“Empty,” called Claire Montgomerie over her shoulder with a hint of relief in her voice. Matt Kynoch and I paused in our crashing through the brush, waited for Claire to make sure the live trap was still properly set, and then we all tromped back along the transect together. “Full,” announced Matt as we approached the next trap, a snowshoe hare cowering inside.
Matt and Claire—both graduate students at the University of Alaska Fairbanks—sprang to action with practiced efficiency. Claire fit a long, white pillowcase around one end of the trap, grasped the door through the fabric, and opened it wide. Matt crouched at the far end and blew little puffs of air on the hare’s rear end to encourage it to run into the bag. Sometimes, cartoon-like, the hare would blast into the bag with such force that you could see the impression of its little face through the fabric.
For three days in the summer of 2018 we worked on this mark-recapture survey along a pipeline access road in the Brooks Range of northern Alaska, gathering data that would help scientists at the nearby Gates of the Arctic National Park estimate hare population numbers for this year. Our opinion? The population is high. Almost every trap was full, which meant a delayed lunch, and that sense of relief to find an empty trap.
Along one rutted gravel road we set 14 live traps baited with alfalfa cubes and carrots. Claire pointed out exposed dirt on the road cuts where hares have been recorded coming to lick the soil. National Park Service scientist Donna DiFolco had asked us to help recapture hares who had been previously deployed with GPS collars to track their use of the mineral licks.
Later in the week we collected data for Claire’s master’s thesis. From each hare, they plucked fluffy tufts of hair, clipped a toenail, and drew blood from a vein in the hind leg. I also helped collect fresh bunny scat into little plastic bags. Once back in the lab, Claire would run tests on the materials to find signs of the hare’s stress levels and other measures of health. All of this was in the name of science, and Claire is not the first to try and tease out mechanisms behind a roughly 10-year cycle of snowshoe hare population highs and lows.
The classic, top-down, predator-driven theory posits that as hares increase, the number of lynx who feed on them go up, too. Hares get eaten. Lynx have more babies. Soon there are too many lynx and not enough hares to feed them all. The lynx population goes down, hare numbers recover. The cycle starts over. Most scientists now believe that this is oversimplified.
For example, predators don’t just kill hares by eating them. When lynx numbers are high, hares may spend more time being vigilant and less time feeding. Plus, DeAngelis et al, 2015, found that when numerous hares browse heavily on their favorite winter foods, those willow and birch shrubs increase the concentration of anti-herbivory chemicals in their tender new twigs.
Therefore, at the same point in the cycle when hares experience the most stress from high numbers of predators, they are left eating woodier and more toxic twigs. That leads to lower survival and reproduction—except for those hares who were coming to lick the soil.
When I tell people about my 2018 sabbatical to Alaska, this snowshoe hare study is always a highlight. Which is why I was so excited to see a recent headline from the National Park Service during my lunch hour last week. After decades of research, Donna DiFolco, the NPS scientist who Claire was assisting with the mineral lick study, confirmed what locals had already observed: in areas with mineral licks, the hare population grows larger for longer. Instead of peaking equally every 10 years, the hares with access to natural mineral licks have a super peak every 20 years, and a smaller one in between.
By comparing the samples of hare scat—some of which I helped collect!—Donna was able to determine that mineral licks were providing critical nutrients like sodium, calcium, potassium, and magnesium that helped the hares to stay healthy even when the plants they ate became more toxic. Donna retired last year, but her colleagues will continue to investigate the importance of mineral licks for other mammals, too.
All those years ago, while Clarie, Matt and I were staving off hanger to trap all the hares, I commented to them that 2018 was surely a peak year. Like good scientists, they equivocated. That could only be determined in hindsight. Well, according to Donna’s data, the super peak was still one year away—in 2019. If I’d have been part of the research team that year, I might have had to join the hares in eating dirt!
Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.
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Last Update: Apr 09, 2025 7:32 am CDT
