A study published in the journal Scientific Reports last month found that roads significantly changed some of the western Arctic caribou herd's behavior and delayed their migrations. The herd has one of the largest land migrations on the planet.
Tim Fullman, a senior ecologist with the Wilderness Society and one of the authors of the study, said caribou showed altered movements near roads throughout the year. Over 60% of collared caribou that encountered a road changed their route, according to the study.
"Those caribou with the altered movements ended up spending longer near roads than those with unaltered movements," Fullman said. "It's about three to three-and-a-half times longer on average."
Fullman said some caribou bounced away from roads, moved back and forth without crossing, or traced along the roads. On average, the study found caribou that came in contact with roads were delayed nine days from their normal migrations.
The western Arctic herd was once the largest in Alaska, and an individual caribou in the herd might travel over 3,000 miles each year. But over the last two decades, the herd has declined nearly 70% — from half a million caribou to an estimated 152,000 animals in 2023.
Fullman said that dramatic decline means it's become much more important to study factors affecting the herd, like the impact of roads.
"People care about caribou," said Fullman. "We rely on them for food. We rely on them for the important roles they play in the environment. Especially for Alaska Native people, the connections include cultural and spiritual relationships with caribou."
Fullman's study looked at decades of data from collared caribou and their reactions to five roads within the herd's range across Northwest Alaska – the Nome Road, the Dalton Highway, the Kivalina Evacuation Road, the Dahl Creek Airstrip, and the Delong Mountain Transportation System, commonly called the Red Dog Road.
The study used a method called Barrier Behavior Analysis that was developed in 2021 to study pronghorn and deer in the Lower 48. Fullman said this is the first time the method has been used to study caribou.
The study was a collaboration between the Alaska Department of Fish and Game, the National Park Service and the Wilderness Society. It builds off previous research from 2016 that found some caribou were delayed by over a month during their fall migrations after encountering the road that connects the Red Dog Mine to its port.
"We know that more decisions are going to be made, both about how to manage existing roads as well as about whether new roads should be built," Fullman said. "The hope is that our findings about how caribou respond to roads, the kinds of behaviors they show, will help to inform and support those kinds of decisions."
Fullman said the studies show the importance for more research on the herd and their behavior.
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