Coconut Crab

Behaviour
Crabs typically walk sideways (a behaviour which gives us the word crabwise). This is because of the articulation of the legs which makes a sidelong gait more efficient. However, some crabs prefer to walk forwards or backwards, including raninids, Libinia emarginata and Mictyris platycheles.. Some crabs, notably the Portunidae and Matutidae, are also capable of swimming.
Crabs are mostly active animals with complex behaviour patterns. They can communicate by drumming or waving their pincers. Crabs tend to be aggressive towards one another and males often fight to gain access to females. On rocky seashores, where nearly all caves and crevices are occupied, crabs may also fight over hiding holes.