London Zoo launches its trickiest annual task - the weigh-in

A porcupine stands on scales as zookeeper Chelsea Reid-Johnson poses during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville

LONDON (Reuters) - Bullfrogs, pythons and penguins were among creatures being coaxed onto the scales at London Zoo this week for the annual check on their weight and size.

The check-up allows keepers to assess the animals' general health, find out about pregnancies, when they are about to moult, and help to administer medicines according to their weight, the Zoological Society of London (ZSL) said.

The information is shared with zoos around the world by ZSL, a charity devoted to the worldwide conservation of animals and their habitats.

Zookeeper Unnar Aevarsson takes readings of an African bullfrog during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville

But actually getting animals to stand up and be measured is no easy task, involving for example tricking penguins into walking over scales as they line up for their morning feed or hanging breakfast from up high to encourage lions to reach up to their full height.

"We have to know the vital statistics of every animal at the zoo, from the tallest giraffe to the tiniest ant," said ZSL’s assistant curator of mammals, Teague Stubbington.

"It helps to ensure that every animal we look after is healthy, eating well, and growing at the rate they should - weight is a particularly important indicator of health and wellbeing."

A meerkat stands on scales as zookeeper Luke Taylor poses during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville

Not all the 19,000-plus animals across more than 560 species at London Zoo will be weighed: sometimes just one in a colony or group will be measured.

The annual weigh-in of animals, also including Asiatic lions, South African porcupines and South American coatis, will take a week to complete.

An African bullfrog sits on scales during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville

(Reporting by James Davey; eiting by Stephen Addison)

Zookeeper Martin Franklin poses as he encourages Humbolt penguins onto scales during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville

A meerkat stands on scales during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville

An Asiatic lioness looks for food next to a measuring stick placed during the annual weigh-in at London Zoo, London, Britain, August 22, 2019. REUTERS/Toby Melville