A Sea of Red: The Epic Migration of 100 million Red Crabs on Christmas Island

Christmas Island Red Crab Migration Photo Parks Australia

Posted December 9, 2024

Getting your Trinity Audio player ready...

What is the first thing coming to your mind when you hear the name Christmas Island?

The island may sound festive by name, but it is a tropical paradise, fringed by palm trees and edged by sandy beaches that indent the rugged coastline. Captain William Mynors of the British East India Company discovered Christmas Island on December 25, 1643. The date probably gives away why the island is called Christmas.

Red Crab is Endemic to Christmas Island

Even though it is an Australian territory, Christmas Island exists geographically closer to Java of Indonesia than to Australia. Between October and January each year, the island is overtaken by swarms of red crawlies, a sight that could give you goosebumps and leave your jaw on the floor at the same time.

“The red crab, endemic to Christmas Island, is the most abundant of the more than 20 species of land crab on the Island,” says Brendan Tiernan, Senior Threatened Species Program Coordinator at Christmas Island National Park.

“The iconic red crabs continue to thrive here due to the island’s unique combination of dense rainforest, rocky cliffs, and sandy beaches,” Brendan adds.

Big red crab on rake. Credit Parks Australia

The Spectacular Nature Migration Spectacle

The crabs live in the forest, but once a year, when the rainy season begins, they migrate to the sea to breed. To witness this awe-inspiring nature spectacle, come to the island between October and January when the precipitation is at its highest. The moisture in the air helps them breathe through their gills.

During these months, as many as 100 million red crabs scuttle into every crevice of the island. Roads are closed to provide a safe passage for the crabs. They can even find their way into homes—beds, bathtubs, rooftops, and gutters.

These Little Crawlies are Everywhere, but They Are Harmless

“It’s common for locals to share funny stories about where crabs have ended up. I’ve heard of crabs finding their way into toilets, beds, roof cavities, and even fridges!” Brendan says. “Fortunately, locals are proud and highly protective of these little red scuttling creatures that make the island famous. Despite their intimidating claws, they are gentle creatures, easily moved by scooping them into a dustpan and moving them outside.”

The red crab migration period is also a busy season for volunteers and park rangers, who are on constant duty, sweeping crabs off the roads with rakes. The local authority even builds “crab bridges,” long, narrow overpasses spanning roads to help crabs cross safely.

“Parks Australia’s Christmas Island staff work with the community, the Shire of Christmas Island and the Australian Federal Police to prepare and manage the wildlife spectacle,” Brendan explains. “Warning signs and road closures help redirect traffic, and temporary barriers guide millions of crabs to underpasses and overpasses.”

Once they reach the coast, female crabs release their eggs into the ocean. After spawning, the crabs head back to the forest, while the larvae hatch, develop, and eventually drift back to the shore as baby crabs.

“The 2023-24 migration was different in that it wasn’t simultaneous across the entire island. Instead, the crabs responded to patchy rainfall, which caused their movement patterns to be much less coordinated island-wide, leading to several spawning events,” Brendan explains.

A crab bridge helps crabs cross safely Parks Australia

What to Know Before Your Red Crab Adventure

Christmas Island draws an influx of tourists during the crab migration. While visitors can explore independently, accommodation options are limited. The island landscapes are characterized by rugged and steep terrain. Attractions are spread out, and without public transport, a car or e-bike is highly recommended to get around the island. Christmas Island is home to photographers who have a knack for immortalizing its beauty. Join one of their tours to learn how to take the best photos of this amazing place.

The best places to watch the migration are where the crabs cross roads, especially along Murray Road in Drumsite and Lily Beach Road. The best spots to watch the spawning are at the island’s beaches, like Flying Fish Cove, Ethel Beach, and Greta Beach.

Mitigate Climate Change to Protect Crab

Like many other places, Christmas Island is not immune to climate change-related challenges. In the years to come, the seasonality of the wet season may impact crab migration. Drier conditions could also increase the risk of wildfires.

Parks Australia is working to strengthen the island’s ecosystem and address the impacts of climate change through measures such as:

Suppress or eliminate super-colonies of yellow crazy ants. These ants pose a serious threat to red crabs, killing them when they stray into the colonies during their migration from the forest to the coast.
Cat eradication programs to protect flying foxes and forest birds, which play a key role in pollination and seed dispersal, helping the jungle regenerate more quickly.

Red crabs crossing please drive slowly. Credit Parks Australia

Crab Population is Vital to Ecosystem

A keystone species on Christmas Island, the health of the island ecosystem relies on a healthy red crab population.”Our main concern isn’t the overpopulation of red crabs, but the threats introduced to their health,” Brendan says. “Yellow crazy ants are the biggest threat to the red crab population, and Christmas Island National Park has been dealing with this threat for over 10 years.” In fact, effective crazy ant control has led to the red crab population to rebound to levels unseen since the 1980s.

The island remains a popular destination year-round, even outside the red crab migration season.

A Magical Island for Nature Lovers

For Brendan, his favorite places to explore include Dolly Beach, the Dales, Territory Day Park Lookout, and Flying Fish Cove. He also enjoys visiting the National Park that spans 63% of the entire island.

Visitors can join the guided tours of the Pink House to see two Extinct in the Wild reptiles—the blue-tailed skink and Lister’s gecko—and gain insights into efforts to bring them back from the brink of extinction.

No one locks doors on the island. Everyone leaves keys in their cars, and kids spend hours every day playing safely outdoors. The diverse community brings together a mix of Malay, Singaporean, Australian, and Chinese food and culture.

“I came here from Adelaide to take on a 12-month contract with Christmas Island National Park. Upon my arrival, I was completely awestruck by the island’s natural beauty and unique charm. I got married, started a family … and the rest is history!”