Other Crabs – The Christmas Crabs (Gecarcoidea natalis)
The Christmas Crabs are found on Christmas Island and are one of a few species of crabs that call dry land thier home. Approximately 44 million Christmas Crabs live on Christmas Island but accidental introduction of the Crazy Ants (yellow) is commonly believed to have killed off approximately 15 million of the Christmas Crabs in the recent years.
Christmas Crabs are larger than most crabs. Their carapace can reach 4.6 inches wide. The claws are thick and red along with most of their body. Due to their red hue, they are most commonly known to natives as ‘red crabs’.
Christmas Crab Behaviour
The Christmas Crabs are land crabs trained through evolution. They breathe through their gills like all other land crabs. This means they are always a short distance away from a water source so they can soak their gills and continue breathing. If not, their gills dry up and breathing becomes extremely difficult resulting in loss of oxygen and death. These crabs are mainly active during the day so they take care as to not stay in direct sunlight. They can be found rummaging the grounds under tree bark, leaves and other shady places for food.
The Christmas Crabs are omnivorous scavengers. Their diet mainly consists of fruits, flowers and leaves unlike their cousin the Dungeness Crabs who would eat fellow fallen crabs if the opportunity arises.
During the dry season, Christmas Crabs will dig a small hole in the soft moist ground to call their home. They can usually stay buried for up to three months until the wet season arrives. Christmas Crabs live a solitary life and, apart from breeding, are aggressive with intruders that wander close to their burrows.
Christmas Crab Breeding/Migration
The Christmas Crab calls the forest its home but they breed by the coast of the Island. By the millions they travel across the island to their breeding grounds. Their journey is made dangerous due to man-made terrain, yellow crazy ants and the red hot sun. Hundreds of thousands of Christmas Crabs are killed but their young must hatch by the ocean. It is a brutal month long migration, up to five miles. They stop to nourish themselves wherever and however they can. The lucky ones that make it to the coast replenish themselves with the cool salt water. The lucky few will be pulled into the ocean by the strong waves.
The surviving male Christmas Crabs, during this time, will dig snug burrows and wait patiently for the females to arrive. The female will choose her mate and begin breeding. Once done, the male will begin his journey home back into the forest. The female will descend into the burrow. She will brood for a week until her eggs are ready. Eggs stowed in the sack, the female Christmas Crabs will make their way to the sea. Many will drown in the attempt to launch their eggs into the sea. Many eggs will be food for the coastal creatures. But the sheer number of the eggs will allow millions to survive and the baby Christmas Crabs will migrate back into the forest and begin their new lives.