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Animals are weighed at London Zoo

Two monkeys, one on a table and one balanced on a stand on top of a scales. A man with long hair tied up, a beard, sunglasses, wearing a green t-shirt and blue disposable gloves. He is holding a clipboard which says London Zoo in one hand and holding the monkey's paw with the other.PA Media

London Zoo's annual weigh-in has begun.

The yearly event where keepers weigh thousands of animals can take up to a week to complete.

London Zoo's animals are weighed and measured regularly as a way of monitoring their health.

Their measurements are recorded in a global database called the Zoological Information Management System.

Scroll down to see how creatures big and small were weighed.

A capybara by a large stone nudges a weight monitor with its nose.PA Media

Capybaras originate from Northern and central South America

Two Capybaras are encouraged onto a weighing scale by a keeper.PA Media

London zoo's capybaras are called Gizmo and Kiwi

These capybaras have been encouraged to go on the scales with some fresh plants.

Kiwi weighed in at 45kg, while her brother Gizmo weighed 50.5kg.

It can take up to a week to weigh every mammal, bird, reptile, fish and invertebrate at ZSL London Zoo.

A katydid is weighed on a small kitchen scale.PA Media

A kitchen scale has been used for this katydid, the insect which looks just like a leaf measures up to 6cm long.

Bolivian squirrel monkey.PA Media

The zoo uses a variety of ways to get the animals on the scales including incorporating parts of their habitat.

This Bolivian squirrel monkey is happily balancing on a pole at the same time as being weighed.

A Vietnamese magnolia snail is weighed during the annual weigh-in at ZSL London Zoo in London.PA Media

One of these Giant Magnolia Land Snail weighed only 102.5g, about the same as a small apple.

A snail being weighed.ZSL

One of the smallest of the creatures to be weighed is this partula snail about the size of a finger nail

The conservation zoo cares for a range of species, including the tiny Partula snails, which weigh less than 1g.

Humboldt penguins surround a keeper who is weighing one on a blue set of scales. She is kneeling infront of a pool wearing a green t-shirt and black shorts. EPA

Keeper Jessica Ray weighs Humboldt penguins which usually live at sea and on rocky coasts in Chile and Peru

The animals are weighed as part of a yearly health check, it helps the zoo check on their development.

London Zoo's Animal Operations Manager Daniel Simmonds said:

"Regular weigh-ins help zookeepers track the health of our animals, including invertebrates like the magnolia land snails, the capybaras and Humboldt penguins, and genuinely help us manage the care of these animals, who play a vital role in our global conservation efforts."