Animals Mini caterpillar vibrates in defense of its mini territory
A tiny butterfly caterpillar defends its territory - the tip of a birch leaf - with no less commitment than large predators do. This was reported by a Canadian research team in the "Journal of Experimental Biology".
12.04.2025, 04:44
SDA
The caterpillar beats loudly against the foliage, scratches and vibrates indignantly, as the team explains in the journal. The North American moth Falcaria bilineata lays its eggs on the twigs and leaves of birch trees. When the caterpillars, which are only half a millimeter to two millimeters long, hatch, they crawl onto the tips of nearby leaves.
In the past, it has been observed that the minis regularly vibrate there - it was assumed that this was to scare off rivals. The minis cannot see very well, as explained.
Insect tiny with a claim to ownership
Researchers led by Jayne Yack from Carleton University in the Canadian capital Ottawa have now tested in the laboratory whether this is actually territorial behavior. They placed another caterpillar of the species in a territory 18 times and observed what happened. And that was quite a lot: the original inhabitant of the leaf tip made noise by drumming against the leaf, wriggling, scratching and vibrating at a frequency of 25 movements per minute. There was no biting or shoving amidst all the commotion.
The researchers report that the noise usually made a sufficient impression: The raging caterpillars kept their territory in around 70 percent of the test runs with a clear winner - that was 10 out of 14. In four cases, neither of the two caterpillars was still on the leaf tip at the end of the time taken into account.
And what if the newcomer did win the battle for the leaf tip? As soon as there was physical contact, the original inhabitant often made a daring escape and jumped off the leaf on a silk thread, the researchers explain. Two caterpillars never ended up sharing a territory.
Other examples probably overlooked
The tiny moth caterpillar is therefore one of the smallest animals in which territory defense has ever been observed. Large animals can have territories of hundreds of square kilometers in size - which are defended against rivals with all kinds of markings or roaring, but also with excessive physical violence.
According to the biologists working with Yack, there are probably no similar case reports on the territorial defense of small insects for a very specific reason: the event has simply been overlooked. Further analyses will show whether the moth caterpillars' behavior mimics the gait pattern of typical predators such as spiders.
DOI: 10.1242/jeb.249796
