Number sense in animals is like understanding how many things there are without counting. Just like how you know how many fingers you have without counting, animals have a sense of how many things are around them, too.
Some animals, like bees and birds, are really good at counting. Bees can count up to four and birds can count up to around eight. They use this ability to keep track of their food and their babies.
Other animals, like chickens and dogs, have a number sense but not as good as those of bees and birds. They can tell the difference between small numbers and big numbers, but they can't count very well.
Scientists have studied animals to learn more about their number sense. They have found that some animals use their number sense to find food or to know if another animal is nearby. For example, if a group of monkeys is eating fruit and one monkey takes more than its fair share, the other monkeys can tell that something is wrong and will react accordingly.
Overall, just like humans, animals have a sense of how many things are around them, which helps them survive and navigate their environment.