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 third and final stage of the red crab migration, after the eggs have been released into the ocean. The crab larvae remain in the water for about a month, growing through several larval stages. Few are able to survive the harsh ocean currents and marine predators. Those that survive shed their larval casing and begin the journey back into the rain forest, battling predators, such as the yellow crazy ant, along the way.

 

  1. How long do the red crab eggs drift in the ocean?

    • Answer

      Red crab eggs drift in the Indian Ocean for about three weeks. During this time, the eggs hatch and morph into larvae.

  2. What guides young red crabs on their migration route?

    • Answer

      Young red crabs are driven by instinct to trace the path of their ancestors.

  3. What hazards do red crabs face at sea? What hazards do they face on land?

    • Answer

      At sea, red crabs risk being swept away by the currents or eaten by predators. On land, red crabs must survive predators such as the yellow crazy ant.

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.
burrow
Noun

small hole or tunnel used for shelter.
crab
Noun

type of marine animal (crustacean) with a flat body, hard shell, and pincers.
hatch
Verb

to emerge from an egg.
hazard
Noun

danger or risk.
Indian Ocean
Noun

one of Earth's four oceans, bordered by Africa, Asia, Australia, and Antarctica.
instinct
Noun

natural motivation or behavior.
larva
Noun

a new or immature insect or other type of invertebrate.
lunar cycle
Noun

complete cycle of visible phases of the moon, approximately 29.5 days.
migration
Noun

movement of a group of people or animals from one place to another.
ocean
Noun

large body of salt water that covers most of the Earth.
plateau
Noun

large region that is higher than the surrounding area and relatively flat.
predator
Noun

animal that hunts other animals for food.
rainforest
Noun

area of tall, mostly evergreen trees and a high amount of rainfall.
tide
Noun

rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

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    Editor

    Caryl-Sue, National Geographic Society

    Page Producer

    Makayla Trotter

    Producer

    Nina Page, National Geographic Society

    Last Updated

    Jan. 19, 2012

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