How the Venus Flytrap Counts

The Venus flytrap is one of the few plants that catch and digest animals. In the wild, it grows only in a small area of wetlands in North and South Carolina, in the United States. The soil there contains very little nitrogen, an important nutrient for plants. By catching insects, the flytrap obtains the nitrogen that its roots cannot find.

Each trap consists of two leaf-like parts that can close quickly, like a pair of jaws. On the inner surface are several tiny trigger hairs. If an insect touches one of the hairs only once, nothing happens. The trap closes only if the hairs are touched twice within about thirty seconds. This system helps the plant avoid wasting energy on false alarms, such as a falling raindrop.

In 2016, a team of scientists in Germany discovered that the plant keeps counting after the trap has closed. As the trapped insect struggles, it touches the hairs again and again. After about five touches, the plant begins to produce chemicals that break down the insect's body. In this way, the flytrap spends energy on digestion only when it has caught something that is actually moving.