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.
This video documents the second stage of the red crab migration, after the crabs have mated and before the eggs hatch in the ocean. At the start of this stage, females brood their eggs in dirt or coastal rock burrows for 12 to 13 days. A female red crab can lay up to 100,000 eggs, which she holds in her abdominal sac. With the arrival of the waning moon, females make their way into the sea. In what looks like a dance, females brace themselves at the waters edge, and release their eggs.
How many eggs can a female crab produce?
How many days does the female red crab sit with her eggs?
What cues the red crabs to lay their eggs and begin migration?
What kind of tide is best for the female crabs to release their eggs?
Do most of the eggs survive to return as hatchlings?
Term Part of Speech Definition Encyclopedic Entry animal migration Noun
process where a community of animals leaves a habitat for part of the year or part of their lives, and moves to habitats that are more hospitable.
small hole or tunnel used for shelter.
type of marine animal (crustacean) with a flat body, hard shell, and pincers.
steady, predictable flow of fluid within a larger body of that fluid.
Encyclopedic Entry: current lunar cycle Noun
complete cycle of visible phases of the moon, approximately 29.5 days.
movement of a group of people or animals from one place to another.
large body of salt water that covers most of the Earth.
Encyclopedic Entry: ocean offspring Noun
the children of a person or animal.
large region that is higher than the surrounding area and relatively flat.
Encyclopedic Entry: plateau rain forest Noun
area of tall, mostly evergreen trees and a high amount of rainfall.
Encyclopedic Entry: Rain forest tide Noun
rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.
Encyclopedic Entry: tide