Weighing and measuring 20,000 animals is no easy task. Just ask the zookeepers at the London Zoo in England, who recently conducted their annual animal checkup.
The zoo is home to a dizzying array of species—from 1,000 kilogram (2,200 pound) giraffes to tiny ants. Zookeepers use many tricks to ensure that the process goes smoothly. To weigh penguins, for example, keepers encourage them to hop onto a small scale by having their favorite food waiting as a treat on the other side.
“[The data] helps us ensure that every animal we look after is healthy, eating well, and growing at the rate it should,” says Mark Habben, a manager at the zoo.