Strolling on the snow

Snow and more snow!

The deep snows this winter are too much for these little snowshoes we usually use here—one just postholes, and the enlarged feet have a hard time pulling up out of the hole. The old North Woods style of ‘shoe would be more suitable. But the little ‘shoes are what we have, so we tend to stick to the groomed trails, walking on the side of the trail as much as possible and avoiding disturbance of the classic tracks set by the groomer.

One day in late December, a friend and I strolled up Montana Creek, looking for signs of wildlife activity. But nary a track could be seen. Strange. Some distance up the trail, a bit of open water appeared, just a very narrow, intermittent channel. Friend wished for a dipper—and just on cue, one came around a curve, flitting downstream. It stopped briefly in each small opening in the ice but didn’t seem to find much to eat and eventually went farther downstream. But there wouldn’t be any open water there until it reached the Mendenhall River, so its explorations would have to continue. When streams are frozen, dippers often forage in intertidal zones.

The next week, we rambled around the Lower Loop at Eaglecrest, where critter-tracking is often rewarding. This day was no exception: there were weasel and porcupine trackways ranging widely; voles and shrews had scampered in and out of sheltered spots. Snowshoe hares had explored many places, usually under brush or low-hanging conifer branches, where the snow was not so deep.

There was not much sign of squirrel activity, just a few tramplings near some trees. I wonder if they were using tunnel systems under the deep snow—the squirrel that lives near my house seems to have long, well-used tunnels, which it often uses instead of traveling on the surface, popping up near what used to be a garden. I know that voles and shrews often scurry about below the snow, but they had appeared on the surface fairly commonly. So why not the squirrels– perhaps they weresnacking on things in their snow-buried middens??

Ptarmigan or grouse left their bipedal trackways, often in and around brushy thickets; they may have nibbled blueberry buds as they walked. One of these birds came up to a steep little bank on the edge of the trail and slid on its bum down the loose snow, to find its feet again at the bottom of the short slope.

I spent quite a lot of time in a spot where tracks were overlapping and complicated to sort out. Some were from hares, some from ptarmigan/grouse, but there were others also. Only a few of these others were clear enough to allow possible ID: maybe about an inch and a half wide, with five toes, one of them set back a little from the others.  Hmmm, quite possibly a marten! There was, however, no evidence of predation, so I can’t finish the story.

One critter that commonly leaves tracks near the Loop was missing from the records in the snow on this day: Deer tracks were conspicuous for their absence.

I was interested to see that the lower-most extension of the Loop, near the opening of the Treadwell Ditch trail, showed almost no sign of wildlife activity (just one vole track). I’d noticed this lack on other excursions up there. I have to wonder why so little activity is recorded there—the habitat is the same (to human eyes), so why is this part of the Loop apparently so un-used?

In early January, we walked up the Dan Moller trail, using the convenient snow-machine route, which was packed enough to walk without ‘shoes. Up through the meadows, looking for critter signs, but with little luck. The deep snow transformed the once-familiar landscape into unrecognizable terrain. A little imagination added to the fun; the heavy snows had laden the trees and stumps into wonderful shapes. One that caught my eye immediately was clearly an old woman, draped in her shawl, stooped over while mourning a dead companion at her feet.  Another was a small spruce whose top bore such a load of well-packed snow that it was bent into a full-curl ram’s horn. 

There’s no end to what you might find, if you go stravaiging around on our trails!

Snowy blankets

life in the subnivean world

Snow makes a great blanket (albeit damp and cool), insulating whatever lies below it from cold air above. As we found out not long ago, a few inches of snow kept solid (walkable) ice from forming on ponds, even after many days of single-digit temperatures.

Lots of critters make use of the snow. Ravens roll and toboggan; otters slide. Red squirrels often make winter nests in and under their snow-covered middens. Marten, the most arboreal of the weasel family, find winter resting places under the snow. They often use places where fallen branches and stumps intercept snowfall, creating spaces for resting as well as easier access to subnivean prey. They are reported to rest frequently in red squirrel middens, including those occupied by squirrels. Even birds find shelter under snowy blankets. Ptarmigan make burrows for night-time shelter, leaving little piles of fecal pellets in depressions, which we find in spring as the snow melts from the top of the burrow. Redpolls cluster together in tunnels under the snow to keep warm.

A lot goes on underneath the snows. Invertebrates of many kinds live in subnivean places. There are springtails, beetles and other insects, and spiders, some of them dormant, some of them active at least periodically. They are prey for shrews (which have to eat every few hours) and mice.

Keen’s mouse (the coastal form of the deer mouse) makes snow-blanketed nests in crevices or shallow burrows or cavities in logs and stumps. They often have short periods of torpor, to conserve energy, and make small caches of seeds. Unlike voles, they commonly come above the snow when foraging.

Voles and shrews scuttle along their tunnels, sometimes pursued by voracious weasels (ermine in much of Alaska and least weasel in the interior) that fit easily into those tunnels. Their nests are typically balls of vegetation with a cozy cavity, occasionally appropriated by a weasel that consumed the nest-maker. Meadow voles may even breed in winter if the snow blanket is thick and the food supply is good, but their mortality can be extremely high if the snow cover thins or their nests get wet. Many kinds of voles make winter food caches of roots and seeds and shrews often store prey for later eating.

Lemmings stay active all winter. Brown lemmings harvest the bases of grasses and sedges, as well as a lot of moss (an unusual food, not very digestible). Winter nests under the snow are thick-walled and often lined with their molted fur. The northern collared lemming makes long snow tunnels on the tundra in winter; snow burrows have nest chambers and separate latrines. The winter diet includes lots of low-growing willow bark and buds, reachable under the snow. They may even breed in winter, if the snow cover is really deep. The widespread northern bog lemming is the only lemming in Southeast, living in sphagnum bogs and other habitats. It makes nests and burrows under the snow, but little is known about its ecology.

Pikas are small relatives of hares that customarily live on rocky mountain slopes with nearby meadows. There are two species in North America, one in the Rockies and Cascades, and the collared pika in Interior Alaska and Yukon. All summer long they industriously gather grasses and herbs from the meadows to make hay piles in the rocky talus slopes; each pika may collect over twenty kilos of hay, making many trips per hour. Each pika defends a territory from other pikas and thus protects its haystacks. Most of the winter is spent under the snow, in burrows and crevices, living off the stored hay. Pikas are well adapted to cold but are very sensitive to heat; on hot summer days they hide in the rocks. Warming climate is a serious threat to their populations. In the southern Yukon, average temperatures have risen about two degrees C per decade since the 1960s, and the warming trend has already reduced pika numbers in some areas by ninety percent. There is no place for them to go: they can’t just move higher on the mountains since they are already there, and they can’t cross the warm valleys between the mountains.

Loss of snow cover is just one of the many well-documented deleterious effects of human-generated climate warming.

Winter to spring

diverse sightings in a cruel (?) month

A poet wrote “If winter comes, can spring be far behind?” For Juneau in 2013, the answer is Yes! We’ve had, I think, three big snowstorms in April. Another poet wrote: “April is the cruelest month…” and, this year (so far!), that seems appropriate (with apologies to said poets for taking their lines quite out of context! Also to my long-gone eleventh-grade English teacher, who would be rolling her eyes and shaking her head, because the lines floated into my head, out of context, but not the poets; I had to look ‘em up to refresh my so-called memory. Sorry, Miss Dahl!).

The snow seems likely to bring temporary hardship to many creatures. The nesting hummingbird is sitting tight but no doubt having a hard time finding enough food for herself. The ducks on my pond are swimming through thick slush. Juncos, which typically forage on the ground, are driven to visit the seed feeders hanging over the pond; they cling with some difficulty to perches made for smaller birds. Mountain goats may stay at low elevations longer than usual, because the snow is too deep in their alpine haunts, and any newborn kids become more vulnerable to bear predation than they would be in the alpine zone. Will the early blueberry flowers get pollinated if the bumblebees are obliged to retreat to their nests?

But beautiful it is; as the annual Audubon cruise to Berners Bay set out in a snowstorm, we told ourselves that there is no place more beautiful than Juneau.

The spring run of eulachon (hooligan) in the rivers of Berners Bay had not yet begun, and there were no signs of herring spawning. But there were obviously forage fish in the bay, because their marine predators were busy. Tightly packed squads of Steller sea lions splashed and dove in unison, chasing some kind of small fish, or rafted up to rest in between foraging forays. A rocky reef was lined with bald eagles, with harbor seals scattered around just offshore. We saw humpback whales doing something that most of us had not seen before: five or six whales were foraging together, shoulder to shoulder in a tight bunch, often making short dives simultaneously. Some lone humpbacks foraging elsewhere in the bay came and joined in. My guess is that there were several small schools of forage fish in the bay, as a preamble to the big spawning events, and the predators concentrated their efforts because the prey had a patchy distribution.

Along with the usual assortment of gulls and sea ducks, we saw yellow-billed loons, which commonly winter along the shores of the northeastern Pacific. They look a lot like common loons and are indeed closely related, but they have a pale, slightly up-tilted, bill. These birds would be staging for a northward migration to the Arctic tundra where they nest, probably about the middle of June. They have to wait for the tundra lakes to thaw, so they can hunt for fish and various invertebrates; if they go north before leads open in the ice, many would die. Breeding pairs get together on the nesting grounds, and each female commonly lays two eggs that hatch around midJuly. It takes about three years for the young birds to mature and find their own mates.

yellow-billed-loon-winter-plumage-by-bob-armstrong
Yellow-billed loon, winter plumage. Photo by Bob Armstrong

There are reportedly fewer than about three thousand of these loons in Alaska. Their populations may be limited by the availability of suitable habitat—they need lakes with early ice-out, protected shorelines for nest sites, stable water levels so the nests don’t get flooded, and clear, shallow waters for foraging. They also may have to compete with other loons for suitable habitat.

Another wintry foray in April took us on snowshoes up the forested route to Cropley Lake. Among the interesting observations was a well-gnawed tree where a porcupine had found dinner. Much of the bark was gone. Porcupines feed on the inner bark and commonly reject the tough outer bark. The unusual thing was a deep, very tidy, circular mat of outer-bark chips closely packed at the base of the tree. We’ve seen lots of porcupine-chewed tree but had never seen (or ?noticed) how the chips piled up so neatly. We also found a little hemlock tree that had contorted itself into a full circle in its struggle to reach the light. Never give up!

Out and about

bits and pieces from December

I try to get out for a walk every day, whatever the weather, although the weather may determine the length and location of the outing. How much I see of natural history interest varies greatly, depending on many factors, including a perceived need to watch the footing in sloppy mud or on slippery ice or wet rocks, sometimes a wish to be a bit sociable, or even do some serious (or not-so-serious) thinking. But most of the time, I like to keep my eyes and ears open to what is around me. So here are some bits and pieces from December.

As a cold snap settled in, Mendenhall Lake grumbled and growled and muttered in a long-winded soliloquy—the ice, talking to itself as the water froze and expanded. Smaller ponds were less loquacious but still murmured and popped at a lower decibel level. Meanwhile, overhead, large flocks of pine siskins flitted from spruce to spruce, sometimes swooping high over the canopy before disappearing in the crown of another cone-laden spruce.

In between short periods of deep cold, however, we had spells of surprisingly warm temperatures, turning our little bit of snow to slush and sending meltwater down over the existing ice on streams and ponds. Open water formed at inlets and outlets of ponds and along the fringes of Mendenhall Lake. A reliable observer reported seeing a beaver swimming in Mendenhall River in late December, when local beavers are normally snug in their lodges, sleeping or nibbling from their winter cache of twigs. That beaver was not the only one escaping cabin fever: in several locations, I saw very recent tree-cutting and branch-gnawing that had not been there a few days earlier.

On the ground near Moose Lake I found several small wind-broken cottonwood branches, with the upper sides nicely de-barked. Some lucky gnawer had capitalized on this bonanza. But who was it? Not a beaver, although beavers had debarked a cottonwood tree trunk near the lake, leaving the marks of wide incisor teeth. Not a porcupine—the tooth marks were too small. But the marks were too big for a mouse. My best guess was probably a snowshoe hare; hares are generally fairly numerous in the area and the incisor marks were similar in size to the teeth in a hare skull in my collection.

porcupine-midden-pam
Photo by Pam Bergeson

Along the Treadwell Ditch are many trees, usually hemlocks, that show the marks of porcupine gnawing—tooth-marked, barkless patches, low on the trunk. This is a common sight around here, of course. I was particularly interested to find at least two trees that seemed to have been completely girdled sometime in the past. The bark had been removed all the way around the tree, which would interrupt the flow of water and nutrients between roots and crown, starving the roots of food and the crown of water. Yet these trees sported full crowns of needles and looked healthy. How could that be? The porcupines had removed all the outer bark and eaten most of the nutritious inner bark, but a meager, sketchy, brown network of inner bark was still visible. Could it be that enough strands of inner bark remained to connect the roots and the crowns? Hard to believe that would be enough to support a good-sized tree!

There are other little mysteries about porcupines and hemlocks. Some trees have obviously been visited repeatedly, in different years. Old chewings have partially healed, but new ones are there too. Are these trees particularly tasty? Also, I get an impression (untested, so far) that porcupine gnawing is more common on the uphill side of a hemlock trunk. Is that really so, and if so, why?

A special pleasure was seeing two humpback whales spouting as they cruised near Lena Point. They may have been late-departers for winter in Hawaii or they may have been among the few that overwinter here, feeding on herring (and any other luckless little forage fishes). Not on this day, but sometimes one can see a few sea lions swimming near the corners of a foraging whale’s mouth, trying to catch the fish that slipped away from the whale. The herring equivalent of ‘out of the frying pan, into the fire’!