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The Verge Review of Animals: the Halloween Crab

The Verge Review of Animals: the Halloween Crab


Where we're going, we don't need costumes

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This column is part of a series where Verge staffers post highly subjective reviews of animals. Up until now, we've written about animals without telling you whether they suck or rule. We are now rectifying this oversight.

Either we were jet-lagged or just adrenalized by the always-awake ocean yards from our bungalow, but by 5 AM on our first full day in Nosara, Costa Rica, we were up and walking to the beach.

Our walk came to a halt when we hit a small gateway of vegetation, the kind of dense-trees-before-you scene you might find in a horror movie. It wasn’t the brush that stopped us though; it was the sound, a distinct, rapid, tit-tit-tit-tit-tit noise, surrounding us. A group of researchers from the Smithsonian Tropical Research Institute once described it as "similar to that produced by rapidly running an object over the teeth of a stiff comb;" New Yorkers might liken it to "I turned on the light and a dozen cockroaches skittered out of sight."

Land crabs in little technicolor dreamcoats
Only later, once I was able to connect to Wi-Fi, did I learn that we had just had our first encounter with Gecarcinus quadratus de Saussure, otherwise known as the Halloween crab. And only later, in the light of day, did I see how awesome they are.

Halloween crabs are nicknamed so because of their brilliant colors — they have a tar-black carapace, blood-orange legs and purple claws, with a pair of yellow spots behind the eyes. They are land crabs in little technicolor dreamcoats. They measure around 2 inches across the carapace and 4 inches from claw to claw, but they have an adorable way of making themselves bigger when you near them, putting up their claws as if to say "It wasn’t me!" while they scuttle away.

Despite the fact that they were first described and named in 1853, there isn’t a whole lot of information readily available online about these crabs. What we do know is this: they’re found in neotropical coastal rain forests, along the west coast of Central America from Mexico to Ecuador. They’re burrowers, living on land, and they’re nocturnally active, which explains why we saw so many of them just before daybreak.

But even though they’re well-adjusted terrestrial crabs, they still live close enough to the water to migrate there for reproduction. During the long dry season of November to April, they’ll go underground, and then re-emerge on the first rainfall, signaling the start of the green season. For Halloween crabs, spring break is a wet one.

Thousands of Halloween crabs will appear on the beach to spawn, which one PhD student
studying the crab described as "a big pulse of biomass into the ocean all at one time." Hatched larvae go through successive development stages in or near the water, then move to land as juvenile crabs, where they will spend most their adult lives (which can be up to 10 years long).

Unlike ocean crabs, which eat various fish parts and algae, the Halloween crab is described as
largely herbivorous, eating leaf litter and other plant-based foods. There’s even some suggestion that these crabs' leaf-eating and burrowing habits may be good for the soil around them, that they may "facilitate, over months or years, the movement of nutrients to deeper soils where roots may subsequently forage," writes Peter Sherman, a systems ecologist who studies tropical lowland rainforests.

But of course, you might be wondering if this exotic coastal rain forest crab is poisonous, as some brightly colored species are. The consensus is that they’re generally harmless. Their benignness is all the more remarkable when you consider all of the other species in the region that are not — the venomous snakes, hungry crocodiles, creepy arachnids, stinging scorpions, and poison-dart frogs. After a couple days in Nosara, I was happy to wake up in the morning and find only a Halloween crab waiting for me in the sneakers I left outside.

The Halloween Crab

Verge Score: 10.31


Verge Score

Good Stuff

  • Purple claws

  • Herbivorous

  • Benign

Bad Stuff

  • High creep-out potential

  • Anti-social for six months of the year