Every gorilla, penguin and even each ant in London Zoo was being rounded up and counted as the attraction's annual census got under way on Thursday.
More than 850 species and thousands of individual animals have to be registered in the week-long stock take, which is required as part of the zoo's licencing agreement.
Some of the world's most endangered species were being counted for the first time, including the first spiny-headed lizards to be born in Britain.
Spectacled owls, oriental short-clawed otters, Humboldt penguins, jungle nymph insects and western lowland silverback gorillas were among the creatures logged in the census.
The data is shared with other zoos worldwide via the International Species Information System to spread knowledge and help with breeding programmes.
“All of the keeping staff at London are out with their animals and keeping an eye on how they have been over the last year,” said zoological manager Mark Habben.
“Any new births are recorded and we log all of that information so that it's accessible for other animal collections.
“2013 was a very successful year for us breeding-wise. We had our female tapir give birth so we have got a young tapir here on exhibit which is fantastic.” - Sapa-AFP