LONDON, ENGLAND – AUGUST 25: Zookeepers measure the length of a pueblan milk snake in the Reptile House of ZSL London Zoo as part of their annual weighing and measuring of their animals on August 25, 2011 in London, England. The heights and weights of over 750 different animal species at the zoo are recorded into the International Species Information System, to monitor their health and share the data with other zoos across the world. (Photo by Oli Scarff/Getty Images)