (Photo by Luis Robayo/AFP Photo)

This photo provided by Running Press and Quarto, Inc. shows Feline Fox from the book, “Cats in Hats”, published by Running Press. The book released on March 24, 2015. (Photo by Liz Coleman/Running Press/Quarto, Inc. via AP Photo)

A young oriental small-clawed otter at the zoo in Neumuenster, Germany, March 5, 2014. The six young otters (one male, five female) were born on December 7, 2013. (Photo by Maja Hitij/EPA)

Female Chimpanzee “Fifi” eats carrots as she sits in her enclosure at Taronga Zoo on her 60th birthday May 21, 2007 in Sydney, Australia. Fifi is the oldest of the Zoo's chimp population, which consists of 19 individuals. (Photo by Ian Waldie/Getty Images)

A Geoffroy's Monk Saki is seen at the Parque de Las Leyendas zoo in Lima, Peru, February 14, 2018. (Photo by Guadalupe Pardo/Reuters)

A green iguana, or American iguana sits on an Aldabra giant tortoise, the largest tortoise of the world, in their enclosure at the zoo park of Lille, northern France, on February 11, 2019. (Photo by Philippe Huguen/AFP Photo)