London Zoo begins its annual census of all creatures great and small

Animals stood up to be counted — or in some cases swam, crawled or flew — as London Zoo began its annual census.

Zookeepers with cameras, calculators and clipboards counted critters Monday, the start of a weeklong campaign to record every resident mammal, bird, fish, invertebrate, reptile and amphibian.

The zoo is home to 17,500 animals of more than 750 species, from silverback gorillas to tiny leaf-cutter ants. New arrivals in the past year include a baby Western lowland gorilla and a litter of African hunting dog pups.

Ants and other extremely tiny creatures are counted in colonies, but all others are recorded individually.

The annual stock-taking is required under the license terms of British zoos. The data is used for zoo management and international breeding programs for endangered animals.