Can snowshoe hares outrace climate change?

Winner of National Association of Science Writers' 2013 Science in Society Award!

  • A snowshoe hare, in its white winter coat and tracking collar, is well camouflaged on a snowy January day near Seeley Lake, Montana.

    Colin Ruggiero
  • Snowshoeing in to the monitoring site

    Crolin Ruggiero
  • Weighing a hare

    Colin Ruggiero
  • Checking an ear tag

    Colin Ruggiero
  • With the help of UM graduate Sean Sultaire, Mills breaks down traps after a day in the field.

    Colin Ruggiero
  • Recording data that will help evaluate how hares are dealing with changing snow cover.

    Colin Ruggiero
  • Scott Mills snowmobiles in and out of the most remote areas of the Seeley-Swan Valley, where he traps snowshoe hares.

    Colin Ruggiero

Behind the wheel of his boxy red Ford F-250 truck -- complete with crimson-carpeted dashboard -- L. Scott Mills sipped his watery coffee and headed east. It was 18 degrees outside on a dim Missoula morning, a few days before the end of daylight-saving time. As the sun rose and the sky turned white, Mills followed Montana Route 200 along the lazy Blackfoot River, northeast toward the town of Seeley Lake. Bright yellow larches blazed among the pines, and a dusting of snow from a few days earlier still clung to the hillsides.

Just past Seeley Lake, Mills, a conservation biologist at the University of Montana, turned into the forest on an old logging road and parked behind his field assistants' blue pickup. Tucker Seitz and Sean Sultaire, two recent UM graduates, were readying antennas and receivers, beginning their daily task of tracking some of the 30-odd radio-collared hares hopping around the Seeley-Swan Valley this winter. We zipped our jackets, donned blaze-orange vests -- hunting season had just begun -- and tromped into the woods.

We ducked around lodgepole pines and Douglas firs, traipsing across bear grass and fallen spruce logs on terrain speckled with a light cover of snow. Seitz and Sultaire held their antennas in front of them, turning the metal rods to catch the signal. They listened to the steady beeps on receivers they'd hung from their necks. After about 15 minutes, they closed in on the hare, narrowing its location to an area of about 50 square feet. Then they spotted it.

Under a downed lodgepole, its upper branches and needles intact and forming a curtain of green and brown, the snowshoe hare sat nearly motionless, its lanky ears towering upright above its head. It crouched in a small hollow -- a "form," in hare-tracker parlance -- that it had made in the dirt. It took me a few moments to locate the hare, even with Mills' help. All that gave it away, finally, was the black of its eye framed by light fur.

Mills is trying to understand a biological phenomenon crucial to animal survival: seasonal camouflage. What drives the periodic coat color changes of animals like snowshoe hares, and is it something the animals can adjust? These questions, mused upon for centuries yet never fully studied, have lately taken on extra significance.

Like dozens of species that live in temperate climates around the globe, snowshoe hares grow new coats twice a year to blend in with the landscape. As climate change alters these landscapes -- and places that once were snowy white become increasingly brown -- the animals' future will likely depend in part on whether their camouflage can adapt in response.

Evolution is not just about one species ever-so-slowly transforming into another. It's also about much smaller, much faster changes that can determine whether a species will endure or perish as its world shifts. Aided in part by fast, relatively inexpensive DNA analysis, scientists are tracking these changes, and using them to help predict the future of species. They're probing fish that live in polluted waters for clues to how they tolerate toxins, and sequencing the genes of invasive plants to learn -- based on the plants' family trees -- which pose the biggest threats to native species.

To make effective conservation decisions in the age of climate change -- what to save, how to save it -- we need to understand how species adapt and change, and how past and future evolution affects their odds of survival.

Every week, Mills' team locates each collared hare and records the color of its coat -- what percentage white or brown -- and the amount of snow-covered ground in its immediate surroundings. Hoping for a good look at this particular male hare, Seitz squatted about four feet away from its hiding place and snapped a photo, then moved in closer and clicked again. As Seitz edged forward, the hare hopped from its hideout and covered a few dozen yards of forest before pausing. Out in the open, we could see its fur clearly. Its body was mostly brown, though flecked with white, and its face was predominantly white from its nose up to its eyes.
As winter looms, all the hares in this Montana forest begin to turn white within a week of one another, regardless of snow conditions or temperature, triggered by the disappearing sun. But once it starts, each hare's transformation -- which can take up to two months to complete -- is unique. Some hares turn white on their faces first, with their new fur spreading from nose to rump; others metamorphose in reverse. Some hares turn mostly white early on, keeping just a bit of brown for several weeks; others try on a tiny sample of white coat, as if waiting a while before committing to the whole outfit.

Beyond the initial sunlight trigger, though, what controls this seasonal cycle remains a puzzle. Can this particular hare adjust its internal rhythms? Will its descendants acquire a gene that helps match their fur to their habitat?

Because hiding, even in plain sight, is the snowshoe hare's ticket to survival, you might never see one while you're out walking in the woods. Yet the species is currently doing fine in Montana, and elsewhere across North America. That's good news for these ecosystems' meat eaters -- coyotes, wolves, bobcats, martens, hawks -- all of which have a taste for hare. Thanks to the carnivores, a hare's average life span in the wild is just a year. Nearly all of them meet the same end; it's only a matter of time.

While this state of affairs is unfortunate from the hare's perspective, it helps keep the rest of the ecosystem humming along just fine -- especially because hares breed like, well, rabbits. But like so much in nature, it's a fragile balance. If hares become too easy to catch, their populations are likely to crash -- and perhaps take down the predators that depend on them.

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