How do you get an emperor scorpion to hop up onto a scale to peer at its weight?

Or persuade a yawning Asiatic lioness to stand still for a minute so that you can take her measurements?

At the London Zoo, they do it very carefully — with patience, scales and bribes.

Mark Habben, the head of zoological management at the Zoological Society of London, said on Friday that 70 keepers had begun just such an undertaking the day before: the zoo’s annual weigh-in.

Armed with giant rulers, big (and little) scales, along with the animals’ favorite food, they are measuring, weighing and counting most of the 750 species in care of the zoo.