All newborns and new arrivals have to be recorded in the annual audit
Zookeepers across the UK are counting every one of their animals and insects as part of a huge new year stock-take.
Every birth, death, new arrival and departure has to be recorded according to zoo legislation.
Local authorities then use the records to decide whether to issue and renew licences for zoos and aquariums.
The headcount makes January one of the busiest times for zoos. Bristol Zoo alone has some 450 different species to count from leaf insects to monkeys.
Over the past year, an orphan gorilla, a tiny turtle, a baby lemur, an armadillo and hundreds of tropical butterflies have arrived at the zoo.
Nigel Simpson, curator of birds, said the headcount could be tricky.
"Monitoring a growing penguin colony is important as we need to know who is who and, although the birds do have a unique spot pattern, they are not easily distinguished from one another."
The solution, he said, was to fit silicone bands on the penguins' flippers, each with a unique number so the penguins could be identified and counted.
Animal stock take at London Zoo
Once every UK zoo has counted their collections, the data is submitted to the British and Irish Association of Zoos and Aquariums (Biaza), the national body for zoo management and animal welfare.
Biaza's director Dr Miranda Stevenson said the information was important for animal conservation and made it possible to design breeding programmes to save threatened species.
Last January, London Zoo counted 15,104 invertebrates, fish, birds, reptiles, amphibians and mammals.
The list included 612 cockroaches, 57 Madagascar golden frogs, 41 blackfooted penguins, two lions and one giraffe.