thoughts on a widespread local mustelid

Right after a little (belated) snowfall in early December, I chanced to be prowling around some ponds in the Mendenhall Glacier Rec Area. Mink feet had been there before me, leaving crisply defined footprints in the trails. That mink mostly kept to the foot paths rather than humping over and under the frozen grasses, but made occasional forays to the edges of the almost-frozen ponds. Mink –and deer, bear, and porcupines—often use ‘our’ trails, where there is easy going; snowshoe hares don’t seem to do so very often.

Mink can climb very well and have a rotatable ankle joint that lets them come down a tree headfirst (like a squirrel). But they usually hunt on the ground and in shallow water, both salt and fresh. They swim well, with partially webbed toes, and can dive several meters deep. Their fur is water-repellent. They live all over Alaska, except for some islands and the very far north, reaching high densities in Southeast (except where heavily trapped).

Photo by Bob Armstrong

Dens are usually near water—in hollow logs or burrows, under tree roots, often in an abandoned den of some other animal, such as a beaver or marmot. The video cam at the visitor center sometimes catches a mink exploring even the occupied beaver lodge in Steep Creek. Mink aren’t likely to use a burrow that belongs to an otter, however, because relationships between mink and otter are generally hostile. They share many of the same eating habits, and otters sometimes kill and eat mink.

Mink are opportunistic foragers for meat of all sorts—everything from bugs and earthworms to fish, small mammals, and birds. When foraging in the intertidal zone, they take crabs, clams, little fish, and snails. Mink also gobble up bird eggs and carrion, including salmon carcasses. Cannibalism sometimes occurs. A big male mink sometimes may take down a hare or muskrat or a sitting bird twice its own size.

Photo by Bob Armstrong

Mink are fierce enough to tackle prey that is bigger than themselves. Years ago, however, my old cat who was an experienced hunter, observed a mink travelling on the other side of my home pond and got wildly excited. She could hardly sit still at the window, bumping into the glass, whining, champing her teeth, twitching all over. Little did she know that she would become mink lunchmeat, had she been outdoors and free to engage with this so-attractive creature.

Mating, for mink, occurs in early spring and young are generally born in June. There may be as many as ten of them in a litter, but four or five would be more usual. Both male and female mate promiscuously, so litter mates may have different fathers. Mating often begins with a rough and no doubt boisterous fight that may leave the female with some wounds. The male then grabs the female by the back of the neck and they copulate, often several times. Copulation is a prolonged process, sometimes lasting as hour.

Eggs are fertilized over a period of several days but do not begin to develop immediately. Mink, along with other members of the weasel family, delay the implantation of the fertilized egg in the wall of the uterus. That egg may float around for several weeks before attaching to the uterine wall, getting a blood supply (via the placenta) from the mother, and starting to develop. From implantation to birth takes only about a month but, as a result of delayed implantation, there can be as many as three months between copulation and birthing.

Kits are born blind, deaf, thinly furred, and toothless. They get their milk teeth after about sixteen days, and their permanent teeth begin to erupt after about six weeks. Their eyes open at a little over three weeks and weaning occurs at about five weeks. Kits start hunting, along with the mother, at about eight weeks of age, but become independent after another month and disperse to find their own home ranges. They mature by the next spring and can breed then.

American mink were introduced to Europe decades ago and now occur across much of northern Eurasia. They compete with the smaller, native Eurasian mink, whose populations have declined dramatically from that competition and many other factors. Mink were also introduced, more recently, to southern South America, which previously lacked any similar predator—no doubt the expanding mink populations cause consternation and carnage among the native riparian and shoreline birds there.


Trailside observations

In sun and snow and sleet and hail…

Here’s an assortment of winter observations that gave pleasure to some trail-walkers.

–Late November, Eaglecrest. Parks and Rec hikers on snowshoes went up the road, but the majority decided to go home for lunch. Two of us went on, over toward Hilda meadows, and perched on a log for a snack. Too busy feeding our faces for a few minutes, we eventually began to notice what was around us. Right behind our comfortable log was a big spruce tree with two lumps at the very top. The upper lump was pretending to be a moss wad, while the lower one was eating spruce needles. Both young porcupines were very wet, but the lower one suddenly roused up and rapidly shook itself dry—moving faster than I’d ever seen a porcupine move. The upper one slept on.

–Late November, Mendenhall Lake beach. A small stream flowed over the beach, creating a little opening in the ice. Three eagles were bickering over the remnants of a salmon carcass, which was probably fairly fresh (judging from the bright red blood stains on the ice). We often see late-spawning coho in the streams that feed the upper Mendenhall (years ago, in December, I counted over a hundred eagles on the stretch of Dredge Creek below Thunder Mountain; they were there because the creek was full of coho). One of the eagles snatched up the tail piece and flew off, hotly pursued by a pirate that eventually won the tasty morsel.

–Mid December, Eaglecrest. Lovely soft snow covered the ground, so animal-tracking was really good. Shrews had been very busy, running over the snow from one bush to another. Lots of other mammals had been active, too: deer, weasel, hare, porcupine, red squirrel, and mouse. Sadly, we found no ptarmigan tracks at all.

–Mid December, Dredge Lakes area. After a deep freeze, a warm spell had melted ice cover and opened up some of the ponds, and beavers had become active. There were new cuttings in the woods, new twigs in the winter caches, and some of the perpetrators were repairing their dams. The Beaver Patrol was called out of its own winter torpor to make notches in a few dams, lowering water levels in certain ponds so that nearby trails were dry , permitting passage of any late-spawning coho, and allowing juvenile salmon to move up and down stream if they chose to do so.

Photo by Kerry Howard

–Late December, Mendenhall wetlands. ‘Twas a very uneventful walk in a blustery wind. But suddenly two small birds blew (not flew!) in and tumbled into the grass. Righting themselves, they revealed themselves as a pair of gray-crowned rosyfinches, a species I’ve seen in upper Glacier Bay and on Mt Roberts, but not out here. That turned the day into a ‘plus’.

–Late December, Dredge Lakes area. Very low temperatures had refrozen almost all the ponds and streams. However, the ditch from Moraine Lake to Crystal Lake had a couple of very small ice-free patches. And there we saw a dipper, bobbing in and out of those dark pools, no doubt very hungry.

Any sensible dipper would go downstream, perhaps to an estuary, where bugs and fish would be more available!

–Early January, Herbert River trail. A mink had coursed along the elevated riverbank, in and out of the brush, occasionally down to the water’s edge. A set of extremely large moose tracks crossed the trail. That long-striding giant was really moving—the foot prints were often five feet apart. The trackway led through brush and over the arching branches of a fallen tree—almost four feet above the ground. Those long legs! I would have loved to watch that beast (from a respectful distance)!

–Early January, Perseverance trail. Recent heavy rains had brought down some small landslides, not unexpectedly. Unlike the trails near the glacier, this one was nearly clear of ice, and walking was easy. There was fresh snow on the ground, up past Ebner Falls, showing up a few porcupine tracks and some very recent red squirrel trackways. A mouse had crossed the trail with big jumps, several times its body length, leaving clear footprints as it hustled into cover across the open trail. I like seeing mouse tracks, in part because I don’t see them very often.

–Mid January, Switzer Creek area. Before the predicted rains and rising temperatures wrecked the lovely fresh snow, we found tracks of deer, porcupine, possible coyote, and a few mysteries. A shrew had scuttled across the soft snow, making a narrow groove marked by its tiny feet. A good find was a trackway of a grouse, striding through the snow and under low-hanging bushes in the woods. This took a few minutes of searching to determine the track-maker, because the new snow was so soft that it often fell down into the tracks, obscuring the prints. But finally we found good marks of three avian toes.

Stories in the snow

a snowy ramble reveals winter action

I love to go a-wandering along a snowy trail, looking for signs left by others who’ve been out on their business of living. A recent prolonged cold spell had kept the snow soft, preserving evidence of a very busy wildlife community along a local creek.

Mink tracks rambled along the creek-side, dipping down to the stream and curving up into the forest. The footprints were bigger than those of a second mink that traveled part of the same route, so my naturalist friend and I guessed that the first mink was a male. His trackway led a long way upstream on one side of the creek and seemed to circle back down on the other side—at least the footprints were the same size there. This might have been a male patrolling his territory.

Everywhere, we found the delicate, stitchery trackways of small rodents. According to the books at hand, mice are likely to drag their long tails, flipping them to the side as a counter-balance during sharp turns, but voles don’t usually show tail-drag marks. If that’s right, we had both mice and voles, especially on one side of the creek. The tiny trackways of shrews were less numerous.

Snowshoe hares had been busy, especially on the other side of the creek. Trackways led up to the streambank, then away, then back to creekside, then away. It was as if the hares wanted to cross the fragile ice but, lacking the nerve to do so, just dithered along the bank.

A bird had hopped about extensively in and out of some brushy areas. The tracks seemed too small to be those of a junco. Then we found wing-prints where the bird had flitted a short distance to a new site, and the length of the wing was clearly too long to belong to a junco. My guess was possibly a varied thrush, some of which overwinter here.

The only actual bird we saw was a brown creeper, hitching its way up a tree trunk and flying down to go up the next tree—their typical foraging pattern as they search for tiny bugs in the bark. According to the literature, creepers commonly concentrate their efforts on trees with ridged bark, the deeper the ridges the better; this kind of bark harbors more insects than smoother bark.

A few deer tracks, both large and small, appeared as we walked along. But there was much less deer traffic here than, say, in Gastineau Meadows, where peripatetic deer had cruised all over the place.

My friend called to me: Come look at this! I saw a shallow groove in the snow on the streambank and, without thinking, said: Oh, a shrew trail. Look again, said my friend. Ah—there’s a faint yellow stain at the bottom of the groove. And here, where I had casually supposed my ’shrew’ had dived under the snow, was—not a burrow at all, but just a deep dimple. My friend, who is smarter than I am, said: I think a bird, maybe a kingfisher, perched on that branch near the edge of the stream and projectile-defecated a jet of hot poop, melting the groove in the snow. So we said: Well, if that’s so, then in the dimple at the end of groove there should be a little wad of solid waste. And yes, indeed there was! Good detective work, friend!

A final little treasure on this walk was a dead red alder that sported a beautiful array of conks (or shelf-fungi). The living conks all had a slightly soft pile of white stuff at their lower edges. This stuff had occasionally smeared sideways over the bark, showing that it had been soft when the temperatures were above freezing. What is this stuff?

Phellinus conks. Photo by Katherine Hocker

I took a sample to a local forest pathologist, who put it under his microscope. He said that the white material was certainly fungal mycelium (the technical word for the mass of filaments that grow through the wood before producing the spore-bearing conk). However, without DNA work, there’s no way to know if it belongs to a parasitic fungus growing on the conk or to the conk species itself, because this kind of conk (of the genus Phellinus) often grows some of its own filaments right down through the conk itself. So we ended our walk with one more mystery.

March madness…

…our way

Madness in March usually refers to a frenzy of college basketball, or maybe Gold Medal basketball in Juneau. But the madness of naturalist-explorers takes a different form.

Encouraged by some tantalizing comments from a Friendly Observer, a friend and I went back to the Dismal Wood in the upper reaches of Switzer Creek. Our goal was to explore some old logging roads that were thought to lie between the trail leading uphill from Mountain Boulevard and the relatively new gravel pit behind the Lemon Creek prison.

“It is only five hundred meters between the trail and the pit”, says our F. O., and indeed, so it appears on the aerial photo. Uh-huh! But it’s five hundred meters through an understory of ‘pick-up sticks’—fallen logs and brush piles, which trap my snowshoes and tip me off in unexpected directions, while my friend prances lightly on top of it all.

“Oh, good, here’s the old logging road” (shaped like a trident in the aerial photo). “Let’s follow that!” No brush piles, no logs—should be clear sailing. Ha! The snow is deeper here, with a crust that is just hard enough to let my friend (mostly) dance across the surface, while I break through at every step, post-holing down a foot or more and catching the tip of the snowshoes on the crust as I try to move forward.

Of course, I’m supposed to be throwing sticks for our canine companion and keeping an eye out for interesting natural history as I go…

Pretty soon, we got off the crusty roads and back in the pick-up sticks under the second-growth forest. Eventually, we find a new clearcut, the gravel pit, and what seems to be a small muskeg. Here the crust is firm enough for me to walk on and I can begin to look around. The first thing I notice is that there are no pine trees in this little muskeg, just hemlocks. Very strange—do the seeds not get here, or can they not germinate, for some reason? (But I went back there a few days later, with the F. O. and two four-footed friends, and found cut pines in the slash piles nearby, so our speculation was in vain.)

Then we spot a spider crawling along on the snow and wonder what it might find to eat. We also notice that even the second-growth spruces bear good cone crops this year, but we also find a place where a red squirrel dismantled a hemlock cone, de-winged and ate the seeds. Why bother with a little hemlock cone when there are so many, more calorie-rich, spruce cones available?

So, as usual, we ended up with more questions than answers, which is its own kind of fun. And we had a good workout in that measly five hundred meters. But do I want to go back? Hmph.

(Well, I did, though, but up the gravel pit road on a nice, hard crust, NOT through the Dismal Wood and NOT on the old logging roads. We found porcupine and possible marten tracks, and the path of a deer in a hurry to get across the open ground.)

On another, equally beautiful, day, Parks and Rec (on snowshoes) headed up to a small lake. No one had preceded us since the last big snowfall, so we took turns breaking trail, sinking in to our knees at almost every step. After I had my turn at this, I found that being second or third in line was not a significant improvement, because the folks ahead of me took longer strides on their long legs; I took about five strides to every three of theirs. So it was a serious workout going in; coming back out on our packed trail was a treat!

This little junket also provided some nice conundrums. One was provided by small, slender insects crawling on the snow. Ranging in size from about four to ten millimeters, these stonefly adults had recently emerged from a nearby creek and were on a mating mission. No one really knows why they come out so early in the spring, but stoneflies have so many interesting adaptations that they were a subject for an essay last week.

The best puzzle was found at lakeside, where a tiny rivulet offered about ten feet of open water. A well-worn path led from a nearby burrow in the snow to the open water. There, a narrow opening under the ice gave access to the lake. A dead stickleback lay in the path near the water’s edge. In the other direction from the snow burrow, a less well-used path led to a latrine between some tree roots. OK, so those signs indicate either a mink or an otter.

A few footprints, about two inches wide, showed five rounded toe pads. A footprint of that size belongs either to an extremely large mink or a very small otter. Mink are more likely to be solitary, but small otters are likely to still be in family groups—unless, of course, this individual happened to be dispersing from its natal family or (sadly) the rest of that family had been trapped. We hoped for the best.