Venus Flytraps Can Count

The Venus flytrap's deadly embrace is not a simple reflex, but a clever calculation. To avoid wasting energy on false alarms like falling leaves or raindrops, the plant uses a form of botanical memory. When one of its tiny trigger hairs is touched, an electrical charge is generated but the trap remains open. If a second touch occurs within about 20 seconds, the accumulated charge crosses a threshold, causing the trap to snap shut in a fraction of a second. This two-step verification ensures the stimulus is likely a moving insect.

The plant's arithmetic continues even after the trap has closed. It needs to be certain it has captured a worthy meal before beginning the costly process of digestion. As the trapped insect struggles, it continues to stimulate the trigger hairs. Once the hairs have been touched around five times in total, the plant receives the final confirmation it needs. This signal triggers the digestive glands to secrete the enzymes that will break down the insect's soft tissues, allowing the plant to absorb vital nutrients unavailable in its native boggy soil.

This sophisticated counting mechanism, first studied in detail by Charles Darwin, is a remarkable example of adaptation. Without a brain or nervous system, the Venus flytrap uses a cascade of electrical and chemical signals to make a high-stakes decision. By counting touches, it perfectly balances the need to capture prey with the critical need to conserve energy, ensuring its iconic trap only deploys when a meal is almost guaranteed.