Zoology: P-p-p pick up a penguin to see if it's p-p-p put on weight

I would love to weigh a penguin. I wouldn't mind assessing a stoat, either, or taking the inside leg measurements of a baby giraffe. A tarantula spider, however – well, not so much. At London Zoo this week, however, it isn't just the warm-eyed, cuddly creatures that will be given a once-over as part of the annual "weigh-in".

Some 16,000 creatures from 750 species will be coaxed from their slumbers and cajoled onto the scales and against measuring posts, like some giant animal version of a WeightWatchers meeting. The difference: it doesn't matter if the parakeets or meerkats have put on an ounce or two. In fact, it might possibly be a good thing, according to Adrian Walls, the head of the bird section at the Zoo.

"We weigh because it is a very good indication of an animal's long-term health and because each animal has a unique number with ZIMS (the international Zoological Information Management System)," he says. "We do this each year so we can spot trends or problems in an animal's long-term well-being. It's like updating a health passport."

Not only does this allow them to track the health of animals in the zoo in London but also the long term-health of that species. All very worthy and serious work – but I confess I would still just want to weigh a penguin for the Lolz. In fact, says Walls, the penguins are the least Lol-worthy when it comes to weighing.

"You try to coax them onto the scales and they just want to jump in the pool – you have to follow them in sometimes."

What I really want, he says, are the hornbills: "You give them one command and they weigh themselves." Takes the labour out of things, I'm sure, but where's the fun in that?