Sally Lightfoot crab

The Sally Lightfoot crab, also called the red rock crab, is one of the most common crabs on the Pacific coast of the Americas. It has a flat, round shell a little longer than 8 centimetres, five pairs of legs and two small blocky claws. Young crabs are dark, but adults can be bright red-orange, mottled brown, pink or yellow.

This crab lives on rocks right at the edge of the sea, just above the reach of the waves' spray, in places with strong, turbulent surf. It lives along the Pacific coast of Mexico, Central America and northern South America, on islands such as the Galapagos, and also along the Atlantic coast of South America. It eats mostly algae.

Quick on its feet

Sally Lightfoot crabs walk on the tips of their broad, flat legs and move very quickly. They are agile enough to leap from rock to rock, which makes them hard to catch. Young crabs are black or dark brown, which hides them on black lava rock, but adults often turn red or orange. Charles Darwin collected this crab during the voyage of HMS Beagle, and the writer John Steinbeck described its shiny colours.

A varied diet

Algae are the main food, but the crab also eats other plants, sponges, clams, other crustaceans, fish, bird eggs and droppings, dead animals and sometimes young sea turtles. When food is scarce it can even eat other crabs. On the Galapagos, crabs have been seen picking ticks off marine iguanas, a kind of cleaning partnership. The octopus and the chain moray eel hunt this crab. Fishermen use it as bait.

On the globe

The globe shows the crab on the rocky shores of the Galapagos and other Pacific and Atlantic coasts. Look for the red-orange shell on dark rock.