Meet the Sally Lightfoot Crabs of the Galapagos Islands

While not endemic to the Galapagos Islands, the Sally Lightfoot Crabs are one of the most striking species for wildlife lovers to encounter on the archipelago, notable for their vibrant red and blue colouring and lightning-fast agility. Found in abundance around the coastal rocks and sandy beaches, they play a vital role in maintaining the delicate balance of the islands' eco-system. 

Encounter the Sally Lightfoot Crabs on a Galapagos Cruise

A well-organised, small-group Galapagos cruise is one of the very best ways of seeing a wide range of land and marine wildlife. Exploring the beaches of both the large and small islands will provide many opportunities to catch sight (albeit often fleeting) of the brightly coloured Grapsus grapsus, otherwise known as the Sally Lightfoot Crab.

Agile By Name and Nature 

One of the more intriguing theories as to how the crab got its name is that it's due to its amazing agility, as it has the ability to jump from rock to rock, scale vertical slopes and run in all four directions without missing a step. It's said the name comes from a comparison to a particular Caribbean dancer with similar abilities!

Physical Appearance

As youngsters, the crabs sport small red spots and are darker in appearance, which provides them with the maximum degree of camouflage in their volcanic, rocky coastal habitat. As they mature, they moult their shells several times, and their spots enlarge each time until they reach adulthood. Adults' distinctive colouring ranges between shades of yellow, pink, red-brown and bright red and blue – depending on their habitat.

In maturity, the shell (or carapace) measures around 8 to 12 centimetres in diameter. Like other crab species, they have five sets of legs: four wide, flat pairs and one set of front pincers.

Behaviour

Once mature, the crabs are solitary unless mating, preferring to spend the majority of their time tucked away in the rocks. They usually come out to do the majority of their feeding at low tide in the shallowsin large groups, however.When feeding or hiding in rocks they're able to withstand pounding waves by flattening their bodies and gripping on with their legs. If threatened they have the ability to spray water and even shed a leg in order to defend themselves.

Breeding and Birthing

The mating process is unique: females have multiple partners throughout the breeding season. The male deposits sperm in the female's spermatheca, and the female then releases the fertilised eggs. But what's unusual is that the remainder of the sperm is stored in the spermatheca. The female does not mate again until all the reserves of sperm have been used.

The female carries the fertilised eggs in the lower part of her stomach until they are ready to hatch. After hatching, the larvae head out to the deeper waters of the ocean to feed on plankton. They remain there until they evolve into juvenile crabs and return to shore, where they begin to feed on not just their staple diet of red and green algae, but also any other scavenged and foraged food found on the beaches – including dead fish, mussels, and bat and bird droppings.

Distribution

Also known as the Red Rock Crab, the Sally Lightfoot Crab is one of the most populous crab species in the Galapagos Islands and along the western coastline of South America. It is also found on the Atlantic coast of Africa.

Encounter the Sally Lightfoot Crab on a Galapagos Cruise

A Galapagos cruise is the ideal way to make the most of the famously unique wildlife, providing many opportunities to come ashore and encounter the Sally Lightfoot Crabs in delightful flashes of red and blue as they scurry across the rocks and beaches of the islands.