Beavers

the many benefits of an underappreciated mammal

beaver-towing-branch-jos
Photo by Jos Bakker

North American beavers were very nearly exterminated from the entire continent by European trappers and settlers. The near-absence of beavers for over 200 years changed the face of the landscape dramatically, not necessarily for the better. As humans took over the landscape and modified it to suit their real or imagined needs, they generally treated the few remaining beavers as intruders into the human domain, to be eliminated one way or another. That attitude still prevails.

To give local examples from my experience: one fellow said he hated beavers because one beaver chewed on a tree in his yard (serious profiling! Not politically correct). And a woman shrieked maledictions upon me, saying that beavers should be killed because they kill trees. DOT worries if pond levels rise along a roadbed or under-road culverts are clogged. Walkers complain if trails are flooded. And so it goes. For some reason, the usual first level of response is KILL them!

But although beavers so often get a bad rap, they are not all bad. In fact, they do some very good work. For instance, in the western Lower Forty-eight states, their dams help reduce erosion, trap sediments, control floods, and raise the water table, resulting in better grazing for ranchers’ herds and better stream quality for fish. Recognizing this, agencies and ranchers have begun to re-introduce beavers in some areas, to the benefit of humans, as well as fish and wildlife.

People often assume that beaver dams block salmon from coming in to spawn, to the detriment of our fish runs. However, adult coho and sockeye can usually jump or slither over most small beaver dams, if there is enough water below the dam to let them gather momentum. Furthermore, the adults are fully capable of waiting for days and days, until rains raise the water levels enough for easy upstream passage. So the common assumption of blockage is often just that—an untested assumption.

Furthermore, scientific research has shown that the ponds formed by beaver dams are superb habitats for juvenile sockeye and coho salmon: they grow bigger and faster there than in other possible sites, so they go to sea in better shape and survive better, and therefore more of them can return as spawners. In fact, in many cases, the size of a run is limited by the amount of suitable rearing habitat for juveniles and juvenile survival. For this reason, fisheries biologists in the Pacific Northwest have reintroduced beavers to some stream drainages, to help restore the waning salmon runs.

Ecologists also observe that beaver ponds are good habitat for nesting ducks, some shorebirds and songbirds, moose, and amphibians. Migrating swans and geese use them regularly. Standing dead trees are used by woodpeckers, chickadees, and certain species of duck. All this research and observation strongly suggest that we humans should take a less simplistic, more multi-factorial approach to beavers and their activities, in fact, an ecosystem-level approach.

Land managers in agencies and private concerns are learning that it is often possible to manage the effects of beaver activity rather than reflexively killing the beavers. There are now beaver-management specialists who offer solutions to many perceived problems—finding ways to keep the benefits of beavers while ameliorating or eliminating the problems. Among the techniques they use are devices known as pond levelers of several designs, diversion dams, exclusion fences of various sorts, baffles to prevent culvert clogging, step pools to facilitate fish passage. Trails can be raised or re-routed. Sometimes all that is needed is making and maintaining notches in dams for water and fish passage while lowering water levels somewhat.

In short, it is often possible to balance the ‘bad’ with the good and find a win-win solution.

 

Early fall in Cowee Meadows

burying beetles, sweetgale ecology, and dragonfly sex

A trip to Cowee Meadows usually provides a curious naturalist with something to contemplate. It’s also a good idea to keep an eye out for large, brown, sometimes temperamental, mammals with claws or hooves.

A stroll out there in mid-August discovered several things of interest.

A desiccated toad carcass lay in the trail, cause of death unknown. The body was attended by two big, orange and black, sexton beetles, maybe just looking for a meaty snack but possibly foraging for a carcass on which to rear a brood of larvae. Sexton beetles are also called burying beetles; they bury the bodies of small mammals and birds (or chunks of dead salmon), denuding them of fur and feathers, which are used to line a chamber housing the carcass. Eggs are laid near the buried carcass and the larvae crawl into the food-filled chamber. Unusual among insects, both parents feed the larvae on liquefied, partially digested meat, as the larvae also feed for themselves on the stored carcass. The number of larvae feeding on a carcass may be regulated by parental infanticide; if there are too many for the available food pile, the parents reportedly reduce the numbers. If for some reason, a female beetle does not have an active partner, she can raise a brood by herself, fertilizing her eggs with stored sperm. In this case, the question in my head was whether or not a desiccated toad would make good larval meals.

The low wetland before the beach berm is thronged with aromatic sweetgale shrubs. They harbor symbiotic bacteria in the root system; the bacteria take atmospheric nitrogen and ‘fix’ it into a form that plants can use. This species usually (but not always) has male and female flowers on different individuals. Male plants have already set their flower buds for next year, while female plants bear cone-like structures with small one-seeds fruits attached to the core. Some small critter had feasted on the seeds of a few plants, leaving the cone-core and fragments in a heap. A fat green caterpillar grazed steadily along the edge of one leaf, not deterred by the reported insect-repellent properties of this species. I was interested to find out that two field guides and two tomes on the flora of Alaska do not instruct a field naturalist how to tell male from female flowers—but the Trees and Shrubs of Alaska by Viereck and Little does!

Out on the beach, it was time for tea and snacks on a favorite log. The tide was low, and far out on a distant rock there was a black lump, which turned out to be an oystercatcher, able to loaf now that the chicks have been raised.

Instead of hobbling over the cobbles around the point, the return trip came back through the grassy/sedgey meadow, where the trails of trampled vegetation left by wandering horses made easy walking in most places. Sparrows popped up out of the tall grass and quickly dove back into the next dense cover. Closer to the river, the vegetation is shorter and marsh felwort flowers began to show up, not only on gravelly soils (as the books say) but also in deep black muck.

The old trail next to the beaver pond has been abandoned, but the water level was very low; there was not even any water in the stream below the dam that makes the pond. That encouraged a little exploration at the edge of the wet meadow along the old trail, which was apparently built (or rebuilt?) without consideration of beaver activity. In recent years, beavers had raised the pond level so the trail was often flooded well over ankle-deep; water was often trapped between the log rails on the trail margins. Rows of young alders have now sprouted up along the edges of that trail, making most of it rather impassible. But the low water level made it quite easy to tromp through the sedges on a parallel route. The newer, improved trail along the hillside would still be the trail of choice most of the time.

Near the beaver pond, dragonflies zipped to and fro, some of them in copula. Male dragons (and damselflies) chase whatever female flies by. If a female is not interested, she may evade the male by running away or hiding; in some species she just plays dead! A successful male grabs a female behind her head with claspers at the end of his abdomen, and they may fly in tandem for a while. The female, if willing, bends her body under his to bring her genitalia (near the end of her abdomen) next to where he has previously stored his sperm in the anterior part of his abdomen, so sperm can be transferred. Copulating dragons make a circle or ‘wheel’ of their bodies. If the female had mated previously, the present male may try to scrape out the sperm of the first male; the ‘opinion’ of the female with respect to this action apparently has not been recorded.

Northern-Bluets-mating-by-bob-armstrong
Photo by Bob Armstrong

Some days later, I watched a pair of bluet damselflies in tandem, perched on a sedge blade in a mid-elevation muskeg pond. The female bent her body up to touch his, in the copulatory position, several times, but they did not form the mating wheel. Three other bluet males patrolled this pond, sometimes zooming in closely on the pair, and even contacting them, as if to try to steal the female away. This is a behavior I’d not seen before. At the edge of the pond lay a dead female, possibly drowned in the act of laying her eggs in underwater vegetation. Some bluets lay eggs in vegetation near or on the surface, but some species of bluet actually submerge the whole body while egg-laying, and upon occasion need to be pulled out by their partner or perhaps by a nearby unmated male.

Wandering

beaver lodges and an outstanding goshawk encounter

Someone once asked me if I go out on hikes and walks looking for something in particular. Many times, I just go wandering with my eyes and ears open, and maybe nothing special is observed, or maybe I get lucky. Sometimes, however, I do have a particular objective, and chance to observe something that is not related to my initial objective at all.

On a recent November stroll near the glacier, I was engaged in a survey of active beaver lodges. Beavers often build caches of branches near their lodges in fall. They pile up branches in a heap that often sticks up above the surface of the water and winter ice. This is the winter food supply; they can just cut off a chunk and carry it to the lodge for lunch. Beavers seldom come out on top of the ice; they are very vulnerable to predators when they cannot dive into deep water. According to the books, adult beavers eat less of the winter cache than young beavers do. The young ones are still growing and need lots of food, but adults can live mostly on body fat that is stored mainly in the tail.

The presence of a cache is a good sign that a beaver family is in residence. However, some lakes with lots of beaver sign don’t have a cache in front of the lodge. I see fresh cuttings and a dam in good repair, but no cache. So the beavers are there, for sure. Then I have to wonder if there’s no cache because there are no young, growing beavers in that lodge; I would love to know!

As I was cruising around, I got a lucky break. As I plodded along, a great flurry of wings beat through the brush. Startled, I spun around, and there was a goshawk in immature, brown and white striped, plumage just rising up into a young cottonwood.

Then I looked at the spot it had come from, and there was the limp body of a young snowshoe hare, still intact. The hawk must have just nabbed it. I quickly went on down the trail, so the hawk could eat in peace. Foot traffic on the trail was scant, so I hoped the predator would remain undisturbed.

About an hour later, I was homeward bound on the same trail, and again the goshawk flushed up into a tree. At the site where I originally saw it, there was only a scattering of fur. The hawk had moved its prey about fifteen feet through the brush. Now all that remained were the guts and hind legs. No doubt the hawk would have eaten more if it hadn’t been disturbed a second time.

I looked around for the hare’s head, and found only the lower jaws, separated and picked clean, and a small assemblage of tiny bone fragments. So I couldn’t add the skull to my collection. But this made me think about the fact that heads provide good nutrition for predators, not only in the musculature but also in the fat around all the nerve cells in the brain and behind the eyes.

Just a couple of minutes later and down the trail a short distance, I saw the hawk flying rapidly off into some spruces. Below its line of flight was a raven in a tree, with a large gobbet of fresh red meat and bone in its bill. The raven had quite a time, organizing its scavenged goodies into a tractable package. Then it, too, flew away.

The deceased hare had acquired part of its winter coat of white fur, so it was a patchwork of brown and white. White fur against a background of dead, brown leaves is very conspicuous, which may have increased the risks for this young hare.

Molting into winter colors in hares (and weasels and ptarmigan) is not keyed to the presence of snow on the ground—although that is when it would be useful as camouflage. The fall molt into winter white is probably triggered by shortening daylength, which does not always accord with the presence of snow. So there are times when hares are just the wrong color for safety.

Outdoor therapy

natural remedies for a downhearted mood

One day recently, I was feeling quite grumpy, disgusted, annoyed, and getting down-hearted, so I decided to cheer myself up by thinking about ‘a few of my favorite things’ that happened in the past couple of weeks.

On Hearthside’s annual author’s cruise, a humpback whale put on a fabulous show. She swam along a shore, pec-slapping vigorously, and then turned around and did the same coming back—sometimes flailing both pectoral fins at once. Then we saw that she had a calf alongside, and the two of them breached repeatedly. They were attended by several sea lions, who jumped and cavorted in and out of the waves created by the breaching. The show had everyone on board in a state of happy fascination.

A trip up Gold Ridge above the tram was a good one, despite the heat that had me just creeping along. The marmots were, sensibly, dozing in their cool burrows (unlike Alice falling down a rabbit hole, I did not fit the burrow entrances—too many cookies, perhaps?). Bumblebees were busy, attending to the tiny blossoms of alpine blueberry growing close to the ground in a tight mat. The alpine zone was a sea of flowers (I counted over twenty kinds, including one that was a complete mystery to me). An American pipit perched on a hot rock, overseeing his nesting territory of alpine tundra and rocky outcrops. Two male rock ptarmigan showed off their brilliant white plumage in soaring flight displays from one rocky tower to another, cackling all the way—still looking for ready females. As the afternoon breezes picked up, ravens began to play in the air currents, sharing air space with hang gliders.

One day I sauntered around some muskegs with a friend, just seeing what we could see (a most enjoyable occupation!). Even though the ponds were mostly dried up, a few held some stubborn water striders, and the mud held evidence of the passage of jays, squirrels, mice, and other small beasts. We noticed a fly bearing an irregular yellow patch on its back, perhaps pollen from a floral visit. It found another fly, which obligingly spread its wings and allowed the first fly—now clearly a male—access to her rear end. They copulated for several minutes; through his beautiful, translucent blue abdomen, we could see his internal organs moving. Together they moved around in the low vegetation; eventually she brushed him off under a twig.

The beavers seem to have returned to Steep Creek, after an absence of several years. We had seen beavers visiting the lower ponds, but this time it looks more serious. The broken dams have been rebuilt and a friend watched a beaver collect a huge mouthful of grass and carry it toward the old lodge. This made me wonder if the grass might be bedding for a young family. There is hope, then, that the beavers may restore the upper dams as well, creating ponds that trap sediment, provide fine rearing habitat for juvenile coho and Dolly Varden, and good foraging habitat for birds. In the past, the sockeye and coho salmon that spawn in this stream proved themselves quite able to surmount the previous dams, and there were good populations of both species in the creek.

The rains came! Not, this time, a source of gloom but of gladness! May was a drought month in Juneau, with very high temperatures on several days. Muskeg ponds dried up, lichens and mosses got crispy, and streams turned into trickles. But the soft rains in early June brought lower temperatures and turned Juneau into its usual lush, verdant self; the creeks flowed again. (And now we are ready for some more sun!)

There, that’s a list of good things observed. Thinking about all that, I found that I was still grumpy, disgusted, and annoyed—oh yes—but it no longer got me down-hearted. Good stuff!—simple things for a simple mind, maybe, but equanimity was restored!

Autumn is here in earnest

the subtle fruits of a somber season

We pass the autumn equinox, and the days get ever shorter. They’ve been getting shorter ever since late June, but now we really begin to feel it. The fall rains are here, and when we look out our windows, we see gray gray gray. It’s seldom as bad as it might look, however, so it pays to get out and about.

In fact, I think that getting outdoors is an important part of living with short days and gray skies. Some folks flee the fall and winter by going south, but I have found several ways to enjoy staying here during those seasons. I try to get outdoors every day, talking a walk on one of our trails; maybe not a long walk, but I’m out in the fresh air, seeing something besides four walls. I sometimes play a game with myself: the challenge is to find at least one thing (preferably three things!) of esthetic or natural-history interest. Sometimes these things are connected: I like to recall the visiting musician who took a walk in the forest and found that the rich variety of green tones in the mosses and ferns reminded him of a piece he had just played; now every time he plays that piece, he’ll see the rainforest. I greatly enjoy the rich cultural life in town, especially the music; the visual and thespian arts are also alive and well, and various lecture series can be both instructive and entertaining. Also, I do best when I have a project or two to work on; it doesn’t much matter if it is writing or building bird houses—a project that engages what’s left of my aging mind.

When I’m out, there are actually several autumn things to look forward to. Great rafts of scoters gather in the coves and channels. It is fun to watch them do what I call ‘chain diving’—a whole line of scoters dives, one after the other, in the same spot; then they all come up, one at a time, a little farther away. I have not yet found anyone who can tell me exactly what they are doing or what food they might be finding or why they do it in that way.

Out on sandy, gravelly bars, there might be small flocks of shorebirds that spend the winter with us. Rock sandpipers and dunlins often hang out together. Adults in breeding plumage of both species have black belly patches, and some show the black blotches as winter goes on, so look closely to distinguish them. These shorebirds breed on the Arctic tundra of western and northern Alaska. Sometimes there are surfbirds on rocky reefs and points; they nest in alpine tundra of Alaska and the Yukon. I occasionally flush a solitary snipe, not only in the marshes and swamps where they might have nested but even along streams in the forest.

I look forward to spotting the first slate-colored juncos that arrive at the bird feeders; they come from the Interior to spend the winter with us. Oregon juncos live here all year but mix with the slatey ones in winter. At present, both kinds of juncos are classified as the same species but different subspecies or races.

Thinking about Oregon juncos reminds me to ask a question: these birds are distinguished from slate-colored juncos in part by a chestnut-brown back. Likewise, our chickadees have chestnut-backs that are lacking in the other North American chickadees. Is there a particular reason why chestnut backs are popular here? Is there something about rain forests that favors that plumage pigmentation?

Of course, the black-billed magpies come to us in the fall too. They temporarily monopolize bird feeders, tease the eagles, and sample leftover salmon carcasses. On a rare sunny day, the iridescence of their black feathers makes them quite spectacular.

Flowering season is over in fall, but you might spot a few late purple asters alongside the trail. Behind the Visitor Center at the glacier, there has been a very late blooming Romanzoffia sitchensis (the common name is Sitka mist-maiden). In the muskegs, look for tiny yellowish cups that might be mistaken for flowers. These are the seed heads of the swamp gentian. Each two-parted cup holds a little cluster of seeds; when a rain drop hits the cup, the seeds get splashed out and so dispersed. This ‘splash-cup’ dispersal is not common, but it is shared by the bird’s nest fungus.

Sept-11-Dan-Moller-11-Gentian-seed-pods-resize
Gentian seed pods

One of my favorite things to do is watch the coho arrive in local creeks. When they do, the bears—which have been waiting for them, ever since the sockeye run ended—get busy again in the streams, and that makes for great bear-watching. I think that many of our local bears really depend on coho to ‘top-up’ their fat deposits in preparation for hibernation. The amount of fat laid down in fall is important in determining how many cubs a female bear can feed while they are in the winter den and it is probably important for winter survival of juvenile, subordinate bears that are not yet expert foragers.

I don’t know all the factors that regulate the size of coho runs, but there is evidence that juvenile rearing habitat is one important factor that helps determine the size of a local coho population. Incoming adult salmon are commonly able to slither over or jump over most beaver dams, so dams seldom limit the spawners. However, juvenile coho rear in pools in streams and in beaver ponds, and research has shown that they grow really well in beaver ponds. Down in the Pacific Northwest, biologists have even re-introduced beavers to certain stream systems, so that their ponds will increase the available rearing habitat for salmon and help restore the diminished populations. Because salmon typically return to their natal stream when it is time to spawn, juvenile rearing success helps determine the size of the spawning run. Thus, when beaver dams are removed from streams where coho spawn (so that their ponds are drained), or when beavers are trapped out of a system and their dams (and ponds) are no longer maintained, and rearing habitat is thus reduced, there is reason to expect that the coho population of that stream will decrease. And that leads to the expectation that the bears living in the area would lay down less fat, possibly survive less well, and produce smaller litters of cubs.

Parental care by males, part 2

these are not deadbeat dads!

This essay will consider male parental care in birds and mammals. Both birds and mammals evolved from reptiles, and some ancient reptiles did have parental care by at least one parent, but modern reptiles have no record of male parental care, so they will be ignored here. As is true for fishes and amphibians, the factors that govern the evolution of patterns of parental care are no doubt several and still subject to debate and future research.

Biparental care is the usual thing among birds: both parents tend the young in over ninety percent of bird species. Females often do the incubating of eggs, but her male may feed her while she does so and the males generally help feed the chicks. This is the case for American dippers, for instance; as one of my field techs said, during our intensive study of this species: there are no dead-beat dads! In fact, we even know of one hard-working dad who raised at least a few of his chicks by himself, after his mate disappeared. The emperor penguin male goes a step further: he incubates a single egg on his webbed feet while his mate goes off to sea and feed; then they both tend the chick.

In some taxonomic groups of birds, including hummingbirds and grouse, females generally do all the work while the males run off to find more females. But even in these groups, there are unusual species in which both parents provide parental care; the willow ptarmigan is a local example.

Still more unusual are avian species in which males both incubate and tend chicks by themselves. Here a few examples. Spotted sandpiper females often lay one clutch of eggs and leave it to the male to do the incubation and guarding while she proceeds to lay another clutch (with the same or a different male) that she incubates and tends; this is a pattern found in several shorebirds.

spotted-sandpiper-nest-Kathy
Spotted sandpiper nest–is this tended by the dad? Photo by Katherine Hocker

In two of the species of kiwi in New Zealand, the Australian emu, and several other species, males incubate and tend the chicks alone. The cassowaries of Australian and New Guinean rainforest also have hard-working males, who incubate the eggs for weeks and then tend the chicks for months. They are fierce defenders of their little families: One day in the Australian rainforest I encountered a cassowary family; we were all looking for fallen fruits. Imagine looking up from the forest floor and seeing a very large bird, almost as tall as you and with claws that could rip you open, glaring at you from just a few short yards away. You can bet I apologized for my presence most abjectly and discretely retreated rather quickly!

What about the mammals? Virtually by definition, females are the ones that feed the infants, and lactation is considered to be the single most expensive thing a female mammal ever does. Dependence of the infants on mother’s milk means that females are always involved in parental care, so uniparental care by males is not an option. Biparental care is not common, but males are reported to be closely involved with parental care in about five percent of all mammal species. The best known cases include carnivores and primates, but regular male care occurs in other groups too. Here are some examples:

Among the carnivores, the males of foxes and wolves regularly bring food to their young. Asian raccoon dog males participate in all forms of parental care except lactation, and also tend the female during the birth process. Male members of packs of African wild dogs bring food to lactating mothers and young pups.

Male baboons and macaques carry babies around, which may help protect the infants from predators or intruding strangers. However, this situation is more complex than that, because the male may obtain direct benefits too: a male with a baby in his arms suffers less aggression from other males and may also gain favor with the infant’s mother. And if there is a fight between males, the infants are in great danger. In some small New World primates called tamarins, including the cotton-top tamarin, males regularly carry and care for babies. Males of the endangered pied tamarin reportedly do most of the parental care except for lactation.

Wild horses and zebras live in groups, often a male’s harem of females plus foals. Males defend their foals and females from predators.

It’s a rare herbivore that helps feed the young ones, but male beaver do: they regularly help build winter caches of branches on which the whole family, but especially the still-growing young ones, feed; they also help maintain dams that make the pools that protect the lodge and facilitate transport of branches. They stay with the rest of the family in the lodge over the winter, interacting and providing body warmth. Among the smaller rodents, males of the California deer mouse reportedly brood the young, keeping them warm until they can regulate their own body temperature. Prairie vole males cache food, brood and groom the babies, and even retrieve them if they wander out of the nest.

Beavers in winter

what’s it like inside a lodge?

On an October exploratory excursion, we encountered a well-built beaver lodge, one we hadn’t known about before. The sides were freshly packed with mud, effectively waterproofing and insulating the lodge for winter. I needed to refresh my failing memory on what it might be like inside a beaver lodge in winter, so back to the literature I went.

Beavers seldom venture into the open air outside the lodge in winter, when ice covers their ponds, so for months a family of beavers breathes ‘indoor’ air, using oxygen and generating carbon dioxide. Beaver lodges have underwater entrances, and mud seals the walls, so air exchange is effected through a ventilation hole in the roof. Apparently this roof vent is sufficient to keep carbon dioxide from building up and allow an influx of oxygen, because when researchers measured the levels of those gases inside an occupied lodge, they stayed nearly constant.

 

Temperatures inside a well-built lodge also do not vary much. For example, when outside temperatures drop to minus twenty degrees centigrade (about minus four degrees Fahrenheit), inside temperatures remain just above freezing. Thick walls obviously conserve more body heat than thin walls, so inside temperature varies more if the walls are thin.

If beavers had to live outdoors in winter, for example at an air temperature of minus twenty degrees centigrade, their metabolic rate would almost double, compared to that at normal lodge temperatures. They might not be able to eat enough to stay alive under those conditions.

Beavers don’t hibernate, so they need a supply of energy throughout the winter months.

Although beavers make a pile of cut branches in front of the lodge as a winter cache of food, the cache does not contain enough food for a whole family of beavers (adults, yearlings, and kits) if they eat as much as they do in summer. Instead of eating lots of cached bark and roots, wintering adults reduce their energy demands by lowering their metabolic rate and body temperature and conserve energy by not moving around very much. The adults put on large amounts of fat in fall, partly in the body cavity and under the skin, but especially in the tail: the amount of fat in the tail in winter can be ten times what it is in summer. This stored fat is used up over the winter, so the adults lose weight.

In contrast, the kits and yearlings maintain their body temperature and metabolic rate, which is higher than that of adults, and they keep on growing. So they eat a lot, and the adults often bring the sticks into the lodge for them to eat.

Just inside the entrance of a lodge is a ledge to which beavers bring sticks from the cache—the winter dining room, so to speak. Here a wet beaver drip-dries as it eats the bark from the branch. A slightly higher ledge is a dry sleeping place where the family spends most of its time in winter. Adults, yearlings, and kits all huddle on the sleeping platform, dozing and occasionally grooming, and sometimes ducking outside to retrieve a cached stick or to defecate and urinate.

lodge-XS-hocker
illustration by Katherine Hocker

If one is very quiet, and the winds aren’t howling nor the rains pounding down, it is sometimes possible to stand next to an occupied lodge and hear the residents chewing on retrieved sticks.

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’!