A Tiny Island. Millions of Crabs. Terrifyingly Awesome Photos.

But climate change could disrupt their spectacular annual migration.


An Australian wildlife official inspects migrating red crabs on Christmas Island, in 2013. Xu Yanyan/Xinhua/ZUMA

This month, an eerily precise annual migration began in earnest on a tiny Australian island about 500 miles off the coast of Indonesia.

Every year, millions of adult red crabs—first the males, then the females— scamper out from Christmas Island’s central forests, across the island, and finally to beaches that meet the Indian Ocean. Their goal is to stage one giant crab sex party: to mate and spawn.

The local government has constructed underground crab-ways to accommodate the migration. Parks Australia

According to Christmas Island National Park authorities, “the females will spend two weeks brooding their eggs before making their way to the cliffs and beaches to spawn. This should occur about the 18th-19th of December. Before sunrise on these mornings the females will release their eggs into the ocean—timed perfectly for the receding tide.”

Amazing.

Watch them below making their slow, deliberate, hard-wired journey:

So. Many. Crabs. Max Orchard/Parks Australia

Parks Australia says that there are tens of millions of crabs—20 species in total—that live on the island. Their migration occurs between October and December and is triggered by rains characteristic of the island’s tropical wet season.

The local government closes roads for the invasion to prevent the little guys from getting squashed by cars. Xu Yanyan/Xinhua/ZUMA

Max Orchard/Parks Australia

Ruling the island! Crab Power! Xu Yanyan/Xinhua/ZUMA

Wildlife rangers have installed up to 7.5 miles of crab fences along the roads, according to Parks Australia—and every year they add up to three miles of additional temporary fencing—to help protect the crabs and their mating rituals. There are already 34 “crab crossings,” which are basically culverts under the roads so the crabs can avoid the cars. Here’s a video explaining just how elaborate the preparations have become:

Behind the scenes of the red crab migration – Christmas Island 2012 from Parks Australia on Vimeo.

But this spectacular beach invasion may be threatened by global warming. Research conducted by Princeton University found that increasingly unpredictable rainfall—potentially a symptom of climate change—could harm the red crustaceans’ chances of a successful journey, and therefore  imperil their survival.

The study, published in Global Change Biology, found that if fluctuations in rainfall become more extreme and frequent, the crabs might get scrambled and not even start their migration, which is what happened during an exceptionally dry 1997 season. “We found that the start date of the migration was really dependent on the rainfall they received in the weeks before the migration,” said Allison Shaw, an author of the study, and now an assistant professor at the University of Minnesota. “The issue for the crabs is that they have to migrate if they want to produce. If they can’t make it to the water, they won’t produce offspring.” Disturbances in the migration patterns were linked in particular to strong El Niño years, which tend to make Christmas Island dry, Shaw says.

There’s still a lot of science yet to be done to clear up the connection between El Niño and climate change, but trends are emerging. “The 20th century is significantly, statistically stronger in its El Niño Southern Oscillation activity than this long, baseline average,” Kim Cobb, Associate Professor of Climate Change at the Georgia Institute of Technology, told me last year. That is, El Niño events have gotten worse.

If that’s the case, Christmas Island, home to the crabs, will experience more intense, and therefore drier periods, says Shaw. A lack of rain can delay or entirely cancel the crimson tide of crabs, and the resulting swarms of crab offspring, seen below.

Finally, waves of baby crabs appear. Parks Australia

Parks Australia

More Mother Jones reporting on Climate Desk

AN IMPORTANT UPDATE

We’re falling behind our online fundraising goals and we can’t sustain coming up short on donations month after month. Perhaps you’ve heard? It is impossibly hard in the news business right now, with layoffs intensifying and fancy new startups and funding going kaput.

The crisis facing journalism and democracy isn’t going away anytime soon. And neither is Mother Jones, our readers, or our unique way of doing in-depth reporting that exists to bring about change.

Which is exactly why, despite the challenges we face, we just took a big gulp and joined forces with the Center for Investigative Reporting, a team of ace journalists who create the amazing podcast and public radio show Reveal.

If you can part with even just a few bucks, please help us pick up the pace of donations. We simply can’t afford to keep falling behind on our fundraising targets month after month.

Editor-in-Chief Clara Jeffery said it well to our team recently, and that team 100 percent includes readers like you who make it all possible: “This is a year to prove that we can pull off this merger, grow our audiences and impact, attract more funding and keep growing. More broadly, it’s a year when the very future of both journalism and democracy is on the line. We have to go for every important story, every reader/listener/viewer, and leave it all on the field. I’m very proud of all the hard work that’s gotten us to this moment, and confident that we can meet it.”

Let’s do this. If you can right now, please support Mother Jones and investigative journalism with an urgently needed donation today.

payment methods

AN IMPORTANT UPDATE

We’re falling behind our online fundraising goals and we can’t sustain coming up short on donations month after month. Perhaps you’ve heard? It is impossibly hard in the news business right now, with layoffs intensifying and fancy new startups and funding going kaput.

The crisis facing journalism and democracy isn’t going away anytime soon. And neither is Mother Jones, our readers, or our unique way of doing in-depth reporting that exists to bring about change.

Which is exactly why, despite the challenges we face, we just took a big gulp and joined forces with the Center for Investigative Reporting, a team of ace journalists who create the amazing podcast and public radio show Reveal.

If you can part with even just a few bucks, please help us pick up the pace of donations. We simply can’t afford to keep falling behind on our fundraising targets month after month.

Editor-in-Chief Clara Jeffery said it well to our team recently, and that team 100 percent includes readers like you who make it all possible: “This is a year to prove that we can pull off this merger, grow our audiences and impact, attract more funding and keep growing. More broadly, it’s a year when the very future of both journalism and democracy is on the line. We have to go for every important story, every reader/listener/viewer, and leave it all on the field. I’m very proud of all the hard work that’s gotten us to this moment, and confident that we can meet it.”

Let’s do this. If you can right now, please support Mother Jones and investigative journalism with an urgently needed donation today.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate