Snowy tracks

stories written on the winter landscape

Snowshoes crunched over deep snow. The sky was cerulean blue and the sun gradually crept around the mountain peaks. These were fine days to be out, seeing what we could see. We were especially interested in the tracks left by the wild critters as they went about their daily lives.

–A shrew left a long line of tiny marks by the side of a beaver pond. Short digressions led to tufts of grass or a buried stick, where spiders and bugs, slowed by the cold temperatures, might be found. Shrews only weigh a few grams and have a very high metabolic rate, so they have to eat almost continually. We often see their trails running over the snow and plunging into miniscule holes that lead under the snow blanket where prey might be found.

–Mouse trails are much less common. But one day we found a line of hopping prints that went out of the forest and across the upper intertidal zone to the most recent wrack line. The piles of tumbled rockweed might harbor small crustaceans, wayward seeds, or lost insects—all suitable for a snack. Another line of tracks went straight back into the shelter of the forest.

–Snowshoe hares had been busy in some areas. They too were looking for food, maybe willow or blueberry buds. But occasionally there were heavily trampled spots, very localized, as if there had been a dance or other social encounter. Popular routes became hare highways, packed flat along a small ridge or between two dense spruce stands.

–An otter had cruised for hundreds of yards along a frozen slough, making side excursions to visit (briefly) several beaver lodges. The deep trough left by its passage seldom came out in the open but usually stayed under the fringing conifers. Reaching the shore of a well-frozen lake, the otter abruptly turned around and went back the way it had come. The only open water on its route was a very small runnel below a beaver dam—a place not likely to hold good otter food.

–Across some thin pond ice, a great blue heron had gingerly minced its way from one patch of open water, at the inlet, to another, at the outlet. Taking very short strides on its long thin toes, it seemed to have been treading carefully. Little sticklebacks and juvenile coho, beware.

–In several places, we spotted narrow grooves on the snow surface, where a slim body had propelled itself on small feet. These wandering trails led to grassy tussocks, dove under logs, circled a pile of branches, disappeared under the snow and came out again. A mighty hunter was at work: a short-tailed weasel or ermine, whose coat turns white in winter, except for the tip of the tail. The short-legged, long body of a weasel is well-adapted for diving down vole tunnels and other tight places. However, that body form means that a weasel can’t afford to put on heavy layers of fat; the belly would drag when the weasel tried to run—not good for a hunter that has to keep moving for much of the day in search of prey. In addition to their small size, the body shape of weasels gives them a lot of surface area (where heat is lost) compared to the body volume (muscles and organs that generate heat), so they have a high metabolic rate to keep themselves warm. And that means they have to eat a lot. They eat mice and voles and small birds, and carrion when it’s available.

–Porcupines seem to wander widely, and we’ve found their trails in many places, often still distinguishable under a layer of new snow. One day we found a very fresh trail of footprints and even some quill-drag; we followed it along a little dirt bank until it disappeared over the edge. Looking down, we saw that a small log, sticking out parallel to the bank, had been wiped clean of new snow by the animal’s passage; the trail ended near the end of the log. Of course, we went around to an easier place to climb down the bank and investigated the trail’s end. There we found a deep burrow, with hairs and a few dried-up fecal pellets and a good barn-y smell, that ran into the bank for over two yards: a snug, dry den that had been used repeatedly for some time. Upon close inspection, that little access log had thousands of scratches, evidence of many balancing acts as the porcupine had ventured out and back.

Walking Gustavus beaches

predator leavings, big snails, and boring clams

A recent walk with two friends on some of the great sandy beaches of Gustavus provided several observations of interest. The four-footed friend probably had the advantage of us mere humans, because she could sniff many messages that were beyond our ken. Nevertheless, the curious-naturalist humans found much to see and discuss.

A line of wolf tracks followed the upper edge of the sand, steadily headed…somewhere. One huge wolf scat held remains of a murre, probably scavenged from a carcass, and another was made up mostly of clay, with a few feathers. Do wolves self-medicate with clay, as some birds do (to counter toxins in their food)?

There was evidence that predatory birds had feasted on murres, mallards, and a loon. Owls and eagles undoubtedly accounted for some of these avian remains. But also, perched on a log within distant binocular range was a slim, gray bird that we thought might be a peregrine falcon. Some owl pellets held the bones of voles, including skulls with teeth, which made identification of the prey relatively easy. A set of vole molars looks, on the grinding surface, like a row of tightly packed triangles; this is quite different from the cusped molars of deer mice, for example. Perhaps I needn’t have bothered to look closely, though: I was interested to learn, from a well-known naturalist in Gustavus, that deer mice are scarce over there, for reasons undetermined.

Scattered along the sand were several strongly ridged, giant snail shells, the biggest whelks I’ve ever seen. These specimens were four or five inches long, but they are said to reach a length of seven inches or so. They belong to the genus Neptunea, but the species name is still undetermined, thanks to some taxonomic confusions. They hang out in the sediments but emerge to travel, feed, and lay their eggs. Neptuneas make their living by drilling (with their file-like radulas) into the shells of other molluscs and slurping out the contents, eating polychaete worms, and by scavenging dead and dying critters. Females produce masses of egg capsules that are spread over rocks and in rocky crevices. Each capsule contains about two thousand eggs, but many of these are not fated to become juvenile snails, because they are eaten by their siblings. After developing inside the protective capsule for many months, well-fed young snails emerge.

Clam shells were everywhere, mostly horse clams. But on one beach we found deeply arched clam shells, each with a pronounced internal projection, for muscle attachment, near the hinge. This beast was entirely new to me, so my learning curve took a jump. These clams are called piddocks (Zirfaea pilsbryi). Piddocks and some other bivalve molluscs burrow into the substrate using their shell as augers; piddocks make their tunnels in clay, sand, or even rock (!). The sharp, jagged teeth on the front part of the shell slowly rasps away, back and forth, as the piddock rotates, eventually making a full circle, only to start over on the next round. Their tunnels can be over a foot long, so their siphons (or the so-called neck: the paired tubes, one of which is used for breathing and drawing in food particles, and the other for excreting wastes) are substantial. If the piddock is eating well and grows as it slowly burrows, the first part of the tunnel becomes too small for the clam to back out, and it can only go forward.

piddock-kmh
Piddock (Zirfaea pilsbryi). Photo by K. Hocker

I am not a marine biologist of any sort, but I love finding out more about this unfamiliar world.