London Zoo on Wednesday carried out its annual weigh-in as it sought to keep track of more than 17,000 animals in its care.
Ten-week-old penguin chicks and 80-year-old tortoises were among a huge variety of animals that had their vital statistics recorded at the zoo in London's Regents Park.
Each measurement is recorded in the Zoological Information Management System (ZIMS), a database shared with zoos all around the world, helping zookeepers to compare important information on thousands of endangered species.
"With different behaviours, personalities and traits to take into consideration, zookeepers use ingenious tactics to entice the animals in their care to stand up and be measured," said an official from the Zoological Society of London (ZSL).
Methods used include "getting penguins to walk over scales as they line up for their morning feed and training tortoises to clamber onto scales hidden in their grassy paddock".
As well as a key gauge of the animals' general well-being, keepers can also use regular weight checks and waist measurements to identify pregnant animals, many of which are endangered species that are part of the zoo's international conservation breeding programmes.
Founded in 1826, ZSL is an international charity aiming to promote worldwide conservation of animals and their habitats.
As well as running London and Whipsnade zoos in England, ZSL has conservation projects in more than 50 countries. AFP