One of the most spectacular natural processes on planet Earth began: annual red crab migrationin Australia. Over the next few weeks, millions of crustaceans will leave their forest burrows to head to the beaches of the Christmas Island with the aim of mating and laying eggs, that is, releasing their eggs.
According to the Christmas Island National Park website, migration begins with the first rains of the wet seasongenerally between October and November, although it may be delayed until December or January. All the crabs on the island leave their homes simultaneously to march towards the ocean.
The exact timing and speed of migration are determined by the moon phase. Impressively, the crabs know precisely when they must leave their burrows to meet this lunar date.
Millions of red crabs left their burrows in order to mate and release their eggs. Photo: Christmas Island National Park.If the rains come shortly before the optimal spawning date, they will move quickly, but if the rain falls early, they can take their timestopping to eat and drink on their way to the coast. If the rains come too late to meet the expected spawning date, some crabs will remain in their burrows and migrate the following month.
male crabs lead the migrationand the females join them on the way. Migration results in crabs swarming across roads, streams, rocks and beaches.
The march of the crabs: a journey to the sea
Los male crabswhich are larger, usually reach the sea first, although they are soon outnumbered by the females. After their arduous journey from the plateau, the crabs take a bath in the sea to replenish moisture.
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The migration of the red crab: a phenomenon that attracts tourists from all over the world
Subsequently, the males retire to the lowest terraces of the island to dig burrows. Due to the enormous number of crabs, the burrows are very close, which often leads the males to fight among themselves for possession of a shelter.
The females then join the males on the terraces to mate in or near the burrows. Once mating is complete, the male crabs take a second swim in the sea before beginning their journey home to the forest.
The migration begins with the first rains of the wet season. Photo: Christmas Island National Park.The females stay in the moist burrows. They produce eggs three days after mating. and remain in the burrow for about another two weeks while the eggs develop. Each female crab can produce up to 100,000 eggs, which she carries in a brood pouch.
When the moon reaches its last quarterthe females loaded with eggs leave their burrows and congregate on the coast. They cluster in shady places above the water line. In certain areas, it is possible to see up to 100 crabs per square meter of beach or rock.
Spawning always occurs before dawn, on a receding high tide, during the last quarter of the moon.
Male crabs, which are larger, usually reach the sea first. Photo: Christmas Island National Park.When the high tide begins to recede before dawn, the crabs move out to sea, release their eggs, and then return to the forest. Spawning can occur in five to six consecutive nights during the migration period.
The miracle of spawning: lunar synchronization and new life
Las red crab larvae They hatch immediately upon contact with water. Clouds of larvae swirl near the coast before being carried out to the open sea by the waves and ebbing tide.
The larvae grow through several larval stages over the next month, into shrimp-like animals called megalopods. The megalopods gather in pools near the shore for a day or two until they they turn into baby crabs fully formed and emerge from the water.
Red crab larvae hatch immediately upon contact with water. Photo: Christmas Island National Park.The tiny crabs, which measure around 5 millimeters widethey begin to march inland. It takes them about nine days to reach the safety of the plateau, where they will remain hidden in rock outcrops and forest debris for the first three years of their lives.
However, the vast majority of larvae never make it out of the water; They are devoured by fish, manta rays and the enormous whale sharks that visit Christmas Island to take advantage of this annual feast. Most years, very few, if any, baby crabs will emerge from the sea. However, once or twice a decade a huge number survive, enough to maintain the island’s large population of red crabs.
The migration of the red crab: a phenomenon that attracts tourists from all over the world
The red crab migration is Christmas Island’s biggest tourist attraction, attracting nature lovers from all over the world. The easiest places to observe migration and spawning are Drumsite, Flying Fish Cove, Ethel Beach y Greta Beach.
To protect the crabs, some sections of routes may be closed for part or all of the day at the peak of migration, Photo: Christmas Island National Park.To protect the crabs, some sections of routes may be closed for part or all of the day at the peak of migrationsometimes with little notice. However, visitors can park their vehicles and carefully walk through the sea of moving crabs. Crab bridges have also been built over the routes, which are great places to stop and watch the flow of crustaceans.
Visitors are urged to stay aware of road closures through the Christmas Island Road Access Board and through public announcements and local radio. Additionally, it is crucial to follow all instructions provided by staff and park rangers.
