https://www.cnet.com/news/bees-know-nothing-and-thats-a-good-thing-new-study-says/

Most of us -- scientists included -- thought only humans and other animals with big brains could grasp the concept of zero. A new study, however, suggests honey bees also get the idea, making them cleverer than we may have thought. The results may also influence future designs for artificial intelligence.

"Zero is a difficult concept to understand and a mathematical skill that doesn't come easily — it takes children a few years to learn," Adrian Dyer, a co-author of the new study and a researcher at RMIT University in Melbourne, Australia, said in a statement. "We've long believed only humans had the intelligence to get the concept, but recent research has shown monkeys and birds have the brains for it as well. What we haven't known -- until now -- is whether insects can also understand zero."