Patchy rain has caused an interesting split in the red crab migration on Christmas Island – it means we’ll have two this year! Light rain at the end of October prompted what looked like a false start when some eager young males began marching up north. However the males reached the coastal cliffs and began dipping in the sea in preparation for mating. Quite a lot of females also joined them and the stage looks set for spawning – I think there will now be a healthy number of crabs set to spawn on the north coast at the end of this week.
The middle of November gave us some more really good rain – rousing the remaining red crabs from their burrows and off toward the ocean. These crabs have missed the November spawning window and will spawn at the end of December, so the island will have a split or double migration. This isn’t highly unusual but it hasn’t happened in the previous migrations I’ve seen. The rain has eased off again and the migrating crabs have halted their move to the coast for now, but they have plenty of time to make the 28 December spawning date so they are in no rush.
Once the crabs have made their way to the beach and mated the females need two weeks to develop/brood their eggs. Then with their load of ripe eggs the females gather at the edge of the ocean to drop their eggs in just before dawn as the tide turns and takes the eggs out to sea. The whole process is an exquisitely-timed feat of nature.
The crabs don’t discriminate when nature calls and can be seen crossing roads, as well as climbing kerbs, trees, doorsteps and people! Everyone on the island is helping to protect the crabs on the roads by driving slowly, steering around them when safe to do so and moving them from the road with rakes. What a great community we have out here!
Rob, Christmas Island National Park
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