Robber Crab (Birgus latro)


Class: Crustacea
Order: Decapoda
Family:    Coenobitidae
Size:    Length: Up to 24 inches (61 cm)  from head to tail
Weight: 6 to 25 pounds (2.7 to 11 kg)
Diet: Coconuts, other fruit and vegetation
Distribution: Islands in the Indian and Pacific ocean
Young:  Hundreds of eggs, once per year 
Animal Predators:  Unknown
IUCN Status: Data Deficient
Terms: No special terms
Lifespan: 40+ years old



·       Robber crabs are also known as “coconut crabs.”

·       They are the largest and heaviest land crabs.

·       Robber crabs drink by picking up water drops with their claws and holding them up to their mouth.



Robber crabs are related to hermit crabs and are even known as hermits by some, but they are not true hermit crabs because they only wear a shell for a short time during their first year. They have enlarged, modified cavities that act as lungs so that they can breathe air. 



Robber crabs lives on islands found in the Indian and Pacific oceans, including parts of the Japanese Ryu Kyu islands, Australia, the Solomon Islands and Fiji. They need to live in areas with high humidity and warm temperatures, from 73 to 84°F (23 to 29°C). After their first year they live only on land and will drown if submerged in water for more than a few minutes.


Feeding Habits

Robber crabs are excellent climbers and will ascend trees to snip off coconuts or other fruit, such as papayas, with their large pincers. They then descend backwards down the tree to the ground and scoop up the food they have knocked down. The coconuts usually split when they fall onto the ground, and the robber crabs, who are extremely strong, have powerful pincers that enable them to further open up the split coconuts by pounding and/or chipping at them. Coconuts are their favourite food, but they eat just about any type of fruit and vegetation. 



Robber crabs are born in the sea, but leave to live on land and only return to spawn. Mating occurs from May to September, and the female carries her eggs in her abdomen for several months, and then returns to the sea to lay several hundred eggs that hatch into larvae instantaneously. After 20 to 30 days, the larvae develop into another stage and leave the water. On land, they move into a seashell for the next three to four weeks. They then reject the shell and bury themselves in moist sand for their transformation into adults. 



They are nocturnal animals, resting in their burrow during the day and then coming out at night to search for food.



Robber crabs have disappeared from much of their previous range and are extremely rare in areas where humans are abundant. Because they are easily caught, robber crab populations are quickly declining. Some islands where they are found have areas in which they (and other aquatic creatures) are protected. The IUCN lists them as Data Deficient, which means that there is not enough data concerning their abundance and/or distribution to assess their risk of extinction. 



Robber Crab Wildlife Fact File, IM Pub, US