Five micropigs born to mother, “Truffel”, are seen in Zoo Wuppertal on August 11, 2014 in Wuppertal, Germany. The five micropigs are the major attraction of Zoo Wuppertal. Pigedy, Fiete, Frederik, Smartie are 4 males and is Keks is a female micropig. (Photo by Animal Press/Barcroft Media)

A life size animatronic Tyrannosaurus Rex dinosaur arrives at Bristol Zoo Gardens on May 14, 2012 in Bristol, England. Twelve animatronic dinosaurs arrived at Bristol Zoo Gardens this morning after being transported in crates from Texas, USA. They will form part of the zoo's summer exhibition “DinoZoo” which opens later this month. (Photo by Matt Cardy)

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 Common Blue Morpho butterfly lands on the arm of Garbiella as it and hundreds of other butterflies from around the world fill the bird aviary for the next month at the San Diego Zoo Safari Park in San Diego, California March 13, 2015. Called the Butterfly Jungle, the exhibit has over 30 species of butterflies. (Photo by Mike Blake/Reuters)

Nuninka, Bornean orangutan (Pongo pygmaeus), holds her newborn baby in the enclosure at Usti nad Labem Zoo, Usti nad Labem, Czech Republic January 3, 2017. (Photo by David W. Cerny/Reuters)

Twin baby panthers Remaong and Ferra cling to their basket while being presented to the media at Tierpark Berlin zoo on July 13, 2012 in Berlin, Germany. The two panthers were born in captivity on April 26. (Photo by Sean Gallup)

Meerkats are weighed and measured during the ZSL London Zoo 's annual weigh-in on August 22, 2012 in London, England. The height and mass of every animal in the zoo, of which there are over 16,000, needs to be recorded. The measurements are collated in the Zoological Information Management System, from which zoologists can use the data to compare information on thousands of endangered species. (Photo by Oli Scarff)

Zoo keeper Ross Poulter holds a White's Tree Frog in Edinburgh Zoo's new tropical forest zone on September 9, 2011 in Edinburgh, Scotland. The Brilliant Birds Exhibit which brings together beautiful and rare birds from all over the world is now more colourful and unusual, with the unveiling of the zoo's new tropical forest zone bringing together a collection of vertebrates, invertebrates and amphibians for the very first time. (Photo by Jeff J Mitchell/Getty Images)