If you own a Venus flytrap, don’t embarrass yourself by counting on your fingers in front of it. According to a new study, these carnivorous plants are able to count the footsteps of their prey to make sure they’re real insects and figure out how big they are … and they don’t need fingers to do it.
Researcher Rainer Hedrich of the University of Würzburg in Germany reports in the latest edition of Current Biology that the magic number for a Venus flytrap (Dionaea muscipula) is “five.” That’s how high it needs to count to a) make sure it’s not being tricked by a piece of fuzz or a raindrop and b) determine how much digestive juices it needs to make to eat what it caught.
That’s right … the Venus flytrap counts how many times something touches or steps on the sensory hairs inside the trap leaves. Using crickets, Hedrich and his team patiently fed flytraps and watched what happened as the bug first landed in the trap and then began to walk and wiggle around.
Here’s what they saw. One touch put the Venus flytrap on alert. Two touches meant there might be something trying to sneak away so it shuts its trap around it. At that point, the plant produces a hormone called jasmonic acid that gets its system primed for eating. At the third and fourth footsteps, it starts making digestive enzymes. Step five triggers the plant to begin pumping them into the trap to break down the insect and allow it to absorb it. If a big cricket continued to kick, the plant upped the amount of digestive enzymes proportionately. Hedrich said the average number of kicks until death was 63.
Venus flytrap digestion takes a lot longer than a post-Thanksgiving dinner football game. The researchers observed them keeping their traps tightly shut for up to a week or more before opening up for another course of crickets.
Is this real math? Well, the flytrap seems to keep track of the number of footsteps and it eventually subtracts the bug from its trap, giving the plant nutrients to divide among its branches and multiply its leaves. It’s not calculus but it’s more than most of us can remember from grade school math class.