Montana Public Radio

Bug Bytes: Fiddler Crabs - The Kings Of Animal Weaponry

Jun 24, 2019

When you think of an animal with an impressive weapon, the first images that pop to mind might be a bull elk or moose with their massive antlers. Or maybe a bull elephant with its enormous tusks.

But the king of weaponry in the animal kingdom might surprise you: a fiddler crab that’s less than 2 inches long.

When it comes to battling over a mate, male fiddlers are equipped with one massive claw; a claw so big, it can weigh as much as the rest of the crab’s entire body.

While this massive and powerful appendage can come in handy during a battle, it’s most often used to flag down the ladies.

Males will wave their claw in the air as a form of courtship, with females choosing a mate based on claw size as well as the quality of the waving display. A more rigorous display suggests a male in his prime.

All that waving also serves as a way for males to size up their rivals, the smaller males quickly seeing who’s boss. While rare, equally matched males may need to thrown down, using their powerful weapons in battle.

But bigger is not always better. There’s a downside to a claw that big. It’s like trying to eat soup with a spoon the size of your body. Extraordinary, yes, but useless in feeding yourself. With only one functional claw to eat with, males need to work twice as hard as females to feed themselves.

Yes, the massive antlers, tusks, or horns of elk, moose, elephants and other species are indeed impressive. But the tiny male fiddler crab, with its single, massive claw, reigns supreme in the world of extreme animal weapons.

Bug Bytes is made possible by the Missoula Butterfly House and Insectarium, and Montana Public Radio. This show is also supported by funding from the Greater Montana Foundation: Encouraging communication on issues, trends and values of importance to Montanans.