From humans to cockatoos, many species love to show off their dance moves, usually as a means of attracting a mate or prewarning the competition to back off. Mangrove crabs (Perisesarma eumolpe), colorful little crustaceans from Southeast Asia, take this boogying to a whole new level.
After defeating their love rivals, the males of the species perform an elaborate “victory dance". The dance involves placing one claw downwards while shaking the other one up and down. This signal is seen by the defeated Romeo but might also create some acoustic vibrations to intensify the warning.
Scientists have known about mangrove crabs and their seemingly cocky behavior for decades. However, there are very few scientific studies on the animals performing post-fight triumph displays and it remained unclear why they perform it. After all, if your competition is already defeated, surely this celebratory gloating is a waste of precious energy?
A recent study published in the journal Ethology explains that this behavior is probably to “lessen the probability of a future contest… by preventing unnecessary escalation.” Risking both life and limb in a courtship fight can be very costly to an animal. That’s why many animals engage in courtship rituals before any physical altercation comes in. For these crabs, their post-fight wiggling is to reduce the chances of a re-match.
Basically, it tells the other crab: “you want some more of this, huh?”
Biologists from the National University of Singapore came to the discovery by observing 77 fights between randomly paired male mangrove crabs and giving them an aggression score from 0 to 3. Just over half the tussles resulted in the winner performing a victory dance. In these cases, the defeated crabs were significantly less likely to re-challenge them into a fight.
The researchers note that there are anecdotal reports of other species performing a victory dance, including species of amphibians and birds, yet this is one of the few studies to have specifically examined the behavior.
Crabs might not look too pretty but they are masters of seduction, equipped with all kinds of weird and wonderful courtship rituals. Another study last year found that males from one species of fiddler crab quickly jitter their claws when an interested female approaches the entrance to their burrow. Waving like this produces vibrations and pulses that entice the female to come down into the burrow.
6
