The London Zoo, which has more than 14,000 animals, conducted its annual weigh-in this week, an event that helps keep records on their health and other data up-to-date and measures the animals’ well being.

While zookeepers measure the animals throughout the year, every August they double-check all the information and invite news organizations to have a look.

“Having this data helps to ensure that every animal we care for is healthy, eating well, and growing at the rate they should,” Angela Ryan, the London Zoo’s head of zoological operations, said in a statement. “We record the vital statistics of every animal at the zoo — from the tallest giraffe to the tiniest tadpole.”

The zoo’s heaviest animal is Maggie, a giraffe, who comes in around 750 kilograms (about 1,653 pounds). Maggie lives with her sister, Molly, and was joined by another giraffe, Nuru, in March.

The zoo’s smallest animal is a leaf cutter ant, at about 5 milligrams. Zookeepers do not measure each ant individually, but use estimates based on the weight of an entire colony.

“We can tell a lot from an animal by its weight,” Ms. Ryan told a London radio station. The weigh-in can also measure how pregnant animals are doing, and can alert zookeepers to new pregnancies, which in turn helps with preparing for any births.

Zookeepers add the measurements and weights to the Zoological Information Management System, a database that is shared with other zoos around the world that includes information about threatened species. Conservationists in the wild can also use the information to determine the age of a particular endangered animal, for example.

Weighing animals can be challenging. Zookeepers use different ways to get them to step — or hop, skip or jump — onto the scale and stand up straight for measurements.

This year, for example, the zookeepers tricked Humboldt penguin chicks into walking over scales one by one by having them line up for their morning feed, the zoo said. It took the promise of tasty treats to get some Bolivian black-capped squirrel monkeys onto the scales.



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