Crabs Attack Robot Rival After Perfect Mating Performance

In the animal world, attracting a mate often comes down to a show of skill. Birds sing. Deer fight. Some crabs wave.

For one species called the waving crab, this gesture is everything. Males raise and move their oversized claw to catch the eye of females.

Had to Stop the Test

Recently, scientists built a robot version of this crab to see what would happen if a mechanical rival entered the competition, writes Forskning.

The robot, named Wavy Dave, was designed to look and move like a real waving crab. These crabs live in tropical and subtropical areas, including southern Portugal.

That is where the experiment took place. The team wanted to see how real male crabs would react to Dave and whether they would adjust their waving to match his style.

From the start, Wavy Dave faced trouble. Some females seemed to notice something was strange about him. A few males became aggressive.

One even ripped off his claw. The researchers had to stop the test and repair the robot before continuing.

A Part of the Mating Ritual

Male waving crabs use their large claw as part of an important mating ritual. If a female accepts the invitation, she follows the male into his tunnel, where he fertilizes her eggs.

With so much at stake, competition is intense. Even though one crab tried to disable Dave, the robot still managed to take part in the contest for female attention.

This allowed scientists to watch how males reacted to a rival. They already knew that many animals adjust their courtship when other males are nearby.

But it is less understood how they respond if the rival changes its own behavior.

Wavy Dave could wave either slowly or quickly, and he could do so with a large or small claw. The findings were clear.

The real males matched his pace. When Dave waved slowly, they slowed down. When he waved quickly, they sped up.

The study was published in Proceedings of the Royal Society B: Biological Sciences.

It shows that in this muddy world of waving crabs, even an artificial outsider can set the rhythm of the mating game.