A new study from Tel Aviv University (TAU) proves an acoustic interaction between plants and insects. The researchers found that female months decide where to lay their eggs based on ultrasonic sounds emitted by nearby plants.

When plants emitted distress sounds, the female moths chose healthy plants that were not emitting such sounds. These sounds are ultrasonic, beyond the hearing range of the human ear, but they are audible to the moths.

The study was conducted in the laboratories of Professor Yossi Yovel of the School of Zoology and Professor Lilach Hadany of the School of Plant Sciences and Food Security at TAU’s George S. Wise Faculty of Life Sciences. It was led by students Dr. Rya Seltzer and Guy Zer Eshel in collaboration with scientists from the Plant Protection Institute at the Volcani Institute. The paper was published as a pre-print on December 27, 2024, in the journal eLife.

This study follows a dramatic discovery published by the same researchers about two years ago, which generated worldwide interest. Plants under stress emit sounds at ultrasonic frequencies, above the range of human hearing, but detectable by many animals. That discovery opened the door to extensive research on acoustic communication between plants and animals.

“After proving in the previous study that plants produce sounds, we hypothesized that animals capable of hearing these high-frequency sounds may respond to them and make decisions accordingly,” Professor Yovel says. “Specifically, we know that many insects, which have diverse interactions with the plant world, can perceive plant sounds. We wanted to investigate whether such insects actually detect and respond to these sounds.”

“We chose to focus on female moths, which typically lay their eggs on plants so that the larvae can feed on them once hatched,” Professor Hadany adds. “We assumed the females seek an optimal site to lay their eggs, a healthy plant that can properly nourish the larvae.

“When the plant signals that it is dehydrated and under stress, would the moths heed the warning and avoid laying eggs on it? To explore this question, we conducted several experiments.”

The first experiment aimed to isolate the auditory component from other plant features like color and scent. The researchers presented the female moths with two boxes: one contained a speaker playing recordings of tomato plants in a state of dehydration, while the other box was silent. The moths showed a clear preference for the “noisy” box, which they likely interpreted as a living plant, even if the plant was under stress. The researchers concluded that the moths do indeed perceive and respond to a playback of plant-emitted sounds. When the researchers neutralized the moths’ hearing organs, this preference disappeared and they chose both boxes equally, clear evidence that the preference was specifically based on listening to sounds, and not on other stimuli.

In the second experiment, the female moths were presented with two healthy tomato plants: one with a speaker playing sounds of a drying plant, and one that was silent. Again, they showed a clear preference, but this time for the silent plant, from which no distress sounds were heard and probably serving as a better site for laying eggs.

In a final experiment, the moths again faced two boxes: one silent and the other containing male moths, which also emit ultrasonic sounds at a frequency similar to plant sounds. This time, the females showed no preference and laid their eggs equally on both boxes. The researchers concluded that when deciding where to lay their eggs, the females specifically respond to plant-emitted sounds and not to the sounds made by males.

“In this study, we revealed the first evidence for acoustic interaction between a plant and an insect,” the researchers conclude. “We are convinced, however, that this is just the beginning. Acoustic interaction between plants and animals doubtlessly has many more forms and a wide range of roles. This is a vast, unexplored field, an entire world waiting to be discovered.”