The weight is over for all creatures great and small as they have been sized-up in London Zoo's annual weigh-in. Silverback gorillas, rare baby crocodiles, big owls and tiny snails were among the animals stepping on to the scales. As well as being an indicator of an animal's general wellbeing, regular weight checks and waist measurements also help zoo keepers detect pregnancies of endangered species.
The keepers spend hours each year taking the vital stats of the animals in their care, but they have to get creative when it comes to encouraging the animals to be measured up - from tempting tortoises to climb on to a scale to persuading flighty birds to stand still on a customised perch.
Figures are recorded into the Zoological Information Management System (ZIMS), a database shared with zoos around the world, helping zoo-keepers to compare information on thousands of endangered species. Nathan Coles, a senior keeper at ZSL London Zoo, weighed Max, a Eurasian eagle-owl, the largest species of owl in the world. "We weigh him everyday to get an accurate record of what he weighs," he said, adding: "That allows us to work out how much food he needs on a daily basis."
Luke Harding, a qualified keeper in the reptile department, was tasked with weighing an "incredibly rare" species of crocodile that was hatched at the zoo in June. "At this age these guys are really secretive feeders, so as babies they're really shy. So one of the best ways for us to tell that everybody within the group is eating well and growing well is to take regular weights," he said.