Zookeeper Suzi Hyde counting Humboldt penguins during the annual stocktake at the ZSL London Zoo in London on Tuesday. Keepers at the zoo have begun the mammoth task of counting the park's more than 700 species, with some using treats to entice some animals out for the annual resident census. From small invertebrates to larger mammals, creatures of all sizes are counted at the zoo, which is located in the centre of the British capital. New additions for the 2017 census include four Humboldt penguin chicks and two Sumatran tiger cubs. Tallying up all the animals takes around a week and is a regulatory requirement. Information collected is then shared with other zoos around the world to help in the protection of endangered species. At last count, the zoo had more than 18,000 animals.