Minggu, 22 Februari 2015

Red Migration in Christmas Island

   Well Hello!So now i'm going to tell you about red crab migration phenomenon.This phenomenon is include to a biological natural phenomenon because it tells the life cycle of this species.Maybe some of you don't know,so i will try to make this writes clear to read for you.
    This phenomenon is most happen in Christmas Island in Australia.Red crabs are native to Christmas Island, Australia. The central plateau of Christmas Island is dominated by strands of rain forest. The island has a tropical climate and experiences both a wet season (December through April) and a dry season (May through November).

     More than 120 million red crabs can be found on the rain forest floor of Christmas Island. Red crabs live alone in dirt burrows, or deep rock crevices. Crabs stay in the shade of their dwelling for most of the year. In October or November, when the wet season is about to return, crabs begin their migration to the shore. This timing coincides with the lunar cycle and the tides.
      The crabs will start their migration if there is enough time for them to complete their downward migration, mate and develop eggs before the next suitable spawning date.The first action that occurs is movement of crabs to the sea. The largest mass movement of crabs takes place in this first downward migration. Males farthest inland start this movement and are progressively joined by more and more crabs (both males and females) as the movement progresses toward the sea.When the crabs arrive at the shoreline, they dip in the sea to replenish body moisture and salts.
     The male and female crabs then move back on to the shore terraces where the males dig burrows for mating. Mating takes place and then the males again dip in the sea and then they will start their return migration.Before the turn of the high tide and just before dawn the females will again move to the waterline and around the turn of the tide they will drop their eggs into the sea. After they have jettisoned their eggs the females commence their return migration.All phases of the crabs' breeding migration involve colossal numbers of crabs and usually occur all over the island.
        If the rains continue, there is usually a second, and sometimes even a third, smaller, downward migration by crabs that did not join in the first migration. When this happens it is possible to see crabs on return journeys mingling with the crabs on their downward migration. It can become confusing for all concerned! I'm so sorry that i can not be more explicit about the timing of the start of the red crab migrations, but the weather as you know cannot be accurately predicted. The best advice i can give is to be at Christmas Island during the last quarter of the moon in either November or December for the best chance of seeing something interesting happening in the annual red crab migration. If you are able to arrive earlier and to stay longer the more parts of the migration sequence you will be able to experience.
      I think that is all that i can share about this passage.Thx

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