Kirsty Wigglesworth / AP

A muddy bullfrog is inspected during a photo call for the annual census at the London Zoo on Jan. 3, 2013.

More than 17,500 animals, including birds, fish, mammals, reptiles and amphibians are counted in the annual census at the London Zoo. The count is a compulsory part of the zoo's license and the information is used for managing international breeding programs of endangered animals. 

Luke Macgregor / Reuters

Zoo keeper Zuzana Matyasova poses with penguins during the annual cataloguing of animals at the London Zoo.

Luke Macgregor / Reuters

Zoo keeper Jeff Lambert poses with leaf insects.

Ben Stansall / AFP - Getty Images

A European Eagle owl during the annual census at the London Zoo.

Luke Macgregor / Reuters

Zoo keeper Grant Kother poses with a Diamond Python.

Ben Stansall / AFP - Getty Images

Penguins swim during the annual census at the London Zoo.

Kirsty Wigglesworth / AP

A male jungle nymph sits on a female jungle nymph during a photo call for the annual census at the London Zoo.

Previously on PhotoBlog: 

• From the smallest to the tallest, zoo animals weigh in
• Bird lovers don disguises to save endangered sandhill cranes in Mississippi
• Camel prepares for turbulence
• 10-day-old baby flamingo makes appearance at zoo in Cali, Colombia

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Andrew Cowie / AFP - Getty Images

A zookeeper strokes a penguin on a scale during the annual weigh-in at London Zoo on Aug. 22.

Facundo Arrizabalaga / EPA

A meerkat climbs a scale on which another animal is already been weighed during the zoo's annual weigh-in at ZSL London Zoo, Aug. 22.

Andrew Cowie / AFP - Getty Images

A zookeeper measures Dirk the giant tortoise during the annual weigh-in at London Zoo on Aug. 22.

Oli Scarff / Getty Images

Giraffes are weighed and measured during the ZSL London Zoo 's annual weigh-in on Aug. 22.

Oli Scarff / Getty Images

Zookeeper Don McFarlane weighs and measures an African Millipede during the zoo's annual weigh-in on Aug. 22.

ZSL’s Zoological Director, David Field says: “We need to know the vital statistics of every animal at the Zoo – however big or small."

Zookeepers at the London Zoo are responsible for more than 16,000 animals, spending countless hours recording the weight and measurements of each and every animal, including penguins, meerkats, lions and owls.  The measurements are collated in the Zoological Information Management System, from which zoologists can use the data to compare information on thousands of endangered species.

“This information helps us to monitor their health, their diets and their general well-being. By sharing it with other zoos and conservationists, we can use this knowledge to protect wild animals, and use it to assess their health, their behaviours and even their ages,” said Field.

Facundo Arrizabalaga / EPA

Giraffes await to go out at the London Zoo, Aug. 22.

See more cute animals our our Animal Tracks slideshow

Toby Melville / Reuters

An Humboldt Penguin dives off a board as a heron stands in the background at London Zoo in London March 29, 2012. The diving board has been installed to coincide with 'Inspired by 2012' London Olympic program.

Kirsty Wigglesworth / AP

A Humboldt Penguin swims under water after taking a dive from the new Olympic London 2012 style diving board installed in the penguin enclosure at London Zoo, Thursday, March 29, 2012.

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