EVERY summer, Christmas Island's motorists see red, but they don't suffer from road rage.
In fact, they are some of the most careful and courteous drivers in the world, making way for millions of red land crabs as they undertake their annual spawning migration.
And for the visitors who make their own migration to this isolated bit of volcanic rock in the Indian Ocean each November and December, the event is worth every kilometre travelled.
Estimates of the size of Christmas Island's red land crab population range from 60 million to more than 100 million.
If you split the difference at about 80 million, there are more than 50,000 for every person.
That's a lot of crustaceans but you won't see any red land crab banquets at local restaurants because the land variety lack the palatability of their ocean cousins and are worth far more as a tourist attraction than as a food source.
Their migration is awe-inspiring, not only for its scale but also for the complexity of the breeding process which is triggered by the start of the rainy season.
This year, the rains came early and the crabs took their time, sauntering down the hills.
When the rains come late, it's a mad dash for the shore.
Once the rains begin, the males leave their forest burrows and head to the shore where they dip in the ocean before finding a suitable spot on the terraces to dig a mating burrow.
Then the females follow, also taking a dip in the ocean before mating.
The expectant mums then spend about two weeks brooding their tiny eggs in the mating burrow.
The spawning comes to a climax when the females emerge from their burrows and gather at the shore to release their eggs into the ocean.
They do a special dance, nicknamed the crab disco, to empty their eggs from their brood pouches.
Pincers raised in the air, the females shake like belly dancers with no sense of rhythm, and a dark cloud of eggs disappears into the waves.
The timing of the spawning is crucial, and visitors cannot reliably plan a trip until the rainy season starts.
The female crabs only release their eggs before dawn during the full moon and the outgoing tide, giving their eggs the best chance of being swept out past the reef and its gauntlet of predators and into the open ocean where they go through larval stages before turning into miniscule replicas of their parents.
If all goes well, the baby crabs return to the island three to four weeks later, their shells quickly turning from translucent to pink and, eventually, red.
Some years, heaps of babies return, covering the shores in a fine pink tide. Other years, like this one, hardly any come back.
“It can be a smattering of crabs or it can be wall-to-wall,” said Christmas Island National Park ranger Max Orchard, who has been monitoring the spawnings for the past 20 years.
“They're sort of at the mercy of the wind and tides and the sea.”
I am slightly disturbed when Max tells me adults will eat the babies, but it's part of their natural lifecycle.
What's not natural is an introduced species of ant, the yellow crazy, which is the greatest threat.
While vehicles kill an estimated half a million crabs each year, the ants have reduced the population by as much as a third.
“The ants don't actually attack but what they do is displace the crabs from their burrows,” Max said.
“The crabs require a level of humidity to stay alive and what happens during the dry season is they (displaced crabs) dehydrate and die.”
Parks rangers have found a bait that works on the ants, but unfortunately it also kills crabs and can only be used in areas completely dominated by the ants. Max tells me they are investigating a biological control, where they reduce ant numbers by eliminating a sugar-producing insect, also introduced, which the ants rely on for food.
Of course, to a first-time visitor, there seems to be no shortage of crabs. They're everywhere, scratching at my hotel door and testing my driving skills as I slowly zigzag along the roads (the few that are open this time of year).
What surprised me was the lack of throngs of tourists lining Ethel Beach, one of the best places to view the spawnings by torchlight.
While National Geographic's Great Migrations series certainly increased international awareness of the spawning, visitor numbers are limited by accommodation.
IF YOU GO
Getting there: Virgin Blue Airlines offers direct flights from Perth to Christmas Island on Thursdays, Fridays and Saturdays with fares starting from $464 per person, one way online. Flights from Christmas Island to Cocos Keeling Island are also available on Saturdays and return from Cocos Keeling Island to Christmas Island on Tuesdays, with fares starting from $194, per person, one way online.
Where to stay: The Sunset and VQ3 Lodge are within walking distance to Flying Fish Cove, the grocery store, tourism office, pubs and restaurants.
To see Seanna's video of December's crab spawning, go to www.vimeo.com/18357861
For more information, go to www.christmas.net.au.
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