Crabs
Crabs (Decapod crustaceans) Overview
There are almost 200 species of crabs in Hawaii. The scientific name of crabs is decapod crustaceans, a name that applies to true crabs, which typically have a very short projecting tail or a short abdomen that’s hidden under the thorax. Other animals with similar names, such as hermit crabs, are not true crabs.
Many crab species walk sideways, but not all. They can communicate among each other by waving or drumming their pincers. They are often times aggressive toward each other and male crabs sometimes fight over female crabs or hiding holes.
Crabs are omnivores and primarily eat algae, but also other foods that they find, including bacteria, fungi, worms and other crustaceans.
Frequently Asked Questions
How many crab species are found in Hawaii?
There are nearly 200 species of crabs in Hawaiian waters, ranging from small intertidal crabs to larger reef and deep-sea varieties.
What are "true crabs"?
True crabs, or decapod crustaceans, have short, tucked-in tails beneath their bodies. This separates them from similar species like hermit crabs, which are not considered true crabs.
Do all crabs walk sideways?
No. While many crab species walk sideways due to their leg orientation, not all do—some walk forward or in a more circular motion depending on their body structure.
How do crabs communicate?
Crabs use visual signals such as waving or drumming their pincers. These behaviors can communicate territory, mating interest, or warnings to other crabs.
What do crabs eat?
Crabs are omnivores. They primarily eat algae but also consume bacteria, fungi, worms, small fish, and even other crustaceans when available.