What land animal hitchhikes on drifting coconuts?
By Chelsie Vandaveer
November 21, 2001
killerPlants Tendrils: ~~1~~2~~3~~4~~5~~
Suggested Reading—>Click here.
Buy: Coconut shell sculpture, Coconut seed necklace—>Click here.
The coconut palm (Cocos nucifera) is the best known of the drift fruits, those seeds that travel the oceans colonizing new lands. The coconut, though, has not traveled alone. It has served as a raft carrying a hermit crab. An unlikely pair of voyagers: an embryo plant inside the husk and a tiny crab clinging to the outside.
The coconut crab is capable of climbing the trunk of the coconut palm to get to its main food. The crab selects a coconut and using its chelae (pincers) cuts the coconut free. The crab descends from the palm and pries the husk from the coconut. After the husk is removed, the crab pounds the coconut against a rock until it breaks open. It may take the determined crab two days to open the coconut; often it must stop to defend its prize from other crabs.
The coconut crab (Birgus latro) begins its life as a larva in the ocean. It is no more than another tiny life form in the world of plankton. After several moltings, it leaves the sea to become a land crab. A few coconut crabs have made it to other islands while still larvae. But to colonize isolated islands, the crabs must have arrived by rafting.
Coconut crabs are the largest of the hermit crabs. They can grow to 75 centimeters (almost 30 inches), weigh up to 4 kilograms (8.8 pounds), and live 50 years. Unlike most hermit crabs that need to occupy a mollusk shell, the coconut crab forms a hard carapace to
protect its abdomen.
The coconut crab has adapted to natural environmental pressures. On small islands where there are no people, the crab is diurnal, active during the daylight hours. But where humans are present, the crab is nocturnal (active at night). On some islands, the crab has altered its diet from coconuts to lau hala (Pandanus tectorius), another fruit whose seeds drift on the ocean currents. Coconut crabs with a main diet of coconuts are blue and lavender. Crabs with a diet of mostly Pandanus are bright orange.
But humans have put too much pressure on the crab population. Coconut crabs are now rare creatures and on some islands have been extirpated (locally extinct). Their habitats have been destroyed and they have been over-collected. Coconut crab meat is considered a delicacy and brings a high profit. Hunters often ignore the laws meant to protect this remarkable creature.
To view a photograph of a close relative of the lau hala, click on the link:
Plant of the Week, Pandanus utilis, October 15, 2001.
killerPlants Tendrils: ~~1~~2~~3~~4~~5~~
Suggested Reading:
What palm has more uses than any other plant? Plants that Changed History - November 20, 2001
What palm produces ivory? Weird Plants - May 13, 2004
What is a toddy? What's in a Name? - January 2, 2004
What is carnauba? Plants that Changed History - March 2, 2004
What was the drunken date palm? Herbal Folklore - December 29, 2003
How was the spiny gru-gru utilized? Herbal Folklore - January 3, 2005
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