Game Range Ramblin's
Game Range Articles
by Mike Thompson,
FW&P wildlife biologist,
writing for the Pathfinder
March 8, 2001
Seeley Swan Pathfinder
Seeley Lake, Montana
by Mike Thompson
I heard a lot about wildlife in the Blackfoot and Clearwater valleys at the annual meeting of the Montana Chapter of The Wildlife Society last week in Butte.
Some of the most interesting information pertained to studies of lynx and their primary prey, the snowshoe hare, in the Seeley Lake area. And, I learned a new word.
On the surface, it sounds like something you feel when you read this column each week.
But, actually, tortuosity is a term used by scientists to describe the path an animal takes when traveling between two points. The more an animal deviates from a straight-line path, wandering about to smell the roses, the higher its tortuosity. A straight line path exhibits zero tortuosity.
Julie Fuller, a senior wildlife student at the University of Montana, described how she measured tortuosity in our snowshoe hares over the past two winters to evaluate habitat quality around Seeley Lake.
Her idea was simple. If hares don't really like a habitat, they should move quickly through in a straight line, without much tortuosity. On the other hand, if they like a habitat, they should meander more, exhibiting more tortuosity.
To locate a starting point for each day in the field, she followed radio signals emitted by instrumented hares, and then backtracked about 70 meters. She counted numbers of tracks (to gauge the relative speed of travel) and changes in direction at 5-meter intervals. She also noted the corresponding habitat category.
In addition to studying the travels of hares that were undisturbed by the research, Julie also conducted a simulated predation experiment. For this purpose, she would flush a hare with a leashed dog, then back away. One hour later, she relocated the flushed hare by following the radio signal and then backtracked and collected data as usual.
As expected, hares that were flushed by the leashed dog exhibited low tortuosity in response. They just boogied straight away from the predator.
What was more interesting was that hares in young, open, conifer stands exhibited much the same travel patterns as hares that were flushed by the dog. These stands were old clearcuts where the regenerating seedlings and saplings had been thinned. According to Julie's data, hares in these habitats were just passing through.
On the other hand, tortuosity was highest in old, dense, conifer stands. Numbers of tracks per meter also indicated that hares wandered more slowly through these older, more heavily timbered forests than in young, open stands. It would seem there were more things for hares to do in older, denser stands than in stands where a good proportion of the cover was removed.
Generally, what's good for hares is good for lynx. Hares are the primary food source for lynx in winter. So, habitats selected by hares are also important for lynx.
There is also a lot of work being done on the genetics of our lynx populations. Michael Schwartz, from the University of Montana, conducted genetics research to test whether populations at the southern end of the geographic range of lynx in North America are isolated from the core of the population in Canada. He sampled lynx DNA from Alaska to Seeley Lake, across a distance of some 2,000 miles.
Surprisingly, he found no genetic evidence to suggest that our lynx in the Seeley Lake area are isolated from the larger northern population. This leads scientists to assume that lynx in our area mix enough with lynx from further north to keep the overall population connected and genetically diverse. It's not that our lynx routinely migrate to the far north and back. More likely, it means that our local population benefits from periodic pulses of animals from Canada, which keeps the genes flowing across political boundaries.
According to Kevin McKelvey, of the Rocky Mountain Research Station in Missoula, we're about due for this decade's pulse of lynx from Canada. Evidence from fur trapping records in Canada and the United States indicate that Montana benefits from an influx of lynx at the early part of each decade, probably related to the 10-year cycle in hare abundance in Canada. When hares are at peak numbers, lynx numbers soon follow and lynx spread out over a larger area than they do at lows in the population cycle.
You needn't worry about being trampled by any stampede of lynx in the next year or so, but you might be rewarded for paying more attention to what flashes in your headlights these days.