Red King Crabs typically walk sideways (a behavior 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 walk forwards or backwards, including raninids,
Libinia emarginata and Mictyris platycheas. Some crabs, notably the Portunidae
and Matutidae, are also capable of swimming, the Portunidae especially so as
their last pair of walking legs are flattened into swimming paddles. Crabs are
mostly active animals with complex behavior 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. Fiddler crabs (genus Uca) dig burrows in sand or mud, which they
use for resting, hiding, mating and to defend against intruders