LONDON, UK (CNN) -- The London Zoo is in the middle of a major exercise, a weigh-in.
All of the animals, big and small, are weighing in at the London Zoo. The owls are easy, the tigers are tricky, and the camels took a month to train. Zookeeper Angela Ryan says, "Every day we've kinda gone through this routine of trying to walk them on the scale. We've used kind of positive reinforcement and we've used one of his favorite foods - there is like this pellet that he really loves. So we've had to eventually used that to get him to go on. But now he's comfortable and he's confident and we've got a weight today."
This isn't all about showing off. Every year these measurements are entered into a global database so that zoos around the world can compare how their own animals are doing.
And for some of the birds, a little extra weight means the difference between flying and staying grounded. Zookeeper Darren Jordan says, "We know when it is at that weight they will perform okay during flight. If they get a little too heavy they stop behaving. They get fat and they go no I'm not going to do that. So you have to keep their weight at a perfect level."
Even the giant snails cannot escape the scales of the London Zoo. And thanks to a new program, one of the heaviest animals, the camels, have actually lost a few pounds this year.