London Zoo, which has more than 14,000 animals, held its annual weigh-in this week, an event that helps keep up-to-date records on their health and other data and measures the animals’ health.
While zookeepers measure animals throughout the year, every August they review all the information and invite news organizations to take a look.
“Having this data helps to ensure that every animal in our care is healthy, eating well, and growing at the rate they should,” said Angela Ryan, London Zoo’s head of zoological operations, in a statement. “We record the vital statistics of every animal in the zoo – from the tallest giraffe to the tiniest tadpole.”
The heaviest animal in the zoo is Maggie, a giraffe, who weighs about 750 kilograms (about 1,653 pounds). Maggie lives with her sister Molly, and was accompanied by another giraffe, Nuruin 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 Said to a London radio station. The weigh-in can also gauge how pregnant animals are doing, and can alert zookeepers to new pregnancies, which in turn helps prepare for any births.
Zookeepers add the measurements and weights to the Zoological Information Management System, a database shared with other zoos around the world that includes information about endangered species. Wildlife conservationists can also use the information to determine the age of a particular endangered animal, for example.
Weighing animals can be difficult. Zookeepers use a variety of methods to get them to step — or hop, skip or jump — onto the scale and stand up straight for the measurements.
This year, for example, zookeepers tricked Humboldt penguin chicks into walking the scales one at a time by making them line up for their morning meal, the zoo said. It took the promise of good food to get some Bolivian black-capped squirrel monkeys on the scales.