London Zoo lured lions, penguins and other animals on to scales and measuring frames on Thursday at the launch of an annual weigh-in of 20,000 captive creatures in some 700 species.
The annual weigh-in allows zookeepers to record the animals' weight and height and send the data to a global information system, the Zoological Society of London (ZSL) said.
"With different personalities and temperaments to take into account, zookeepers used ingenious tactics to entice the animals to stand up and be measured," it said.
The tactics included enticing hungry penguins to walk over scales as they lined up for their breakfast, and hanging the lions' morning feed high up to encourage them to stretch to their full height.
"We have to know the vital statistics of every animal at the zoo - however big or small," said Mark Habben, the zoo's manager.
"It helps us to ensure that every animal we look after is healthy, eating well, and growing at the rate it should - weight is a particularly important indicator of health, and we can even detect pregnancies through a growing waistline," Habben said.
"By sharing information with other zoos and conservationists worldwide, we can all use this knowledge to better care for the endangered species we're striving to protect," he said.