LONDON, ENGLAND - JANUARY 04:  A ring tail lemur plays with an abacus during the annual stocktake of animals at ZSL London Zoo on January 4, 2016 in London, England. The zoo's annual stocktake requires keepers to check on the numbers of every one of the 800 different animal species, including every invertebrate, bird, fish, mammal, reptile, and amphibian.  (Photo by Carl Court/Getty Images)