Zoo keepers across the country have been busy, counting up all the creatures in their care. Newsround's Sonali went to London Zoo to find out more about how it's done...
As you can imagine, it's a huge job - and a tricky one - as most of the animals won't keep still! Can YOU count how many flamingos there are in this picture?
And some of the creatures won't even stay on the ground... Here's Sonali trying to keep track of the butterflies flying around! It looks like she's concentrating hard.
But not all the animals are that difficult, taking stock of the monkeys looks slightly easier!
And have you ever wondered how to count penguins? Well, Sonali found out how it was done, and even met a few of the cute creatures.
What's scared Sonali? Perhaps the penguins aren't all as friendly as they seem...
But they're certainly very curious creatures. Perhaps they were wondering what all the fuss was about?
And there was a BIG fuss. Sonali wasn't the only reporter at the zoo that day, there were LOADS of photographers keen to get a glimpse of the animals.
And they weren't the only ones wondering what was going on! By law, the count has to happen every year, so zoo keepers monitor breeding and make sure none have gone walkabout.