Genetics Reveal Unique Caribou Species

Feb. 20, 2009 -- Looks can be deceiving when it comes to caribou in the Canadian Rockies.

Long considered members of one subspecies, many mountain caribou are closely related to a different subspecies that lives hundreds of miles to the north, according to the first detailed look at the genetics of these endangered animals.

The discovery suggests that the system of caribou classification needs serious reorganization -- and soon. Finding the best way to save the species depends on it.

"The challenges for these caribou are quite dire," said Byron Weckworth, a conservation geneticist at the University of Calgary. "We have to make some good policy and management decisions now and quickly before it's too late."

During the last glacial period, beginning about 100,000 years ago, ice sheets separated northern populations of caribou from southern ones, causing them to split into two main subspecies. Besides looking different, the two groups developed different lifestyles.

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Barren-ground caribou in the north, for example, live in densely packed groups, and they seasonally migrate hundreds of miles. Woodland caribou are more solitary and more sedentary.

Within each subspecies, caribou are also grouped into ecotypes, such as boreal or mountain. Adding to the confusion, different studies have used different criteria to categorize them. And different Canadian provinces use different terms.

Mountain caribou have become victims of this mish-mashed naming system. Technically, they belong to the woodland group. But some mountain caribou migrate like barren-ground caribou do -- spending summers in high alpine regions and their winters on lower slopes many miles away. Other mountain caribou are more settled, true to their woodland name.

With the help of radio collars, Weckworth and colleagues spent a decade tracking the movements of 223 members of this mountainous group. The researchers also studied the animals' DNA.

Their results showed that some of the mountain caribou were clearly descended from the barren-ground subspecies, with many of the same key genetic signatures. Those animals tended to migrate from season to season. Other individuals clearly belonged on the woodland family tree, and those tended to stay put.

Based on the known rate of DNA mutations, the scientists were able to conclude that the mixing happened about 10,000 years ago. Around that time, the climate grew warmer and corridors opened up in the ice, allowing barren-ground caribou and woodland caribou to reconnect. The variety in behavior among modern mountain caribou reflects that genetic history.