Shoreline Creatures of the Galapagos

Sally Lightfoot crab

Saltwater crabs pervade almost every shore you visit, but in the Galapagos Islands – which are known for their unique biota – there is only one species that really stands out from the rest. Sally Lightfoot crabs in Galapagos are popular among tourists due to their remarkably bright colors and agility. This magnificent creature is able to dance through the deep black lava rocks and withstand the crashing waves of the Pacific.

Sally Lightfoot Crab in Galapagos

Scientific Specifications

Family: Grapsidae
Genus: Grapsus
Species: G.grapsus
Binomial name: Grapsus Grapsus

Actually, this crab is rumored to have been named after a Caribbean dancer due to its agility and its lightfoot way of dancing! The Sally Lightfoot crab has ten legs that allow it to run in four different directions. Additionally, their spectacular reflexes and speed make it seem as if they could predict the mind of their predator. This feature also makes them next to impossible to catch! As writer John Steinbeck once commented in The Log of the Sea of Cortez that, when it comes to catching the crab, “[man’s] tendency eventually is to scream curses, to hurl himself at them, and to come up foaming with rage, bruises all over his chest.”

How do Sally Lightfoot Crabs in Galapagos Survive?

However, speed is extremely important for their survival. The Sally Lightfoot crab has a wide range of predators that includes octopuses, fishes, lava herons, moray eels, lava lizards, and even introduced rats, cats and dogs, thus it has to be extremely agile in order to survive. This is also the reason they spend 2/3 of the day hiding in cracks amongst the rocks.

Sally Lightfoot crab holding on to a rock
Sally Lightfoot crab sunbathing
Sally Lightfoot crabs eating scraps

What do Sally Lightfoot Crabs eat?

Nevertheless, these colorful crabs are opportunistic predators, meaning that they will eat almost anything they come across including barnacles, young sea turtles, other crabs, and young birds, as well as dead fish, broken eggs, and even bird droppings and sea lion placenta. Their claws become very useful for this varied diet, like powerful and sharp spoons, they use them to rip apart the meal and spoon out the goods. This role as beach predators, grazers and scavengers make them critical to a healthy beach ecosystem.

What adaptations have they developed?

In addition to their speed, these agile crabs have a few tricks to escape the claws of hungry hunters. First, we must take into consideration that the Sally Lightfoot crab has a very tough shell to protect its fleshy body. This shell tends to become stronger over time. However, this also means that their shell is significantly tender when they are young, but there’s nothing to worry about as their first shells are dark brown or black so they can blend in with the rocks and hide from their predators.

On the other hand, if the crab feels severely threatened it is able to detach one of its legs (which it can regenerate) or spray water as a defense mechanism to shock the predator. However, the primary purpose of holding water in their shell is to allow them to breathe during their time on land. As they spend a large amount of time outside of the water, they are able to pour liquid over their gills every once in a while to keep breathing.

Considering that the Sally Lightfoot crab has so many predators, one would think that blending in is one of their top priorities. But they don’t. Most Sally Lightfoot crabs have stunning tones across their shells that consists of bright reds and blues. Others have pink or yellow markings that make for a beautiful contrast with white sands and black rocks.

In fact, as their shells get tougher, they also become brighter. Baby crabs have small red spots on their shells and, every time they molt their shell, the spots become larger until they acquire the typical adult coloring. When Sally Lightfoot crabs become adults, they are virtually predator-free!

Fun fact: a match made in heaven!
If you make your way to the Galapagos Islands, you could be witness to a postcard-worthy scene! While marine iguanas rest peacefully on the rocks by the beach, Sally Lightfoot crabs tend to climb on top of them and eat all the little parasites and fleas that have latched onto their dry skin.

How do Sally Lightfoot Crabs in Galapagos breed and reproduce?

Once the crabs mature, they breed throughout the whole year! As a matter of fact, males breed more frequently than females. Females carry the eggs in their stomachs until they are ready to hatch. When the time is right, they’ll release them into the water. The first phase of their life cycle is spent entirely in the ocean where they undergo several molts, adding more body segments and appendages with every molt. Eventually, the younglings undergo a metamorphosis process that will turn them into juveniles (the exact number of molts to get to this stage is still unknown).

As part of their health status, these crabs will molt throughout their life. When this happens, they get rid of their temporarily hard shell and become highly-prized soft-shell crabs (they remain in crevices and cracks of the rocks until the external shell gradually becomes harder), and repeat this process regularly.  The frequency of molting is related to growth. Therefore, a healthier Sally Lightfoot crab will grow faster and will molt more frequently. Simply fascinating!

Abandoned Sally Lightfoot crab shell

Sometimes, when exploring rocky coastlines, you may be lucky enough to find a recently abandoned shell. These crabs will leave that old shell perfectly intact, making you think the shell itself is still alive!

Where can I see Sally Lightfoot Crabs in Galapagos?

Hover your cursor or tap here to find out!

The best islands to see them are:

Española Island

Santiago Island

Fernandina Island

Floreana Island

San Cristobal Island

Apart from the Galapagos, they can also be found along the coasts of Central America, Mexico, and nearby islands.

So, will you be lucky enough to see these amazing crabs on your Galapagos cruise? Absolutely!

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