A Wintery Walk

a wonderful weasel encounter

Days are rapidly getting shorter, and the peanut butter junkies at my feeders are voracious. The familiar Oregon juncos that thronged the feeders all summer are now scarce. But I’ve begun to see slate-colored juncos, here from the Interior for the winter. Closely related to the Oregon types (both are usually classed as subspecies of dark-eyed junco), but the new arrivals took at least a week to figure out how to exploit the peanut butter feeder. Maybe they watched the chickadees and got the idea.

On a lovely, sunny but cool and windy, day in mid-October, a little group of friends strolled up the road at Eaglecrest to go off onto the upper ski loop. Darting in and out of the angular rocks that line the road toward the Black Bear lift was a small white critter that disappeared almost as soon as it showed its head. So it took us a little time to ascertain who it was: of course, a short-tailed weasel or ermine (called a stoat in Europe). It then gave us many chances to see it as it explored both sides of the road, around the turn and past the Kimball memorial bench, popping up its head every so often to look around (and perhaps to check on us). The weasel was presumably hunting for something edible, such as a vole or shrew, but we saw no evidence of success.

Photo by David Bergeson

The white winter fur was certainly conspicuous against a background of gray rocks and brown fern fronds. When there’s snow on the ground, of course it’s a different matter—the white fur is great camouflage then, only the black tail tip and a beady black eye marking the beast on a white background. “Our’ weasel apparently had turned its coat from summer brown to winter white well before snow would cover the ground (although a little dusting fell a few days later). Molt is said to be initiated by changes in photoperiod (day length), and modified by temperature, but southern ermine don’t change to white at all. In northern populations, the physiology of molting to winter color is not closely timed to reliable seasonal snow cover; in fact, on snow-free Haida Gwai’i, ermine still acquire a white winter coat. This leaves open a question about why molt is not better synchronized with background color everywhere.

Weasels are built long and slender, which enables them to slip into narrow tunnels, even into vole hideouts in pursuit of prey. However, that elongated body has a lot of surface area (where heat is lost) relative to body volume (where heat is generated), so weasels have a high metabolic rate that generates heat– but necessitates lots of food. An active hunting style presumably provides more encounters with prey (than a sit-and-wait style, for instance), but has its own energetic costs. They need to eat several times a day (taking in about thirty percent of their body weight!) and have a well-insulated nest (often stolen from a victim) in which to rest between hunts. If the usual prey of small rodents is scarce, weasels may hunt hares, squirrels, birds, and even eat worms and bugs and carrion if necessary. They cache dead prey for future meals.

Mating season is in spring, but fertilized eggs are not implanted in a female’s uterus until nine or ten months later. Then the embryos develop into babies in about a month, the newborns staying in the nest for a couple of months or so. Litter size is variable, usually four to eight kits, but well-fed females can produce much larger litters (up to eighteen kits!). Juvenile females become sexually mature while still in the natal nest and may (if a mature male was nearby) already carry fertilized eggs when they disperse to establish their own home ranges. Males can’t inseminate their female litter-mates because they don’t mature until about a year old.

Here are a few more interesting tidbits about weasels: They have excellent color vision, unlike most mammals. They climb well, with reversible ankle joints (like squirrels) so they can descend a tree head-first. If threatened by a superior predator, such as a cat, they may pretend to be dead; if not eaten, they quickly revive and run away.

At this time in October, there was a thin sheet of ice on my home pond in the morning and the ponds at Eaglecrest were ice-covered. Nevertheless, we saw caddisfly larvae in their cases, hanging out on the bottom of a few ponds or moving extremely slowly. They probably spend the winter as larvae, feeding on detritus when possible, but otherwise quiescent; pupation and metamorphosis into flying adults would occur the following year.

A few blueberries clung on their bushes, and I was informed that they were exceptionally tasty. The bright green fronds of deer fern and fern-leaf goldthread stood out on a background of brown, dead and dying vegetation. On the surface of some old skunk cabbage leaves, tiny pools of water had coalesced and frozen solid, forming jewel-like, nearly spherical beads that gleamed in the sunlight.

We ate our lunches in warm sunshine, all spread out in the lee of a grassy bank. The first wintery walk of the year turned out to be a good one.

New Year’s Day 2012

mustelids and lichens in the muskeg lands

Snow was falling, snow on snow, but—unlike the song—this midwinter day was not bleak at all. With two friends, one two-footed and one four-footed, I set out to explore the forest and small muskegs near the Auke Bay school. This was not our original destination, but we got part way out the road, watched a truck slither and spin out over both lanes in the unplowed slush, and decided we’d find a place closer to town. I’d never been in the area behind the school before, so everything was new to me.

No birds seemed to be active there, but we soon found the trail of a short-tailed weasel, also known as ermine, particularly in winter when the fur is white. It had popped out of a hole roughly the size of a fifty-cent piece, looped over the snow for a few feet, and then dived into the snow again. Both of these snow-holes led to open spaces under shrubs bent under the weight of snow, where mice or voles or shrews might provide a snack. The long, narrow bodies of the weasels allow them to follow their prey into small tunnels.

On the surface of the snow, we could easily see their footprints, with the rear feet landing where the front feet had been, as it took off in the next leap. Each leap covered about a foot of distance. They have such short legs that the fastest way to get around is bending the long, sinuous body to extend the stride.

Short-tailed weasels are ferocious predators, dining on mice and other small mammals by preference, but sometimes eating birds, insects, worms, and even young snowshoe hares. Males weigh up to about seven ounces, but females are considerably smaller. They have high metabolic rates and have to eat a lot every day; females with litters may kill four mice a day.

A bit farther on, we found the trail of a bigger relative of the weasel. This path led hither and yon through shrub thickets, briefly into a tiny rivulet, along a log, under some low-hanging hemlock branches, and into still more thickets. Although we occasionally lost the trail for a little way, we eventually followed it for several hundred yards. We decided the trail-maker was probably a pine marten, partly because the footprints seemed a bit too big and furry for a mink, and partly because no sensible, hungry mink should be so far from the delicacies along the shore.

Trudging through the brush can be easier in winter than in summer. Snow presses down many of the blueberry and menziesia branches, and the two humans on snowshoes could stomp over the bent branches. Our canine companion was less fortunate; her snowshoe-less feet sometimes plunged through the brush piles, to the full length of all four legs, leaving her to wallow her way out.

Even though our broad feet helped us through and over the bushes, we still emerged with our knit caps full of lichens and twigs. And every so often a snow-laden arch of branches would give way, depositing us unceremoniously into a hole. We think this is fun, apparently, because we keep doing it.

Along the way, we noticed an area with a spectacular display of beard lichen festooned on almost every branch. Some of the strands were easily over six feet long. We wondered how it is that there are localized ‘hot spots’ for this lichen. Environmental conditions for good growth, including light and lack of aerial pollutants, must be part of the explanation. But it seems likely that dispersal patterns also contribute to the patchiness of strong lichen colonies: Spores and fragments of lichens are carried on the wind, so the direction, speed, and timing of winds would probably deposit them in semi-predictable patterns. Here’s a complex research problem awaiting a clever young scientist.