Carnivorous plants like the Venus flytrap cope with poor soil by eating bugs. But the cost of insect hunting is high. Catching prey requires Dionaea muscipula to snap down quickly and then carry out the energy-intensive process of digestion. To balance the costs and benefits of eating meat, the plants have developed a counting system to identify real prey from false alarms, according to a new study. To understand how the flytrap distinguishes a potential food source from a false alarm like a raindrop, researchers observed the electrical and chemical response of the plant to touch stimulation. In order to mimic insect prey, the scientists stimulated the hairlike sensors located on the plant’s trap. Touching the sensors two times quickly caused the leaf trap to snap shut. The researchers continued stimulating the sensors in order to mimic a struggling insect trying to break free. At this stage, the plant produced a plant defense hormone, jasmonic acid—the same one released in noncarnivorous plants when being eaten by an insect. In the Venus flytrap, this hormone triggers the production of digestive enzymes. After a fifth touch, the plant produced chemicals used in absorbing nutrients, the team reports online today in Current Biology. So thanks to a bit of counting, the Venus flytrap can save its energy for when it’s really needed.

(Video credit: Science/Böhm and Scherzer et al.)