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London Zoo completes 'monumental' Weigh-In Day - the best photos

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ZSL London Zoo annual weigh in giant tortoise
The scales creak as a giant tortoise steps on-board for his weigh-in. Picture: PA

By William Mata

London Zoo keepers have spent their day persuading hundreds of animals to get on the scales as part of their annual weigh-in.

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The Zoological Society of London weighs its animals almost every day, but made a special effort on Tuesday to record the mass of its capybaras, giant tortoises, and penguins.

Priscilla, a 30-year-old giant Galapagos tortoise, was lured onto a board scale with a lettuce snack while the Humboldt penguins jostled in line.

But the highest recorded weight was expected to be Molly the giraffe, who usually weighs about 700kg.

ZSL London Zoo annual weigh-in 2025: Capybaras
One at a time: Capybaras are persuaded to get onto the scale. Picture: PA
Lemurs at ZSL London Zoo Weight-In
Lemur or less: Some of the animals were trained to stand in position to be measured. Picture: PA
ZSL London Zoo weigh-in 2025 penguins
How much? Penguins get on the scale at the zoo's weigh-in. Picture: PA
ZSL London Zoo Weigh-in 2025 snail
Now it's in, how do we get it out? A snail takes part. Picture: PA

Daniel Simmonds, London Zoo’s animal operations manager, said: “This is a monumental task.

“We look to weigh as many of our animals as we can and log everything onto our database and then share that information with other zoos.”

Keepers helped tempt animals onto the scales with food and recorded the weight which will have an impact on their diets in the months to come.

Many of the zoo’s animals are trained to perch on a scale while zookeepers note down their measurements, while, for some, scales may be placed in doorways or disguised in their habitats, meaning the animal can be weighed without realising.

Mr Simmonds said that they are hoping for some animals, such as those that are pregnant or growing, to gain weight.

“[It] is not just about numbers on a scale,” he said.

“Our animals receive world-class care – and a huge part of this is our meticulous planning of their diets.

“Our zoo-tritionist ensures every animal is getting the nutrients they need, while our keepers devise ways to feed the animals that spark all of their natural instincts – keeping them fit and challenged.”