It is a basic ability for humans to tell more from less Surprisingly, a number of animals1this ability too. They will2more of something. Horses, for example, will go for a group of three apples instead of two apples.
This ability is3to animals in lots of ways. It helps them4the larger group of friends. Many fishes, for example, join groups for 5. If a predator (掠食动物) comes, a fish in a group of 40 is less possible to become lunch than a fish in a group of 10. So if a fish has a choice between two groups, it's safer to join the6one. A sense of number even helps keep the7. For example, a monkey group will avoid fights with other groups when they find their8 is not an advantage.
Also, the ability to do simple9is a sure thing for some animals. They10the difference between one, two, and three.
Some others can count much higher than three.
