London Zoo opens gates to colony of snappers for annual animal census Meerkats at London Zoo are induced to clamber over a clipboard by a smattering of grubs during the annual stocktaking. Photograph: Ben Stansall/AFPGetty There were 50 extra reptiles at London Zoo on Thursday. It was the start of the zoo's annual stock-taking, when keepers undertake a week-long census, and the press had been invited in for the count of the more photogenic animals. The displays of animal behaviour would have fascinated a passing zoologist, especially the mating calls of the homo snapperiensis. Can you move, love, we can't see the meerkats. That's the worst place you could stand. The keeper takes it in good heart and carries on feeding the meerkats. The meerkats (official count 11), being meerkats, appeared to relish the attention. You cannot help feeling a bit sorry for the otters (official count nine) in the adjoining pen. While photographers surround the meerkats, the otter family - Dad died recently, leaving a widow and eight daughters - attract less of a gaggle. "It's all about charisma," says Amy Harris, the zoo's media manager. Some animals just have it, and the best way to judge is to look at children's faces when they first see them. Counting the number of lenses also works. Does the zoo really need to count its animals? Surely they know how many they have? "They're regularly counted," says Harris, "but under the terms of our licence we have to do an official count once a year." And if they find a tiger or tarantula gone awol? She laughs. Every day the keepers do their daily checks so there shouldn't be any shocks. "Each animal is microchipped," says Lucy Hawley, a keeper in the rainforest section, counting the Asian short-clawed otters, a breed threatened by habitat loss and classed as vulnerable by the International Union for the Conservation of Nature. Many of the animals' chips are checked during the count but not those of the otters; they are too hard to catch. After the otters, Hawley moved on to the monkeys and sloths. How does a sloth feel about having its microchip checked? "They're fine," she says. As long as you give them something to eat and tickle their tummies. In the bug house Amy Callaghan, an invertebrates keeper, is getting a red-kneed bird-eating spider (aka tarantula) called Jill out of her box. "Can you put it on the clipboard?" chorus the photographers. "I don't want to stress her out too much," says Callaghan. Eventually Jill - the tarantulas (official count 35) are named after ex-members of the zoo's press team - obliges. She's fine now. You get warning signs if there's a problem. She'll flick her back legs if she's unhappy. Remember that, if you ever encounter a red-kneed tarantula. Spiders unquestionably offer a career with legs, but were they really her vocation? "I used to work in aquatics and I was never that keen on them before I came here," admits Callaghan. My parents couldn't believe it. They said 'you're terrified of spiders and flies'. But when I started working with them I soon came to appreciate them. They have their own personalities. Jill is very docile. Jill behaves beautifully, but not all the animals respond well to the spotlight. The black-capped Bolivian squirrel monkeys (23 of those) will not stay still for the cameras. "They're usually very good," says their keeper, "but they're a bit freaked out at the moment." There are ropes running across the top of their enclosure, and as the monkeys scamper across they send a shower of shit down on the photographers. The penguins (official count 59) are also uncooperative, refusing to stand next to a naff sign that says "Line up here to be counted." "They're all buggering off," complains a photographer as the birds lose interest in the fish being thrown to them. But one penguin, destined for stardom, saves the day by trying to eat the keeper's clipboard. Some species are harder to count than others. The aquarium is a challenge: fish do not stop swimming to be counted so the keepers take a photograph of the tank and base their count on that. Partula snails - tiny, well camouflaged and hidden under leaves - are also tricky, but they are critically endangered so the zoo makes a point of counting every one. "We've got hundreds," says the zoo's director, David Field. But they're an incredibly endangered species so we count them individually. We are looking to reintroduce them in the wild, and knowing the precise number we have is crucial. The zoo has to draw the line somewhere, however, and leafcutter ants is as good a place as anywhere. It does not attempt to count them individually. "We cheat," says a press officer. We think we have about 10,000, but we just count them by colony. This first day of counting is largely for the cameras, but, says Field: "The data has real scientific integrity. It's used by researchers to assess the longevity and health of the animals. We produce an inventory, and zoo inspectors can then come in and check everything that's going on. Have they ever discovered they'd lost part of the collection? Field says: "We might sometimes find that we'd got one individual which we thought we'd moved somewhere else, so the individual identifications can sometimes differ, and we might find counts differ with the odd invertebrate and fish species. But when you've got things like the penguins and some of the larger species like our gorillas (official count three), we don't tend to lose those.