The Giant Coconut Crab

Blue Coconut Crab

Coconut Crab:

The coconut crab, Birgus latro, is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest land-living arthropod  on the world, and is probably at the upper size  limit  or  terrestrial  animal  with  exoskeletons  in  recent Earth atmosphere, with a weight of up to 4.1 kg (9.0 lb).  It can grow up to 1 metre (3 ft) in length from leg to leg. It is found on islands across the Indian Ocean and parts of the Pacific Ocean as far east as the Gambier Islands, mirroring the distribution of the cocnut palm; it has been extirpated from most areas with a significant human population, including mainland Australia and Madagascar.

Black Coconut Crab

The coconut crab is the only species of the genus Birgus, and is related to the terrestrial hermit crab of the genus Coenobita. It shows a number of adaptations to life on land. Like hermit crabs, juvenile coconut crabs use empty gastropod shells for protection, but the adults develop a tough exoskeleton on their abdomen and stop carrying a shell. Coconut crabs have organs known as "branchiostegal lungs", which are used instead of the vestigial gills for breathing. They cannot swim, and will drown if immersed in water for long. They have developed an acute sense of smell, which has developed convergently with that of insects, and which they use to find potential food sources. Mating occurs on dry land, but the females migrate to the sea to release their fertilised eggs as they hatch. The larvae are planktonic for 3–4 weeks, before settling to the sea floor and entering a gastropod shell. Physical maturity is reached after about 5 years, and the total lifespan may be over 60 years. Adult coconut crabs feed on fruits, nuts, seeds, and the pith of fallen trees, but will eat carrion and other organic matter opportunistically. The species is popularly associated with the coconut, and has been widely reported to climb trees to pick coconuts, which it then opens to eat the flesh. While coconut crabs can climb trees, and can eventually open a coconut collectively, coconuts are not a significant part of their diet. Coconut crabs are hunted wherever they come into contact with people, and are subject to legal protection in some areas.

Red Coconut Crab

Habitat:

Coconut piles provide food for young crabs as well as protection. Studies suggest that the larger crabs remain close to their burrows because they are already positioned in the best areas, where as small crabs will venture across an island in search of food or a better place to hide. As these animals grow in size, they depart from the safety of their existing burrow to find a larger place to live. Since coconut crabs are not depedent on snail shells for a home as the progress into adulthood, they are capable of growing to extremely large sizes. Coconut crabs are the largest terrestrial arthropods currently living on earth. Therefore, it is not surprising that the largest crabs, which are also the most dominant, live in the nicest burrows. 

Red Coconut Crab

Ideal burowing areas are those found in sandy soil because it is easier for a crab to dig. That is why smaller crabs often live closer to the coral edges of the island, where it is more difficult to build a nice burrow. The juvenile coconut crab diet differs from that of the adults, partly because of where they reside. The juveniles generally live under coconut piles or dense vegetation which provide the leaf and plant litter that they feed on. The adult coconut crabs are omnivores. They forage by night for fruits, rotting leaves, coconuts, and dead or injured animals, as well as other coconut crabs. Originally, coconut crabs were found on islands throughout most of the Indo-Pacific Region. The crab's slow rate of growth as well as late sexual maturity (six to eight years of age), has made them very susceptible to over exploitation. Recently they have become more rare because are a delicacy and have been captured at a quicker pace than they can reproduce. Coconut crab populations on Palmyra are high relative to other islands that they inhabit because the human threat is nonexistent.