Behind the scenes of the red crab migration, October 2012


Discover the hard work that goes into preparing for the mighty annual migration of Christmas Island's red crabs. Park staff set up temporary fencing to keep crabs off the roads and funnel them to special crab crossings. The crossings need to be cleared of a year's worth of debris in order to be effective.

Staff and locals alike man the roads with garden rakes to help keep the crabs out from under the cars. This huge effort has resulted in a lot more crabs safely reaching the coast to spawn.



It’s mid-October on the remote Australian outpost of Christmas Island, and the dry season is at its peak. The forest wilts under a scorching sun that has baked the island dry.
But any day now, the wet season could begin without warning. And when it does, it will trigger the resident land crabs - all 50 million of them - to begin their great migration, from the centre of the island to the sea.

For the rangers at Christmas Island National Park, there’s a lot of work to be done - and quickly. The crustacean horde has no sense of road safety, so the rangers must go to great efforts to protect the crabs from traffic - and to protect the traffic from the crabs.

The first line of defence is crab fencing, to keep the crabs from the roads. There are around 12 kilometres of permanent aluminium fencing along the island’s roads, but each year the rangers must set up an additional five kilometres of temporary fencing in very specific places.

As the migration progresses, this temporary fencing will be moved again to assist the crabs on their return journey, after they have completed their breeding cycle. The rangers must work fast to get all the crab fencing in place.

The fences funnel the marching crabs to underpasses, allowing them to cross beneath the road, avoiding the traffic.

These so-called ‘crab grids’ are only effective if they are clear and free from debris and dirt. Each and every grid section needs to be removed so that the dirt and leaves can be excavated from the underpass.

A year’s worth of accumulated debris need to be cleaned from 34 crab crossings. It’s a mammoth task, and with the wet season rains threatening to break any day, the rangers work tirelessly to ready the roads for the impending crab influx. Fortunately, the local traffic is courteous.

And that’s not the end of it. When the migration starts, the rangers will be busy closing roads and leading vehicle conveys through key areas.

It will be all hands on deck for all the other park staff too, raking the crabs off roads that can’t be closed or fenced, so that cars can still get through.

The national park aims to minimise the roadkill that inevitably occurs each migration. Thanks to the crab fences and crab grids, the support of the local community and the co-operation of road users, this goal is being met.

The scenes in old documentaries of cars crunching their way down crab-covered roads are fortunately now memories of the past. Today, the crabs are respected and their migration is appreciated for the wondrous spectacle that it is.


Footage supplied by:
Braydon Moloney