Zookeeper Grant Kother, at ZSL London Zoo, weighs and measures a giant tortoise during the 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)

Meerkats are weighed and measured during the ZSL London Zoo 's annual weigh-in on August 22, 2012 in London, England. (Photo by Oli Scarff)

Zookeeper Don McFarlane, at ZSL London Zoo, weighs and measures an African Millipede during the Zoo's annual weigh-in on August 22, 2012 in London, England. (Photo by Oli Scarff)

“Elton” the spectacled owl is weighed and measured during ZSL London Zoo's annual weigh-in on August 22, 2012 in London, England. (Photo by Oli Scarff)

Zookeeper Vicky Fyson, at ZSL London Zoo, weighs and measures penguins during the Zoo's annual weigh-in on August 22, 2012 in London, England. (Photo by Oli Scarff)