Scientists Find First Evidence of Auditory Interaction Between Animals and Plants: Study

Plants can do amazing things, from converting carbon dioxide into food and oxygen, to communicating with other plants, fungi and even animals.

In the first study of its kind, scientists from Tel Aviv University (TAU) have documented an acoustic interaction between insects and plants. The ultrasonic distress sounds emitted by plants were detected by female moths who used them to decide where to lay their eggs.

“Insects rely on plants’ visual, chemical, tactile, and electrical cues when making various decisions. Recently it has been found that plants emit ultrasonic sounds, which are in the hearing range of many moths, especially under dehydration stress,” the authors of the study wrote. “We reveal evidence for a first acoustic interaction between moths and plants, but as plants emit various sounds, our findings hint to the existence of more currently unknown insect-plant acoustic interactions.”

The researchers discovered that female moths prefer plants that are healthy and not emitting stress sounds. The ultrasonic sounds they give off are beyond the range of what the human ear can detect, but moths are able to hear them.

The research was conducted in laboratories run by Professor Lilach Hadany from TAU’s School of Plant Sciences and Food Security and Professor Yossi Yovel from the School of Zoology.

The study followed another discovery published by the research team about two years earlier — that plants under stress emit ultrasonic sounds that are detectable by many animals at frequencies above the range of what humans can hear.

“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. 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,” Yovel explained in a press release from TAU.

Hadany said the new study focused on female moths, since the researchers assumed they would look for a healthy, nourishing plant as the place to lay their eggs, given that larvae feed once they hatch.

“Thus, 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,” Hadany said.

In their first experiment, the research team aimed to isolate the auditory features of plants from other components like scent and color. They presented the moths with two boxes: one silent and one containing a speaker playing recorded sounds of dehydrated tomato plants.

The moths clearly preferred the “noisy” box, which demonstrated they had heard and responded to the playback of plant-emitted sounds. When the moths’ hearing organs were neutralized, they stopped preferring either box and chose both equally.

In a second experiment, the team presented the female moths with a pair of healthy tomato plants. Again, one was silent, and the other had a speaker playing drying plant sounds. The moths again demonstrated a clear preference, but for the silent plant this time, which likely served as a better place to lay their eggs.

Another experiment involved the moths again facing two boxes: one containing male moths — who emit ultrasonic sounds of a frequency that is similar to plant sounds — and the other silent. The females demonstrated no preference, laying their eggs on both boxes equally.

The researchers concluded that female moths respond specifically to sounds emitted by plants when choosing where to lay eggs, and not to other sounds, such as those made by male moths.

“In this study, we revealed the first evidence for acoustic interaction between a plant and an insect. 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,” the researchers concluded.

The findings of the study, “Female Moths Incorporate Plant Acoustic Emissions into Their Oviposition Decision-Making Process,” were published in the journal eLife.