LULU GARCIA-NAVARRO, HOST:
Imagine Christmas on Christmas Island.
(SOUNDBITE OF SONG, "CHRISTMAS ISLAND")
THE ANDREWS SISTERS: (Singing) How'd you like to spend Christmas on Christmas Island?
GARCIA-NAVARRO: Palm fronds, turquoise lagoons and a clattering army of crustaceans making their way from the island's forest to the beaches. Christmas Island red crabs - 50 million of them. Jahna Luke works for Christmas Island's tourism association and lives there. She says everyone has a hand in the crabs' journey.
JAHNA LUKE: We have all these measures in place to keep the crabs safe while they make their migration down to the ocean. Even cars on the island - we all have rakes in our cars so that on our way to work or wherever it is we need to go, we - we're out raking the crabs off the road to clear our way.
GARCIA-NAVARRO: Our apologies for the audio quality there. Christmas Island is 10,000 miles from our studios. So in case you didn't hear, there are so many crabs on the march that they have to rake them off the roads.
LUKE: I'm at my house at the moment, and I'm standing here with several crabs walking across our lawn.
GARCIA-NAVARRO: They're walking to the beaches to spawn, and that typically happens around Christmas. It's warm there on the Australian territory. It's in the 80s right now. But don't think about spreading your towel on the sand. For one thing, it's the rainy season, and for another...
LUKE: You literally can't find somewhere to put your foot on the beach. You're just standing there with these crabs crawling all over your feet.
GARCIA-NAVARRO: Christmas is a big deal, you can imagine, on Christmas Island, even though it's covered with crabs. British Captain William Mynors named it as he sailed past on Christmas Day 1643.
LUCY TURNER: They have a branch of the Australian post - so the post office - on Christmas Island. And they're quite famous that they have a whole line every year of Christmas Island crab stamps. And I think there's a whole load of stuff that goes along with that. You know, you can get your letter to Santa sent from Christmas Island.
GARCIA-NAVARRO: That's Lucy Turner, a marine biologist at the University of Plymouth. She says that during crab migration, they can walk nearly a mile a day, a long trek for a crab. Their hormones tell them to change their pace based on the weather.
TURNER: Depending on when the rains come, if they come late, they basically walk very quickly and in a very direct straight line to get to the ocean. If the rains come early and they have more time, they take their time. And they wander around, and they spend some time kind of taking that journey.
GARCIA-NAVARRO: For the most part, crabs are king on Christmas Island.
TURNER: As tends to happen in isolated islands, it's developed its own unique fauna and flora. And you know, like, the crabs, if you like, are the top predator. There's no big mammals that are going to harm you or hurt you in the jungle.
GARCIA-NAVARRO: So predators aren't a concern, just the island's 1,400 residents and their car wheels. Stay safe out there, crabs. And merry Christmas.
(SOUNDBITE OF SONG, "CHRISTMAS ISLAND")
THE ANDREWS SISTERS: (Singing) How'd you like to stay up late like the islanders do? Wait for Santa to sail in with your presents in a canoe. If you ever spend Christmas on Christmas Island, you will never stray, for every day your Christmas dreams come true. Transcript provided by NPR, Copyright NPR.