LONDON (Reuters) – Keepers at London Zoo began the arduous task of counting some 600 different species on Thursday, carrying out the park’s week-long annual stocktake.

From tigers to monkeys, the zoo keeps records of all animals great and small as a requirement of its license. Last year, it recorded 19,289 animals.

“We have a lot of different species and within each species we have a lot of different individuals with different behaviors,” Animal Operations Manager Angela Ryan said. “So being able to make sure that we can see them, that we don’t double count them, can be quite challenging.”

New additions this year include penguin chicks, tamanduas and rescued leeches Buffy, Angel and Spike.

After the census is completed, the park will share the tally with other zoos around the world in a bid to aid international conservation programs.