The 73rd anniversary of our annual Independence Day celebrations was proudly celebrated on the 4th of February. Due to the training sessions of the three Armed Forces and other cultural events that usually take place on that day, it is common to have to follow a special traffic plan for a few days before the Independence Day celebrations. Due to the closure of certain roads, many visitors to Colombo have to use alternative routes to reach their destination. Although we have to adapt to a special traffic plan only for Independence Day or Labor Day, can you imagine a group of islanders following a special road plan because of a parade of red crabs? It is, in fact, a very natural and wonderful natural phenomenon. This parade of red crabs can be seen on Christmas Island.
Burning red crab king
Christmas Island is a small island in the Indian Ocean about 360 km south of the Indonesian island of Java and about 1400 km northwest of Australia. Administered by Australia, the island’s population is close to 1900, and most of the island’s are of Chinese descent. Christmas Island is also home to people of European and Malay descent. These settlers are descendants of workers who once came to the island for phosphate mining.
With scenic beaches as well as tropical climates and lush forests, Christmas Island covers 63% of its land area. In addition to the rare species of flora and fauna, these forests, full of beautiful waterfalls, also provide habitat for our protagonists, the red crabs.
Commonly known as “Christmas Island Red Crabs”, the scientific name for this terrestrial crab species is Gecarcoidea natalis. They have been identified as endemic to the jungles of Christmas Island. These slightly larger crabs are more active during the day, but can even die from direct exposure to the sun. Therefore, they prefer to stay in shady places to protect their body moisture. Depending on fallen leaves, seedlings, fallen fruits and flowers, they act as pollutants, contributing to nutrient recycling and promoting the spread of island plants. Therefore, their role in the forest system of Christmas Island is unique and crucial.
Because of their sensitivity to moisture, they spend most of the year living in burrows dug in the interior of the forest. In order to retain more moisture in the burrows when the dry season approaches, they tend to cover the entrance to their burrows and stay in these houses for about three months until the next rainy season begins. Although red crabs are generally considered to be solitary animals, as soon as the breeding season arrives, these solitary animals become a great community, turning the entire island into a red carpet!
Red march towards the sea
October to November is an important time of year for Christmas Island crabs as well as their islanders. The red crabs prepare for their breeding season during the humid climate of the island. Although red crabs live at a loss in the wild for most of the year, they migrate to the coast during their breeding season and take over the entire island, showing the world who the real owners of the island are.
This breeding work of theirs is closely related to the lunar calendar, or phases of the moon. Once the red crabs migrate to the coast, they mate for at least a week. Leading this massive migration of millions from the forest in the center of the island to the coast are mostly male crabs, who come ashore before the female crabs, dig burrows and try to protect their habitat from other male crabs. Although the male crabs migrate back into the wild after mating near the excavated nest, the females remain in the nest for an additional period of time to produce and preserve eggs. It is interesting to note that these females are careful enough to release eggs into the sea only during the period between the last quarter of the lunar calendar and the new moon. During this time the tides rise and the eggs are easily accessible to the sea. But if the weather changes during that time, they may even postpone spawning until the next lunar month.
The hatchlings live at sea for about a month before returning to shore, and then begin migrating back into the wild to complete the rest of their life cycle.
The threat of the Yellow Cross
Red crabs, which live in a peaceful and isolated ecosystem, have no natural predators in the terrestrial environment. But between 1915 and 1934, this peaceful red crab suffered a setback due to an invasive species of ants called “Yellow Crucifix”. By the 1990’s, millions of ants had settled on the island.
Yellow Crocodile ants defend themselves by injecting formic acid into the threat. Formic acid can kill crabs. Researchers at the University of La Trobe in Melbourne believe that these ants have killed millions of red crabs since they arrived on Ants Island. They warned that this could have a devastating effect on the island’s ecosystem.
The first method used to fight the invading Yellow Crass ants was to poison their colonies. But later, scientists introduced a small species of antelope to the island, destroying the ants’ main food source. Although the Yellow Cruise ants could not be completely eradicated from the island, scientists were able to preserve the ecological balance of Christmas Island and protect the red crab population.
Islanders greet crab parade
Once upon a time, these red crabs, which were on the innocent journey of millions for their breeding work, faced many dangers with the arrival of human habitation. Crossing the road, they were at risk of being killed by thousands of vehicles, and their skeletons were strong enough to pierce the wheels of vehicles.
However, due to the ecological importance and tourist attraction of the time, a number of remedies are being implemented on the island to avoid any inconvenience to crabs and humans during the migration season. During this time the park is closed to tourists, and many roads are closed as the roads are covered with crabs that look like a red carpet. Even from the islanders, the journey to the future upliftment of this innocent living community is a blessing in disguise. Some people remove the crabs safely and attach the covers to the front wheels of their vehicles.
In addition, aluminum barriers have been erected on the island to allow migratory crabs to cross the road and cross the road via crab bridges.
Also, during migration, people on both sides of the road are accustomed to wetting these crabs, which release moisture, to prevent dehydration. Christmas Island is known around the world for its large annual migration of millions of crabs, which attracts a significant number of tourists between October and November.
However, at a time when thousands of species are threatened with extinction due to human activities, it is truly commendable that Christmas residents have even closed their highways and partially contributed to this crab parade.