Poster Girl of Tropical Summer: Land Crabs

Tara A. Spears

“There she was just a walkin’ down the street… clicking her pinchers, singing do wah diddy…”

When it comes to cool and unusual creatures, the tropics excel in bizarre species. My favorite is the Mouthless Land Crab / Cangrejo Azul, which is typically active at night unless it’s the migration period after the rains start. To me, no matter what the weatherman says, it’s not the official rainy season until I see the crabs. C. crassum is generally shy, preferring to burrow in the jungle, but during the migration you can see them journeying any time of day on their way to and from the ocean to reproduce. I’ve had crabs resting in the dog’s water dish, in an outdoor fountain, and one year even joining me in the shower! The hotels and houses of Jaltemba Bay sit between the land crab’s habitat and the ocean, so expect to see them when the rains first start. Please don’t kill them — relocate any crabs to where they can continue their journey.

Look at that face! It’s a combination of Star Wars chic and exotic beauty. The Mouthless Land Crab is easy to identify: it’s a mid- to large-sized crab characterized by an oval, thick, inflated shell that is wider than it is deep, and one claw (chelae) that is larger than the other. They have a wide forehead with eyes on stalks set near the sides of the body. Mouthless crabs have a purplish-blue shell, red legs and whitish pincers. The males are brighter in color than the females, who normally outnumber males by a ratio of three to two.

The Mouthless Land Crab resides in coastal environments that may include brackish water, estuaries, and mangroves within freshwater river basins adjacent to salt marshes, as they require access to the sea for breeding and larval development. They live in burrows with multiple entrances that they dig in dry mud among plant roots, including mangroves, and are also found around rocky crevices.

According to Crab.org, what’s ecologically beneficial about the C. crassum crab is that it’s a jungle garbage disposal. Not only is this crab cannibalistic, feeding on insects and carrion, but it also eats leaves and fruit. Young individuals are often very colorful, leading to a level of popularity in the pet trade, but as land crabs grow older their colors tend to fade. At all ages, males are brighter than females. In the wild, C. crassum crabs are also an important food source for alligators, birds and raccoons.

It’s good to know that Mouthless Land Crabs are maintaining their numbers and are considered of Least Concern on the extinction list. But there is still pressure on this species, as they are an important food source in southern Mexico. The crabs are caught by hand and sold fresh in local markets. Land crabs are also subject to a high level of illegal commercial exploitation for the pet trade due to their attractive colors. Lastly, the land crab is losing habitat due to coastal building throughout Mexico.

If you encounter one of these exotic creatures on your morning walk, don’t expect a warm welcome. The crab immediately freezes and takes a defensive posture with its claws up, ready to battle. Spunky little creatures! Snap a picture and let them continue their journey.