A minus 4.5-foot tide drew us out to check the intertidal zone. As we strolled across a wide sandy stretch at the water’s edge, we were startled to see a frond of rockweed steadily disappearing into the sediments. A few steps later, another algal frond went quickly down and was gone from our view. Then it happened again. Very mysterious. Some buried critter was pulling in algae, but who could it be? The most likely perpetrators were horse clams, withdrawing their siphons as our steps shook the sands and thus pulling down algae that were attached to the siphons.
We found several Aristotle’s lanterns, the grazing apparatus of sea urchins, left behind by birds that had cleaned out the urchins’ soft innards. I was interested to see that every lantern had a ribbon worm wedged into the intricate structure.
The big whorl of Neptunea whelk egg cases that we found in May was still there, with the presumed parent still nearby. But now the egg cases were open. We had thought, in May, that the whelk was just-then laying the eggs, but a month is too short a time for them to have hatched, so some predator may have got them.
We often find sea stars that are missing one or two arms, and sometimes they are in the process of regenerating them. But on this day, we found a sea star that had lost four of its five arms, and the regenerating arms were still very small. With only one functional arm, this star would find it hard to pry open clams or mussels or pull big snails off the rocks. I’m guessing that it would have to rely on small prey that requires less manipulation, but regenerating four full arms would take a lot of energy. I wonder if any researcher has ever studied the energetics of regenerating missing arms or the possible changes of diet for sea stars with many missing arms.
I noticed two black oystercatchers, unusually quiet. Then I saw that those two were accompanied by another one—it was back-lit, so colors were not clear, but it was slightly smaller and had a shorter bill. Aha! Parents with a big chick. They moved off without fuss to another rocky point.
And now a bear story: Sometime in May, I came home and looked out my front window. There was something large and black in the spruce tree across the pond—right where the pulley line for the seed feeders is attached. The feeders hang over the pond, where the spill is relished by a bunch of mallards. The large black creature tugged repeatedly on the pulley line with her claws and then with her teeth, but to no avail. She gave up, came down the tree, and came around the pond into the yard to eat horsetails, then ambled all around the house, sniffed some primroses, and went back to the other side of the pond. There she climbed a small pond-side alder that bent low under her weight, so she was then balancing—and wobbling—over the water on a trunk that was much too narrow for her bulk. Soon she was upside-down under the alder, like a sloth. She let go with her hind feet, so then her butt was in the water, and used her front feet to inch her way sideways along the trunk to shore. She stood quietly on the bank.
Now the pair of mallards that had been watching her shenanigans from the safety of the middle of the pond began to take closer notice. Mr Mallard suddenly and loudly lunged at the peaceable bear on the bank—and she scampered quickly up a tree! After she came down, he did it again—and she scooted up another tree! And then she ambled off into the woods. A friend noted, later, that I have ‘watch ducks’.
The day dawned gray and cool, with a sharp breeze coming down from the north and big swells rolling in from the south. The combination of swells with the chop from the opposite directions would make for interesting paddling.
On the previous day, we’d notice clouds of white birds over on the Berners River, so we knew that the eulachon must be headed upstream. The herring shoal that entertained us last night had moved on, and we intended to check out the action at the eulachon run. The plan was to paddle across to the west side of the bay and hike up along the Berners River.
The tide was starting to go out, which meant that finding a good place to park our kayaks near the mouth of the Berners River would be difficult. Vast amounts of silt come down the rivers into the bay, creating a broad apron of shallows all across the north end of the bay. If we left our boats anywhere along the shore at low tide, they could be stranded far from water deep enough to float even a kayak (unless we waited for hours, until the tide rose again). Parking on the inviting sandy beach would mean that we’d have to carry our boats hundreds of yards over the tideflats to reach navigable water. So we hauled them up on some miserable, slippery, slimy rocks on a steeper shore, where the distance to water would be less.
Snowbanks still lined the fringe of trees above the high tide line, but spring was indicated by a few nearby wildflowers in bud and bloom. The cold north wind spattered our glasses and binoculars with rain as we trudged up the edge of the tideflats, but the white clouds of gulls drew us on, up the river.
The sandy flats, exposed by the outgoing tide, held a record of other recent visitors. A pair of moose had just passed by, leaving one set of very large footprints and another set of somewhat smaller ones (?perhaps from last year’s calf?). In the fringing willows we also noted many broken branches where wintering moose had pulled down twigs to eat. A beautiful trail of an otter was so clearly defined that we knew this animal had been there that morning. There were slightly fuzzier prints of mink and a possible wolf, from an earlier time.
Most interesting, maybe, were the large prints (about seven inches wide) of Brother Bruin, ambling up and down the gravelly shore. The shape of the foot pads suggested ‘brown bear’. A large and very fresh pile of fist-sized droppings hinted at the possibility that we might be under observation ourselves.
With all the interesting things along the way, our progress was slow. Eventually, however, we got far enough upstream to watch the gulls snatching fish and trying to steal fish from each other. Dozens of eagles stood around on the sand bars or perched in the trees, just watching; since ‘taking turns’ is not likely to be part of eagle etiquette, perhaps they were sated. In some of the slightly deeper channels, we could make out long columns of dark forms slowly swimming upstream, running the gauntlet of predators.
On the way back to our boats, we noticed wads of what looked like tiny eggs, washed up on the sands. Our best guess was that these were eulachon eggs that had stuck to each other rather than to sand grains. Eulachon eggs have a double membrane around them. The outer one breaks open and folds back to make a little pedestal that normally attaches to a grain of sand. The egg then incubates in cold, fresh water until it hatches and the tiny larva washes out to sea. But these clumps of eggs (if that’s what they were) were doomed, all stuck together and getting washed into salt water way too soon.
After lugging our boats about a hundred yards back to floatable water, we headed back to the cabin. The water was smoother now, and the going was easy. A squadron of about forty sea lions reared up, giving us the eye and a continuous roar as we went by—a trifle unsettling, even when you know it’s all talk.
So the weekend was a huge success. We’d won the lottery and got to the bay when things were happening, with a bonus of many other attractions, including good company. Our cups were running over, leaving lots of good memories.
little snow stories, a fungophile squirrel, and long-leg aggregations
Wonderful snow! Brightening our short December days; under that full moon, it was spectular.
All that glorious snow drew me out, day after day, looking for little stories writ there. There were all the usual perpetrators: deep, winding furrows made by wide-bodied, peripatetic porcupines, lots of snowshoe hares (especially near the visitor center), a mink bounding over a frozen rivulet, red squirrels tramping back and forth between trees, a deer or two—or lots in some places, an ermine, some good otter slides, a few voles and shrews (and a couple of mysteries that I shall gloss over).
There were also a few real highlights. Out near Peterson Creek, after watching a hungry dipper searching for some open water, my friend glanced up and spotted something odd-looking about ten feet up a spruce, right next to the trunk. This looked like a mushroom, stuck in a tuft of twigs. Really? So my friend climbed up, to look more closely. Indeed, not just one but five or six mushrooms were wedged in a tight stack, in among the twigs. Ha!—a squirrel cache. Red squirrels are known to store mushrooms in dry places, such as the tops of well-drained stumps or logs (but cones are usually stored in damp places, so they don’t open and drop the seeds). This squirrel clearly thought that the twiggy tuft was good enough to warrant stashing several valuable food items there.
The sloping base of a huge spruce in Amalga Meadows had been an active site. Small prints of a critter that could bound six or eight inches decorated the trunk up about three feet, as well as all the surrounding snowy ground. Hmm, not a vole, which usually scuttles along, nor a jumping mouse, which hibernates, but probably a deer mouse.
We looked out over the wind-swept open area of the meadow, where the snow had been draped over tussocks and small conifers. We saw immediately that these looked like sea lions lunging up from the water. There was a big, thick-necked bull, and a whole squadron of juveniles, not far behind. No great imagination needed to provide some sound effects as well!
Some friends like to explore old mines in the Juneau area and recently explored one near the base of Thunder Mountain. The adit was barricaded by stout icicles, but a few were persuaded to break, allowing human entrance. Not too far back in the tunnel, observers spotted a number of harvestmen (a.k.a. daddy longlegs) on the wall. Near the end of the eighty-foot adit, many of these were clustered into a close group, with their long legs sticking out in all directions.
Harvestmen are related to spiders, but not very closely. In contrast to spiders, they are not predatory; they feed chiefly on bits of plant and animal debris. They are also not venomous and cannot bite you with their weak jaws. They are often gregarious, gathering in bunches, but why? One suggestion is that they are behaving like what is known as a ‘selfish herd’. Each animal tries to put as many others as possible between itself and the edge of the group, where the risk of predation is highest. For these harvestmen, the most likely predators are spiders, or possibly mice.
In June, we witnessed an explosion of tiny flies that swarmed in dense clouds. These mating swarms of March flies were so common that the Empire carried a story about them (22 June, 2012). The flies are short-lived, and their bodies accumulated on the surface of muskeg ponds and along the shores of Mendenhall Lake, where birds gobbled them up. Some of the March flies arrived, by choice or by wind, on the slowly dwindling snowbanks on Gold Ridge, above the tram. The surface of the snow was dotted with their tiny bodies and even with a few still living. Some were lively enough, however, to make their way to early flowers blooming in the snow-free areas.
Many of the remaining snowbanks had reddish streaks and patches. Going by the informal name of watermelon snow, both for the color and a faint aroma, it is actually an alga that lives on snow. It is common worldwide in alpine areas and polar regions.
Technically, the snow alga is a single-celled green alga, with chlorophyll that captures sunlight to fuel the process of photosynthesis, by which green plants build carbohydrates, releasing water and oxygen. However green it may be underneath, it ultimately turns red, from molecules that protect the green, photosynthetic pigment from intense UV radiation. In winter, the alga is dormant in the soil and contains antifreeze to protect it from freezing, but come spring, the dormant cells release several smaller, green cells that have two whip-like hairs called flagella. Using the flagella, the little green cells recolonize the spring snow by swimming upward through the snow to the surface layers. At some point, they acquire the red color. At the surface, they may form thick-walled resting cells capable of enduring desiccation and summer temperatures and waiting for the next snow season. Or they may fuse in pairs to form zygotes–the product of sexual union, and then become dormant, later dividing into the swimming cells to recolonize a new layer of snow.
Snow algae build their carbohydrates for energy, but needed minerals are derived from wind-blown dust and bits of organic debris; they get needed water from slight melting of the snow. They are eaten by a variety of micro-herbivores, including protozoans, rotifers, nematode worms, ice worms, and springtails. These grazers are, in turn, eaten by mites, spiders, and insects, which often end up in the stomachs of alpine songbirds. The pipits, rosy finches, and occasional robins and sparrows also gorge on insects that are blown up the sides of mountains, eventually becoming immobilized by the cool temperatures at higher elevation. A condign fate for all those March flies too!
Gold Ridge had other things to offer that day too. There were long-abandoned ptarmigan beds, where the birds had spent the night in a snow-burrow that was now exposed by snow-melt. We found a strange pellet about two inches long, just lying on the snow. Close inspection revealed lots of little pebbles stuck together and—aha!—pieces of shell, including a recognizable fragment of barnacle shell. So the perpetrator was probably a raven that had been foraging along the shoreline and had unloaded this clump of indigestible bits.
A few flowers were blooming, such as the tiny primrose called pixie eyes, a mat-forming plant known as alpine azalea, some adventurous lupines and valerian, Cooley’s buttercup, hairy cinquefoil, and caltha-leaved avens.
Our peaceful sojourn in the alpine was terminated by the temptations of dinner-time and rising winds that presaged a change from our brief spell of post-solstice sunshine.
shoreline bird sightings, frost sculptures, and a startled grouse
One day after a nice little snowfall, I ambled out to Point Louisa in Auke Bay. The usual squads of harlequin ducks sallied out from the rocks or poked along the boulders. A few common and Barrow’s goldeneyes sailed by, some of the males half-heartedly beginning a courtship routine. A stray sea lion and a harbor porpoise swam by, looking for something tasty.
The best of the avian sightings was a little flock of black turnstones, calling as they flitted from one patch of rockweed to another. They only come to us in winter; they nest in western Alaska and winter all along the Pacific coast. These were not flipping little rocks—the behavior that gives them their name—but rather were merely pecking and poking for small invertebrates among the fronds of the rockweed. All of them were in winter plumage. But, unlike the photograph, most of them showed snazzy black crescents along the flank below the wing. These are created by small feathers that cover the bases of the inner flight feathers, and sometimes they hang down over the flanks. I have not been able to find out if the crescents show only in certain circumstances, and they are only illustrated in a few bird guides.
The snow on the upper beach told stories. Shrews had made their narrow grooves as they ‘swam’ over the snow. A vole, heavier than a shrew, had waded through the snow from log to log, leaving a wider groove and a few footprints. An older set of tracks showed that a weasel had snooped into grassy tussocks and under logs, covering a good bit of ground in its search for dinner; it had missed both this shrew and the vole.
Up in the forest edge, a varied thrush prospected for anything edible and small, junco-size tracks hopped around under the brush.
A few days later, we entered a prolonged deep freeze. Everywhere I went, hoar frost decorated all the weeds and branches that were not under the forest canopy and spangled the ice wherever the snow had blown off. I strolled with friends around the rainforest loop near Eagle Beach State Park and ambled around in the Dredge Lakes area. The best bird we saw in the Dredge area was a rusty blackbird at the edge of the ice that fringed some open water; it was hunting for bugs in the water and found some. That’s exactly what dippers do in winter, and this bird fooled me for a minute.
I found it fascinating to observe the tremendous variety of forms the frost could take. I don’t know exactly what determines each variant and I probably don’t really want to know—much too complicated for me! But I can appreciate the wonderful forms anyhow. On a metal bridge we found flat, visually simple blades of frost, very different from the visually complex blades on many twigs. The more complex ones were as individually distinct as snowflakes are, and were composed of crystals oriented in many different ways. Some were flat and blade-like, but in some cases, the crystals took the form of tiny trees, with branches in all directions. Down on the bare ice, the spangles took the forms of flowers, or birds, or butterflies, each one originating from some little irregularity in the ice. A few days later, a light snowfall piled up on the ice-spangles, creating lumpy little muffins.
In the middle of December, after high winds had snapped off three snow-laden trees near my house and most of the wreckage had been cleared away, I plodded my way in to Tolch Rock and made the loop around by the gravel pit to the road. The trail was not obvious all along this route, but some long-legged, large-footed chap had plowed through the overhanging brush before the last snow fell, making it easy to find the trail once it was ‘misplaced.’ The only exciting thing was flushing a grouse, who took off with thunderous wings, and gave me a good jolt (question:.why don’t grouse turn white in winter, as ptarmigan do?) The snow was perfect for tracking critters, but very few small ones had been out. In contrast, the snowshoe hares had had a party! A mink had visited a tiny trickle that feeds into the smelly ditch near the entrance to the campground, and a mallard drake cruised by in that fetid ditch. Sometimes I even see dippers foraging in that sorry stream.
When I got up that morning and looked out the window, rain was cascading down. This is spring, so I really didn’t want fall weather. But I glumly packed up my gear, somewhat grumpily donned my rain pants, made sure my rain jacket was in the car, and went to pick up some Parks and Rec hiking friends. By the time we reached the Perseverance trailhead, the sky was blue, the sun had climbed over the ridges, and with smiling faces we headed up the trail (after greeting the large, furry, white dog that lives in the Gold Museum and likes to check out folks at the trailhead).
Spring is always quite exciting, because there will be something new to see or hear or smell almost every day. In the past two or three days, leaves had fairly leaped out of their buds, and cottonwood leaves glittered in their new-green hues. Salmonberry canes sported their first pink flowers, and clumps of shooting stars decorated the trailsides. My favorite yellow violet was in good flower, along with the small-flowered lavender one. The air was fresh with the delicate fragrance of cottonwood resin (on the bud covers) and the sweet perfume of skunk cabbage (nothing the least skunky about it!).
Robins carried food to their chicks, and parental varied thrushes clucked warnings to their newly fledged youngsters. Wilson’s warblers chattered on all sides and a few yellow warblers announced their recent arrival. Fox sparrows held shouting matches (in song) in the thickets. Ruby-crowned kinglets gave many variations of their rich, musical song. A few hermit thrushes fussed in the underbrush but did not sing. A pair of harlequin ducks loafed on a midstream rock, presumably with thoughts of eggs to be laid in a nest not far away.
Where Lurvey Creek joins Gold Creek, I gazed upstream for half an hour and was finally rewarded by a small gray bird that darted out of a crevice in the cliff and perched on the deep snowbank that lined one side of the creek. Dippers often nest here, except in years when snows still cover the entire creek. A snow-bridge below the dipper’s nest site collapsed bit by bit and sent snow-bergs downstream, as we enjoyed a leisurely lunch with homemade cookies.
If we had been there two days later, things would have been really exciting. Big slabs on the flank of the ridge loosed their moorings and slithered down into Gold Creek, just above the junction with Lurvey Creek. A deep mound of dirt and boulders now squats over the creek, which has carved its way through the debris. Gold Creek was turbid for several days, and this is likely to continue for a while, given the size of the dirt pile. The heavy sediment load is probably bad news for the dippers trying to nest downstream, because the water is too opaque for them to find their food.
A warm day or two later, I was on the West Glacier trail, finding the first baneberry flowers, lots of buttercups, more violets, and batteries of white butterflies looking for mates and visiting the violet flowers. On damp, rocky sites we found clumps of a flowering plant that was new to me until very recently. It goes by the utterly silly common name of Sitka mistmaiden (more formally known as Romanzoffia sitchensis), and it looks enough like a saxifrage (which it is not) to fool a botanist. This trip had the ultimate goal of checking for a dipper nest at a stream that plunges off Mt McGinnis into Mendenhall Lake. And indeed, the birds were there, although this year the nest was in a new site across the creek. I think that dippers started nesting by this stream as soon as the glacier left the site open.
The next Parks and Rec excursion was a stroll out to Blue Mussel cabin on the shore of Berners Bay. Overcast skies kept the temperatures relatively cool, and mist lay low over Lynn Canal. We gobbled up a homemade rhubarb dessert (yes, mom, even before ‘cleaning our plates’), as small squads of sea lions foraged enthusiastically and a humpback whale made unexpectedly tight turns in pursuit of the same small fishes.
Although our spring arrived late this year, the meadows were awash in pink-flowered shooting stars. Bright yellow buttercups dotted the fields of pink, yellow marsh marigolds adorned the wet ditches, and the yellow display of skunk cabbages attracted the usual crowds of small, brown, pollinating beetles. Lupine was just beginning to bloom, but these early blooms had already been visited by bumblebees, turning the upper petals from white to magenta.
I heard a snipe performing its great aerial display, but I think I was the only hiker who noticed this. Savannah sparrows sang and flitted low in the herbage, and I heard a distant burbling song of a Lincoln’s sparrow (but I had to think hard for a bit before I could pull that one out of my so-called memory!). And I have not mentioned the mosquitoes…
On the walk between the beach berm and the Blue Mussel cabin, we encountered several signs that the trail is also used by bears. There was a strange, barren patch of forest, in which there was no ground cover and all the smaller trees were quite dead. It looked as if a ground fire had passed through, but there were no signs of charring, leaving the cause an open question.
Considerable work has greatly improved the formerly squishy trail between the Cowee Meadow cabin and the beach berm, where sweetgale was just leafing out. However, parts of the trail through the meadows were ankle-deep in water, nicely contained between the logs that mark the trail edges. A few more loads of gravel between the logs in these sections would surely be appreciated!
feeding a diverse group of animals… including humans
Walking along the East Glacier trail one day, I noticed a scattering of gray lichen scraps on the snow next to a small tree trunk whose lichens were the source of the scraps. Some small creature had ripped off much of the lichen, leaving the bits on the snow. A narrow groove led away from the lichens to a small burrow that led down under the snow blanket. That made me think a shrew had been rooting around in the folds of the lichen for insects or spiders, but it was also possible that a small vole had been selectively feeding on the lichen itself.
A few days later, on the Spaulding Meadow trail, I was following some deer tracks, to see where they were going, when my more observant companion called my attention to where the tracks had come from.
There, not far from the trail, there was a noticeable browse line in the arboreal lichens (witches’ hair or Alectoria) hanging from the tree branches, and underneath there was a multitude of deer tracks. All the Alectoria lichens below a certain height, within reach of a foraging deer, were missing from that patch, although they could be found not far away where the deer had not walked.
These observations made me think about lichens as a food source for animals, and I have a very helpful local lichenologist to thank for some great references (as well as instruction on lichen identification). Some lichens are not very tasty, some are actually very poisonous, many have defensive chemicals to deter consumers, and yet a great many critters eat them, often quite selectively.
Somewhere in the world, lichens are eaten by certain snails and slugs, as well as certain kinds of mites and moth larvae; some of these consumers actually specialize on particular kinds of lichen. Although lichen-eating invertebrates have not been well studied in Alaska, we do have a local snail or slug that grazes on the outer layers of leafy lichens. (Recall that a lichen is a composite of a fungus and an alga or bacterium—and some lichens have all three components). Occasionally, if you look closely at the leafy lichens, you might see tiny white trails on the greenish or brownish lichen surface. These meandering trails reveal the white fungal layer below the outer layer, showing where a snail or slug has scraped off the nutritious outer layer that includes the algae or bacteria that also make food for the lichen.
We know a bit more about vertebrates that probably or actually do eat lichens in Alaska.
Caribou are surely the most well-known consumers of lichen all across the North. They use their hooves to dig craters in the snow so they can reach terrestrial lichens, particularly the shrubby, branching ones such as Cladina (reindeer lichens), Cetraria (Iceland lichens), and Stereocaulon (foam lichens), or leafy ones such as Peltigera (pelt lichens). Where there are trees and arboreal lichens, Alectoria (mentioned above) and Bryoria (horsehair lichens) are favorites. Caribou eat lichens all year long, but especially in fall and winter; in spring and summer they consume more willows and herbaceous plants. Apparently, their digestive enzymes change with the seasons, becoming better able to deal with lichens in winter. But lichens are mostly carbohydrate, with low values of protein, so caribou have to find some other source of protein or a means of coping with low levels of nitrogen.
Some reports indicate that each caribou has to consume ten or twelve pounds of lichen per day, so a whole herd can make big inroads into lichen populations. Intensive caribou grazing can wipe out whole communities of such lichens, leaving only the low-growing or crust-like ones, and it can take decades for the lichen community to be restored. The most famous example concerns the introductions of reindeer (Eurasian caribou) to St Paul Island in the early 1900s. From just a few animals, the population grew by leaps and bounds, and they ate up virtually all the edible lichens, so their population crashed dramatically. They truly ate themselves out of house and home.
In Southeast, Sitka black-tailed deer eat arboreal lichens, as we observed, and so do moose. When mountain goats descend from the peaks into the forest in the winter, they eat arboreal and leafy lichens; in the alpine zone in summer, they may eat branching, terrestrial lichens.
There are several species of red-backed voles in western North America and two of them are known to eat both arboreal lichens and branching, terrestrial ones; I found no reports specifically for the species that occurs in Southeast, but it is likely that this species does also. Flying squirrels are important consumers of arboreal lichens (as well as using them to build nests).
All these lichen-eating animals are important parts of the ecosystems of Southeast, so it is useful it is useful to consider a few of the ecological interactions that ramify from this lichen base. Some lichens accumulate certain organic pollutants, which are then passed on up the food chain to caribou and deer, and thence to predators such as wolves and humans, where the pollutants become concentrated. Industrial pollution and extensive logging can devastate lichen communities, drastically decreasing the food supply for all of the many consumers. Loss of this important food supply has repercussions in many directions: for example, flying squirrels and voles also eat truffles and disperse the spores when they defecate; truffles are mycorrhizal, making nutrient exchanges with the roots of many trees and supporting healthy tree growth. Caribou, moose, and deer help support predator populations (predators that also prey on other species such as hares and salmon); the browsing of these herbivores can alter plant communities and affect the reproduction of shrubs such as willows and blueberries, which in turn affects bumblebees (that feed on willow and blueberry flowers and go on to pollinate many other kinds of flowers) and birds and bears (that eat blueberries and disperse the seeds).
Humans, too, have made extensive use of lichens as food. Indigenous people of the North ate partially digested lichen from caribou stomachs; this material was mixed with fish eggs to make what was considered to be a delicacy (presumably an acquired taste?). In some parts of the world, lichens have been fed to domestic animals, including pigs, dogs, sheep, and cattle, and humans themselves have used lichens as flavoring, thickener for soups, and emergency food.
Historically, the biblical manna from heaven, which is said to have sustained the migrating Hebrews in the desert, could have been one of the so-called vagrant lichens, which grow loosely on the ground and can be blown hither and yon by a wind. Many things have been called ‘manna’, including plant resins, honeydew from scale insects and aphids, and certain mushrooms, but vagrant lichens seem especially plausible as the biblical manna, because they would take up water (and expand) after a rain or morning dew, and they can accumulate in some density after a wind (and dew, rain, and wind are all mentioned in one biblical account or another, in association with the appearance of manna). Lichen-manna is quite edible (to humans, camels, and sheep in the Old World, as well as pronghorns in the Idaho high desert) and can be made into bread, but some reports say that it should be eaten in small quantities.
Although lichens seldom claim much of our attention, it should be clear from these considerations that they should not be neglected!
the interesting life of a perhaps-underappreciated fish
There are many species of sculpins in Alaska, mostly living in intertidal zones. One of the species a shore-bound person is most likely to see is the staghorn sculpin, so-called for the little ‘horns’ or spines on the rear edge of the preoperculum (a bone that helps cover the gills). Staghorns can be as long as 46cm and many live for several years. They are common in estuaries, but venture into fresh water as juveniles. As they grow older, they may move into deeper marine waters, down to about 50m, but many spend their lives in estuaries.
They don’t have any scales on their bodies, like some other sculpins, but which is unusual among fishes. They have very large pectoral fins that can be fanned out to the side. These are used for locomotion (forward or back), gliding down to deeper waters, or propping themselves up on a rock while they wait to spot a tasty prey item.
I got interested in staghorn sculpins after observing American Dippers capture them. Dippers often eat small fish, up to four or five inches in length. That’s a lot of fish for a bird that only weighs a couple of ounces. So dippers generally pound a captured sculpin on a handy rock, sometimes thrashing it as long as ten minutes. This subdues the squirming fish, makes the fins relax, and eventually may break the fish’s body into pieces, which are then consumed. A small sculpin, however, may be swallowed whole, headfirst, after being subdued. In winter, dippers often forage in estuaries, so sculpins are captured rather regularly.
These sculpins mature at age one year, and keep on growing. A large female can lay up to 11,000 eggs; some sculpin eggs are poisonous, but I have not been able to confirm that for staghorns. As in most (but not all) sculpins, in this species eggs are fertilized externally, as males and females just extrude their gametes into the water, during the winter months. The eggs are laid on rocks, where males tend them for about two weeks, depending on water temperatures. The larvae eat plankton and are found chiefly above the bottom. They turn into juveniles when they reach about 20mm in length and into adults at about 120mm in length. Juveniles and adults live on the bottom, where they eat amphipods, shrimps and crab, and worms; large juveniles and adults eat fish and large crabs.
One of their more interesting ways to feed themselves is by nipping off the siphons of clams. Reportedly, if a staghorn chances to bite the siphon of a butter clam that carries PSP, it may avoid them thereafter; although it will continue to eat siphons of clams that do not carry PSP. So PSP may help protect the clams from sculpins! If staghorns are prevented from chomping on the siphons of littleneck clams, these clams can then grow at twice the rate of clams with nibbled siphons. So there is a big cost to getting chomped by sculpins, and protection would be valuable.
Staghorn sculpin are eaten by many different marine mammals and birds, including large fishes (other sculpins among them), ducks, loons, herons, cormorants, pigeon guillemots, river otters, and sea lions. They are so vulnerable to predation that they have several means of trying to protect themselves. They may try to avoid being captured by partially burying themselves in bottom sediments. This doesn’t always work. And they erect those spines, with the sharp ends pointing up, if somebody threatens or grabs them. But some predators know how to avoid the spines. In addition, staghorns are cryptically colored in blotchy browns and grays, which makes them relatively inconspicuous. I would like to know if staghorn sculpin can change color, as some other species of sculpin do.
Researchers at UAS have studied cryptic coloration in another species of sculpin, the coastrange sculpin. This is a freshwater species that is also cryptically colored. Coastrange sculpins can change their colors to match the bottom of the stream, becoming darker or lighter, depending on the background. Some color changes take weeks, because new pigment cells in the skin have to be created or destroyed. But these sculpins can also change color quickly, in just a few minutes, by expanding or contracting the pigment cells. Some individuals are able to make greater changes than others. For example, small sculpins tend to be able to make greater color changes than larger ones.
The value of color shifts became apparent in simple experiments showing that light-colored sculpins on a dark background and dark sculpins on a light background were more often attacked by predators than sculpins that closely matched their background. Thus, the ability to change color is clearly adaptive. Interestingly, fish from a turbid stream with little overhanging vegetation exhibited more variation in color change than fish from a clear stream with lots of nearby vegetation. The researchers suggested that there would be a lower risk of predation in the turbid, unvegetated stream, because the sculpins would be less visible and there would be fewer predators. As a result, the ability to make rapid color changes when a sculpin changed its position and therefore its background, was less important there. Therefore individuals of differing ability to color-change could remain in the population. Where the risk of predation was thought to be greater, the researchers suggested that all individuals would gain protection by the ability to change color rapidly whenever they moved around, so there was less variation among individuals—the individuals that couldn’t change rapidly got eaten. Natural selection at work.
This work was done largely in Glacier Bay, which has been gradually deglaciated in the past two hundred years or so, and streams near the mouth of the bay are older than those near the still-receding glaciers. As a result, streams near the glaciers are turbid and surrounding areas have little vegetation, while streams near the mouth of the bay are clear and well vegetated. As the streams age, the risk of predation and the color of the stream bottom change, so the ability of sculpins to change color probably has helped them to colonize streams in the bay.
Wolves have been persecuted by humans almost everywhere, to the point that they are extinct over much of their former geographic range. Although they have been reintroduced to a few areas, they are still subject to human trapping and shooting (both legal and illegal) in most parts of their present range and humans are the single most important factor determining wolf numbers in most areas.
Even in the absence of human interference (or at least where the human impact is light), adult wolf densities vary enormously. Some of the variation is geographic, depending on prey type and availability. Some of the variation is temporal, again depending partly on prey availability, but also on other factors, such as disease, which can reduce wolf numbers markedly. (At least one disease apparently originated with domestic dogs, and others are carried by dogs, so even this factor is partially related to a human impact.)
Most wolf researchers agree that, in general, wolf densities are correlated with the food supply. A summary of 31 intensive studies showed a significant linear correlation between average wolf numbers and average biomass of ungulates in an area (i.e., numbers and sizes of moose, deer, caribou, etc.), accounting for 64% of the variation in wolf density (Fuller et al. 2003). Many individual studies arrived at the same conclusion.
In any single year, however, a close relationship between wolf density and ungulate prey biomass may not be found, in part because of time lags between changes in prey biomass and the wolf population response. Furthermore, estimating prey availability as simple biomass of ungulates can only be a rough indication of food availability, because various other factors affect the vulnerability of ungulates to wolf predation and need to be considered; e.g., distribution (deer density can be lower near the centers of wolf pack territories, where hunting pressure is higher), season (snow depth in winter reduces ungulate mobility), and prey health (ungulates are subject to some debilitating diseases). In addition, the availability of alternate prey such as beavers and hares would affect the closeness of the relationship.
In addition, human impacts on both wolves and ungulate prey affect the relationship between wolf numbers and their food supply, producing variation around the linear correlation: Where wolf numbers have been markedly reduced by humans, or where wolves have only recently been protected, the ratio of wolf numbers to prey tends to be low; that is the wolf population is below the limit set by its prey base. When wolf numbers are low relative to the food supply, reproductive rates and success can be high. Litter size tends to be larger and pup survival is better when food is plentiful. Therefore, a depleted wolf population can restore its former numbers in just a few years, and a newly established or protected wolf population can soon reach the limit of its food supply. Immigration from neighboring regions can add to the rapid recovery.
Because of the ability of depleted wolf populations to recover rapidly when food is abundant, programs of wolf control have to kill many wolves in order to reduce the population size. For example, in the Tanana Flats, AK, a seven-year control program reduced a population of 239 wolves to about 143 individuals, a reduction of 96 wolves. To do so, program killed 337 wolves. That amounts to roughly 3.5 wolves killed for every single wolf reduced from the population.
On the other hand, where wolves are not exploited by humans, or where ungulate prey is heavily harvested by humans, the ratio of wolf numbers to prey tends to be high; that is, the wolf population is near the limit set by the prey base. If the ungulate population is severely depleted by humans, the total number of wolves it can support must be small.
Particularly when wolf density is high relative to the food supply, the relationship between wolf density and food supply is mediated, in part, by social factors. Then reproduction may be inhibited, more individuals may disperse from their home packs, and lethal strife among wolves may increase.
Obtaining good data on wolf populations requires intensive field work. All studies of wolf population regulation depend on accurate census data from field surveys in the area of concern. Because wolf population sizes vary geographically and temporally, it is not sufficient just to assume that information from one time or place can be applied to another. Reliance of the reports of trappers and shooters for estimates of wolf population size is totally inadequate.
Fuller, T. K., L. D. Mech, and J. F. Cochrane. 2003. Wolf population dynamics. Pp. 161-191 in Wolves (eds. L. D. Mech and L. Boitani). University of Chicago Press, Chicago.
Hayes, R. D. and A. S. Harestad. 2000. Demography of a recovering wolf population in the Yukon. Can. J. Zool. 78: 36-48.
Van Ballenberghe, V., A. W. Erickson, and D. Byman. 1975. Ecology of the timber wolf in northeastern Minnesota. Wildlife Monographs 43: 1-44.
Van Ballenberghe, V. and L. D. Mech. 1975. Weights, growth, and survival of timber wolf pups in Minnesota. J. Mammal. 56: 44-63.
Vucetich, J. A. and R. O Peterson. 2004. The influence of prey consumption and demographic stochasticity on population growth rate of Isle Royale wolves Canis lupus. Oikos 107: 309-320.
Wydeven, A. P., T. R. Van Deelen, and E. J. Heske (eds). 2009. Recovery of gray wolves in the Great Lakes region of the United States. Springer, NY.
leaf-rolling larvae, dancing butterflies, and scuttling shrews
Little rains had persisted for days and days, with no end in sight. Nevertheless, a friend and I took off up the trail and, much to our surprise, the sun peeked out and no rain fell until we were home again!
On the way up Perseverance Trail, we noticed a number of rolled-up cottonwood leaves lying on the ground. When unrolled, each leaf revealed a network of silken webbing and a collection of small black pellets, indicating the former presence of a moth larva. The larva had eaten a third to a half of the leaf, digested the tissue and excreted the pellets, and rolled the remainder of the leaf as a protective shell around it while it grew. The trees dropped the damaged leaves, and the larvae crawled into the soil to pupate while then transforming into adult moths that will fly later in the summer.
Margined white butterflies fluttered over violets and buttercups, the white males outnumbering the more dusky females. Although it was now July, songbirds still sang, presumably in the interest of starting second broods of chicks. Fox sparrows were heard most commonly, but there were also a few Wilson’s warblers, yellow warblers, and hermit thrushes, and occasional Swainson’s thrushes, ruby-crowned kinglets, and Pacific/winter wrens.
We turned up the Granite Creek trail, crossing deep, soft snow where an avalanche had brought down lots of broken branches. A group of mountain goats grazed in the slopes of Juneau Ridge. Marmots sunned themselves on the rocks, scurried across snow patches, and wandered into the underbrush.
Several tiny shrews scuttled across the path. We see them so often that there must be a lot of them! Shrews comprise an ancient group of mammals, originating perhaps forty-five million years ago. They live at an amazingly fast pace. Their little hearts beat 1200 times a minute! And they have to eat almost constantly, so they can never sleep for more than a few minutes at a time. They have very short lives (about a year), and the adults are reported to die after they reproduce.
Shrews eat a variety of invertebrates, including insects, spiders, and snails. They find their prey by echolocation (as do bats). Juvenile shrews have to learn to forage on their own, so growing up is a time of great experimentation for them. I recently learned something fascinating about young shrews: Although the rest of the skeleton is bony, much of the jaw initially remains as cartilage, which is flexible. The jaw bones harden gradually, in response to the bite force needed for capturing the commonest prey in the habitat of the young shrew: the muscle pull on the still-flexible jaws determines the proper bone formation for best use of the common prey. So if the young shrew eats mostly crunchy beetles and snails, the jaw develops one way, but if it eats squishy worms and caterpillars, the jaw develops another way. Shrews are unique among placental mammals in allowing the environment to shape skeletal growth.
Also wandering around in the trail were two very young deer mice, surely quite recently out of the nest. One of them took refuge under the raised toe of my friend’s boot—clearly, its mama hadn’t told it to beware of two-footed monsters! These two youngsters were in no hurry to hustle into the trailside vegetation, but scuttled aimlessly around in the trail, so we watched them for several minutes.
For no very good reason, we kept track of how many kinds of flowers were in bloom: over sixty species! And that doesn’t count the grasses and sedges, some of which are quite beautiful and worth knowing, but that’s a real skill that I lack.
The broad, white inflorescences of cow parsnip (a.k.a. Indian rhubarb) attracted many small insects. I fervently wished that I knew more about insects, because there was surely a story unfolding here. There were tiny brown beetles (much like those that pollinate skunk cabbage) and at least six kinds of ‘flies’ of various sizes, the smallest no longer than a millimeter. All of them crawled over the small flowers, sipping nectar and probably eating pollen. In their midst, there was often a wasp or two, also innocently nectaring, but occasionally leaping toward a fly. The flies took evasive action but sometimes the pouncing wasp was successful in nabbing its prey. Another variation of the old story about the wolf in sheep’s clothing.
As we passed Ebner Falls on the way down, we heard a rockfall rumbling downslope toward the creek, well behind us. But our curiosity didn’t extend to going back up to see the result—the horses were headed for the barn, and as we drove home, the little rains began again.