These crabs with flat, squarish bodies and flat pointed legs are common in many of our mangroves. They have a net-like pattern on the sides of the body next to the mouth parts which help recirculate and oxygenate water in the gill chambers so that they can breathe air and stay out of the water for some time.
Many are burrowers, digging holes at the base of mangrove trees and in mud lobster mounds. At high tide during the day, tree-climbing varieties are often seen clinging to tree trunks just above the water line. Here they remain motionless. They probably do this to avoid both aquatic predators in the water, as well as airborne predators such as birds.
The Teochew pickle these crabs in black sauce with vinegar and eat them with porridge hence it is also called vinegar crab. They are considered pests in mangrove plantations because they attack mangrove seedlings.
Location
Sungei Buloh Nature Park
Singapore
January 2009