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)

Rosie the elephants proves to be heavier than her companion and tips the park bench when she tries to sit down. (Photo by Mike Lloyd/Getty Images). 1977

A baby bush-baby in a set of scales at London Zoo shortly after birth. (Photo by Fox Photos/Getty Images). 10th August 1938

“Sniff out the Appenzell Cheese”. Alexander Hunter, 30, of Greenwich, Conn., took this photo in Appenzell, Switzerland, in September 2014. (Photo by Alexander Hunter)

A hyena cub got a mouthful from his mum after it appears he got a right telling off. Michael Raddall, a animal enthusiast and wildlife photographer from South Africa, snapped the mum and cub at the Timbavati game reserve in South Africa while on safari at the Umlani Bush camp. (Photo by Michael Raddall/Caters News Agency)

“The Baja California Pronghorn or Peninsular Pronghorn (Antilocapra americana peninsularis) is a critically endangered pronghorn, endemic to Mexico. The wild population is estimated at 200”. – Wikipedia

Photo: Two rare Peninsular pronghorns, male twins was born at the Los Angeles Zoo on April 24, 2009 in Los Angeles, California. Only 250 antelope-like Peninsular pronghorns are believed to exist in the wild. (Photo by David McNew/Getty Images)

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