In a greenhouse in Tel Aviv, a moth is faced with a choice. On one side: a fresh, well-hydrated tomato plant. On the other, a plant that’s slightly begun to dry out. To human eyes, the two look similar. But the moth hears something we cannot—ultrasonic clicks, like tiny popcorn pops, coming from the thirsty plant. She turns away.

In a study that opens a new window into the invisible world of plant-insect interactions, scientists at Tel Aviv University have found that female moths can hear and respond to sounds emitted by stressed plants. These sounds—inaudible to humans but within the range of moth hearing—may guide the moths in deciding where to lay their eggs.

“This is the first demonstration ever of an animal responding to sounds produced by a plant,” Yossi Yovel, a professor of zoology at Tel Aviv University, told the BBC.

Published in the journal eLife, the study reveals that female Egyptian cotton leafworm moths (Spodoptera littoralis) are more likely to avoid laying eggs on plants emitting distress sounds (clicks triggered by dehydration) than on silent, healthier ones. However, they may also be drawn to those very sounds when other cues are missing.

What Plants Are Saying—And Who’s Listening

Plants have no vocal cords or ears. But under stress, such as during drought, they emit ultrasonic pops, likely produced by air bubbles collapsing inside their xylem, the tissue that carries water. The phenomenon, known as cavitation, had long been suspected to generate vibrations. In 2023, researchers at the same university confirmed that these vibrations could be airborne and detectable from meters away by animals with ultrasonic hearing, like moths and bats.

The team wondered: could moths actually use these sounds to make reproductive decisions?

They focused on female moths, whose choice of egg-laying site can determine the survival of their larvae. A healthy host plant offers food and shelter. A drought-stressed one might doom the offspring.

So the researchers designed a series of experiments. In one setup, moths were placed between two tomato plants: one freshly watered, the other left to dry out for three days. The moths overwhelmingly laid their eggs on the well-watered plant.

But the real surprise came next.

When no physical plant was present, and only a speaker emitted the ultrasonic clicks of a drying tomato plant, the moths moved toward the sound. They laid eggs near the speaker more often than near a silent control.

This contradiction puzzled the researchers until they considered how moths use multiple senses. In the absence of other cues, the clicking sounds might simply signal the presence of any plant. But when actual plants are present, the moths seem to interpret those same sounds as warnings.

“The females’ oviposition preference was reversed to the side without the acoustic signal,” the authors write. “This might suggest that the acoustic signal interpretation is content dependent.”

When Silence is Quite Revealing

In another experiment, the team placed two healthy plants in the arena, adding ultrasonic playback to one. The moths preferred the silent plant, suggesting they used the sound to avoid a potentially compromised host.

To test whether sound alone was guiding them, the team deafened some moths by carefully puncturing their tympanic membranes. These moths showed no preference in where they laid their eggs. That result confirmed what the researchers suspected: the decision was based on hearing.

They also tested whether the sound had to come from a plant. Male moths emit their own ultrasonic clicks during courtship, with a similar frequency to the plant distress sounds. Yet female moths laid eggs evenly when placed between clicking males and a silent control. The response was specific to plant sounds.

“Plants could evolve to make more sounds or louder ones if they were of benefit,” said Lilach Hadany, a professor of evolutionary biology at Tel Aviv University. “And the hearing of animals may evolve accordingly.”

A Hidden World of Plant-Animal Acoustics

While this study focuses on one moth species, the findings hint at a much larger, little-understood world. Many insects and mammals can hear ultrasonic frequencies. If they too respond to plant sounds, it could mean plants and animals have been engaged in acoustic eavesdropping—or even coevolution—without us ever realizing it.

Still, the researchers are cautious. The sounds emitted by plants are likely a byproduct of physical stress, not evolved signals. In scientific terms, they’re “cues,” not “communications.”

“[This interaction] cannot be considered ‘communication’ according to the conservative definition of the term, which relies on signals that have evolved to convey a specific message,” the authors write.

The implications ripple outward. Farmers could one day use ultrasonic sensors to detect crop stress early. Ecologists might rethink how animals navigate plant-rich environments. And evolutionary biologists may need to add “sound” to the list of senses linking plants and animals.

“This is a vast, unexplored field,” said Hadany. “An entire world waiting to be discovered.”