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Migrations Part 1: Roadkill pegs critter movements

A herd of deer uses a wildlife underpass on Highway 21 east of Boise not long after it was constructed in spring 2011.
A herd of deer uses a wildlife underpass on Highway 21 east of Boise not long after it was constructed in spring 2011.

WILDLIFE WATCHING -- Migrations are the topic of this week's wildlife story series Idaho Fish and Game is presenting online during the department's 75th anniversary observance.

In Part 1 of the three-part post of "reminders" on migrations, the department notes that mammal movements can be tracked, in part, by roadkill.

And while there are plenty of carcasses to remind us that wildlife is moving along North Idaho roads, the Panhandle's toll doesn't rank close to the carnage found along highways in other portions of the state.  Here's the first part of the IFG migrations post to raise awareness about issues facing wildlife:


Mammals do it. Birds and fish do it. Even insects do it.

They migrate as part of their inborn strategy for survival, and the arrival of winter triggers a massive migration of all kinds of wildlife.

They may travel a thousand miles or a few feet. The distance is not what defines migration; it’s that animals move between habitats during the year to survive. They may move for many reasons – to find food, breed or raise their young. Migration is a tool they use when a habitat no longer meets their needs.

Migration patterns and routes are ancient and have been influenced by the natural features of the land, water and air. The same natural features that foster wildlife movement are also attractive to human activities. Roads bisect open spaces. Wind turbines pop up on ridgelines. Dams block rivers. Communication towers light up the night sky. Houses are built in key habitat. And human structures frequently become problems for migrating wildlife.


Wildlife and vehicle collisions are the most visible conflict between migrating wildlife and roads. More than 5,000 deer, elk and moose were killed by cars on Idaho’s roads in 2011.

Information is gathered through a Road Kill database. 

In known hotspots around Idaho up to 100 or more animals are killed crossing roads every year. Some of these include:

  • Interstate 15, between Pocatello and Inkom, cuts through a major deer migration corridor.
  • Highway 75 north of Salmon, where 55 bighorn sheep have been killed since 1986.
  • Highway 30, from east of Montpelier to Wyoming, where up to 6,000 deer and elk cross the road, has one of the worst wildlife road mortality rates in southeast Idaho.          
  • Highway 20 in the Island Park area is known for collisions with elk and moose.
  • Highway 95 from the Canadian border to just south of Coeur d’Alene where 900 animals, most of them white-tailed deer, were hit by cars in 2011.
  • Highway 21 northeast of Boise repeatedly crosses the primary migration route of up to 9,000 deer and elk in the Boise Mountains. Hundreds of deer and elk are hit every winter along this road.

Sometimes money, talent and motivation score a win for wildlife. Examples include the wildlife underpass on Highway 21 outside of Boise, another underpass recently built into Highway 95 just north of Coeur d’Alene, and wildlife fencing along Interstate 15 outside of Pocatello. 

Tomorrow, Part 2: Fish.

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Rich Landers
Rich Landers joined The Spokesman-Review in 1977. He is the Outdoors editor for the Sports Department writing and photographing stories about hiking, hunting, fishing, boating, conservation, nature and wildlife and related topics.

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