Christmas Is is home to about 180 types of crabs. 20 of them have evolved into land crabs, allowing them to live the majority of their life on land, scavenging among fallen leaves and burrowing into the soil for homes, only to return to the sea for spawning.
RED CRABThe most famous of the land crabs is the Red Crab (
Gecarcoidea natalis). Endemic to Christmas Is, their migration is one of the ecological wonders of the world, carpeting the island with a fabric of red. Generally bright red, though there are the occasional orangy or purplish varieties. They're active scavengers in the day (and not at night as do most crabs) and feed on fallen leaves, fruits, flowers and seedings...and true to their scavenging character, are open-minded to feeding on dead comrades as well.
They've been acknowledged as a major determinant of forest structure and composition and thus, play a crucial role to the ecological stability of the island. (The future of the Red Crabs is now clouded by the joint effect of human impacts and the infestations of the Yellow Crazy Ant, an accidental introduction into Christmas Is)
Migration usually coincides with the raining season, starting around late Oct and ends about early Jan. However, the drier weather pattern had resulted in late starts in the migration for 2006 and I was rewarded with them still in the midst of migration. Unfortunately, I never did catch sight of them spawning; fellow travelers at another location were luckier.
RED CRAB CYCLE:
Nov-Dec
1. Adult males and females move down to dip in the ocean and mate
2. Females retreat to freshly dug burrows (by the males) for 12-13 dys to develop up to 100000 eggs
Dec-Jan
3. Females release eggs into the sea on the turn of a pre-dawn tide
4. Eggs hatch immediately. Larvae live in sea for 1 mth
5. Larvae become gill-breathing megalops
6. Megalops leave water, moult into air breathing small crabs and migrate inland
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