Of Rock Rabbits and Water Shrews
by
Chris Maser


     If you could go back 25,000 years, you would find a world growing colder than that of today, the 5th of September 1247. As the world cooled, the Winters grew colder and longer while the Summers grew cooler and shorter. Over time, more snow was added than melted during the Summer, and the accumulating snow began to lose its light, fluffy texture. As the air was gradually forced from the settling snow, it slowly formed dense layers of granular ice crystals that, impelled by gravity, began to flow down the mountainside over the underlying bedrock. Because Winter storms regularly supplied more snow than melted during Summer, the glacier continued to grow and move.
     As the glacier flowed, it scooped up chunks of bedrock and carried them downslope, and it was the abrasive action of those chunks frozen into the glacier's base that ground down the underlying rock surface. Thus, the glacier sank ever deeper into the trench it was cutting for itself, polishing and smoothing some surfaces in its passing while gouging grooves and furrows into others.
     The glacier's quarrying action was aided by numerous fractures in the rock that formed prior to the glaciation and were enlarged by the action of frost. Existing fractures were pushed apart as the moisture entered them, where it froze and expanded, acting like a wedge. As the glacial ice moved over the surface, it pried away loosed pieces of rock and incorporated them into its base. The quarrying action of the glacier's base also facilitated water entering cracks in the rocks where, in freezing, it caused them to fragment in a way that the moving ice could exert its tremendous force. As the glacier moved, small stones and large boulders became embedded in the ice, were plucked from their places, and carried away. These rocks became the collective tool the glacier used to scrape out still other fragments from its bed.
     Although covered each Winter by new snow, the dirty ice deep within the glacier, now between 1,000 and 2,000 feet thick, was doing its work. Impregnated with sharp fragments of rock and grit, the blackened ice removed and transported large quantities of material, scouring the area as it bulldozed along its margins, undermining and steepening the rock walls. Over the decades and centuries, avalanches of rock fell on top of the glacier and add to their weight to its cutting power.
     The glacier did not move very far down the mountain, however, before the climate began to warm again. As Summers became warmer and longer, the snows of Winter melted more and more until the glacier retreated into its bowl-shaped cirque and then disappeared altogether, leaving its deposits, which ranged in size from a gray flourlike substance to boulders in what was to become the meadow.

     Thus, the fiery volcanism that built the mountains and the erosive power of wind, water, and ice that has worked to level them are some of the agents of the two opposing forces that together form the unity of Creation--the eternal becoming.
     Today, however, the 5th of September 1247, the cirque is bathed in sunlight, and the blue of the sky is reflected in the water of its small lake. Surrounding the lake, in the still-moist soil of the cirque's bowl, is a sparse carpet of vegetation in various shades of green and brown that earlier in the year sported the yellow of glacier lilies. The sides of the cirque have been somewhat softened in outline over the centuries by rocks of various sizes breaking off the steep sides and accumulating at the bottom in curved slopes called talus.
      Within the talus are small islands of finer material that passes for soil, which supports a meager variety of green plants, such as parsley fern, the succulent stone crop, and cinquefoil. Where the talus meets the meadow on the south side of the cirque, there is an abundance of herbaceous vegetation surrounding the base of the rocky rubble, and it is here that the rock rabbit or "pika" makes its home.
     If you were to sit quietly and listen and watch, you would soon hear the nasal  waaa, waaa, waaa, oink, waaa of a rock rabbit and then another as here and there they magically appear in the midst of sun-drenched boulders. The call is usually made from the top of a rock or from the doorway of a cavern between rocks. If you sit still long enough, you may hear a call run into a trill of alarm as a rabbit dives into the protection of the nearest crevice. And, occasionally, you will hear a faint call from deep within the rabbit's rocky fortress.

 

Stonecrop (left) and Cinquefoil (right).

     To see these wee creatures, who scamper silently and deftly over the roughest rocks on fur-cushioned feet, you must either catch the flicker of a movement out of the corner of your eye or be able to pick out the white margin of a small, round ear that is somehow out of place in this high, mountain world of jags and angles.

An observant pika

     An adult rock rabbit is about eight inches long, including its tiny, inconspicuous tail. Its broad, rounded ears, a little less than an inch in width, are blackish with a distinct white margin. The soles of its feet are covered with rather stiff, woolly hair, which gives it excellent traction on and silent running over the rocks of its home. The soft fur on the upper parts of its body is a uniform reddish brown that is slightly darkened over the back by black-tipped hairs, whereas the belly is tannish, and the throat is a clear reddish brown.
     These little denizens of the cirque find no terror in either the heat of Summer or the cold of Winter, for they keep cool deep in their rocky caverns during the hottest of days and warm in their snug nests under the deep snows during the coldest of nights. The rabbits are alert, keen of sight and hearing, and quick to dive into the depths of the talus at the first sign of danger.
     During the Summer and early Autumn, they can be seen between 4:30 and 10:00 o'clock in the morning and between 3:00 and 8:00 o'clock in the late afternoon and early evening, although some activity seems to be ongoing during all hours. Their nighttime activity, however, is confined to the safety of the talus and consists mostly of calling. Nighttime disturbances are instantly noted and immediately challenged vocally. During the breeding season, territorial calls are given on bright moonlit nights throughout the talus.
     When active in the open, they use lookout stations between their home areas and the meadow, where they gather vegetation to carry back to their particular portion of the talus. If you were to visit the talus in early June, you would see adult rabbits engage in gathering vegetation from the meadow and transporting it to their own territories within the talus, where they store it under the protective cover of the boulders. This activity, called "haying," continues until the beginning of November, unless a heavy, early snow makes the vegetation of the meadow temporarily inaccessible.
     During haying, rock rabbits carry one mouth-full of vegetation after another from the meadow to their home area and store it in piles deep within the talus. Among their foods, which include grasses, herbs, and shrubs, subalpine lupine is especially favored. An individual's storage area often forms a complex of hay piles, some of which may grow so large that they eventually spill out of the internal confines of the talus and become visible in the openings among the boulders. Although rock rabbits usually store more hay then they need in a given Winter, they do not use the same storage areas every year. Their social organization is, nevertheless, centered around their hay piles.
     During the haying season, they spend much time in gathering food. One adult male, during this golden September day, makes 130 trips to the meadow to feed. His eating is rabbit-like in that a large leaf is seized at the tip and drawn into his mouth with rapid chewing motions without the assistance of his forefeet. In addition to feeding, he makes just over 200 trips to gather vegetation for his hay pile during the sun's trip across the heavens.
     His trips to the meadow are periodically interrupted, however, by chasing other rabbits for trespassing in his territory, being chased for trespassing in another's territory, calling, periods of observation, grooming, and heeding predator alerts sounded by rabbits elsewhere in the talus. In turn, he defends his own specific area against the trespass of others by vocalizing, consistent spacing his hay piles, chasing trespassers, fighting, and marking his territory by rubbing secretions on strategic rocks from well-developed chin glands.
     In Winter, where the snow drifts to depths of eight feet or more around the edge of the talus, rock rabbits dig tunnels into the snow from about two feet below its surface down to the buried vegetation of the meadow. By Spring, the vegetation will be severely grazed immediately adjacent to the talus, but only where the protective cover of the snow is sufficient to give the rabbits a sense of security.
     During the Winter, the rabbits' piles of droppings and their sites of urination, which turn whitish with continual use, mark the openings of the tunnels they use to gain access to the surface of the snow. Sometimes their activity results in accumulations of droppings in tunnels, called fecal towers.
     March brings to onset of reproductive activities, which peak during May, June, and July, and are largely over by the end of August. The beginning of the breeding season is announced by the long territorial calls of the males and the short, answering calls of the females. Although breeding males visit females in adjacent territories, they tolerate one another only during the mating season and again practice mutual intolerance soon after the youngsters emerge from the inner protection of the talus. Litters range from one to six young, but two to three is the norm. The gestation period is about 30 days, and there may be two litters per year.
     Young rock rabbits begin to appear on the surface of the talus by the end of June, and display their first territorial behavior with high-pitched calls about a week after they emerge. Within two weeks, the calls of the young are indistinguishable from those of the adults. The adults become intolerant of their young soon after the youngsters become independent of parental care.
     The young lack alertness when they first emerge from the talus, and are therefore vulnerable to predators, such as marten and red fox. Because both marten and fox are too large to follow the rabbits into their talus, experienced rabbits keep marten and fox in view when either approaches the talus and warn one another, even at the expense of being seen by the predator.
     The rock rabbits' main predators are short-tailed and long-tailed weasels, both of which can penetrate the rocky fortress and either kill the adults or carry off whole litters of young from their nests. For their part, rock rabbits are markedly silent when a weasel is near, because, with its snakelike body, a weasel can follow a rabbit anywhere, leaving little chance of escaping the sharp, needlelike fangs and deadly jaws.
     But for now, the late afternoon sun is approaching the western horizon, and haying is in full progress. Here and there a rabbit calls from the talus, then another, and another. It is a quiet afternoon with clear, blue skies and light breezes that dance and whirl over the meadow on their way to the talus and the small lake in the cirque, rustling the dead stalks of Summer's grasses in their passing. The breezes skip and skitter over the surface of the water, ruffling it as they dart back again to the meadow along the stream flowing out of the cirque.

 

The stream leaving the cirque above the meadow. Note the beginning of vegetation along its edges. (left) The stream after reaching the meadow (right).

     Presently, a tiny spider climbs up a tall stalk of grass in the meadow and raises the rear of its body in the air, almost standing on its head. From the tip of its abdomen, it ejects a mass of silken threads from its spinnerets into the breeze that is causing the grasses to sway. Suddenly, without visible warning, the spider is jerked off its stalk of grass and is born skyward to join other spiders riding the warm, afternoon wind flowing up the mountainside from the valley of the big river and beyond.
     If you could ride the wind with the spider on its gossamer balloon high above the meadow and you were to look down, you would see the stony brow of the small cirque carved out of the mountain's spine above and to the east of the meadow during the last great ice age. In fact, it is the waters draining from the snow-melt lake in the saucer of the cirque that fills the small stream and sub-irrigates the meadow, now in hues of gold and amber as Summer's flowers and grasses pass into Autumn's harvest. To the north and to the south, along the sides of the meadow, and to the west, below the meadow as far as you can see is a forest of variable age in corresponding shades of green--the younger the forest the brighter the green.
     If, however, you had been here around 10,000 years ago, you would have seen the last of the dirty, melting ice of the once-dominant glacier as it completed its transformation under the warming Summer sun, rising skyward as vapor to join the clouds and flowing westward as water in streams and rivers to join the sea. You would have seen the debris--boulders, rocks, pebbles, sand, and fine flourlike material, collectively called glacial till--spread several feet thick over what is now the meadow.
     Water from the melting ice, having carved several small stream courses through the debris over the decades and centuries, gradually became a single stream flowing from the cirque, until the glacier, vanquished at last by the sun, gave up in total retreat. Thus beginning and ending in the same place, a place now greatly and forever changed, the glacier, as sculptor, passed into time, into the ever-fading light of history.
     Time passed and the seeds of plants, some riding winds from distant places, parachuted out of the sky; others, riding attached to the hair of deer and elk and to the hair of their predators, pumas and wolves, fell onto the stony soil. Although most seeds were eaten by small rodents or passing birds, some survived to germinate and grow. Again, most were eaten, and again some survived to maturity and shed their seeds. Each year more and more seeds were sown, and decade after decade, century after century, the stony surface gradually became clothed in the pioneering grasses and herbs whose living and dying built and nourished the soil that today supports the grasses and flowers that sway and nod in the meadow. In time, the many streams became combined to the one stream.
     Where the stream leaves the lake and begins flowing through the meadow, is a small waterfall made by two large, flattened boulders whose upper surfaces appear at first glance to be polished. On closer inspection, however, they are seen to be covered with fine striations, evidence of the glacier's millennial march toward the valley below--really more of a millennial marching-in-place. Under the boulders, behind the waterfall, is a small, protected hollow with a gravel bar that slopes into the cold, clear water.
     The damp gravel takes on a dull luster as the setting sun penetrates the veil of cascading water. The streamsides leading into the hollow are protected along the water's edge by the overhanging banks with their rank growth of meadow vegetation, which has developed well past the pioneering herb stage into a willow/sedge community whose strong, intertwining roots hold the soil firmly in place along the banks.

 

     Note the small gravel bar that was created by the faster, higher waters of Spring, as well as the dark areas, where the higher water under-cut the bank. (left) The slower, lower waters of Summer sometimes disappear belowground, where they "sub-irrigate the meadow vegetation (right).

     As the sun's light begins to fade from the pebbles, there is a sudden bustle of activity. Two northern water shrews race over the gravel bar amid much shrill squeaking. And just as suddenly as they appeared, they disappear into the water.
     The northern water shrew is the second largest of the long-tailed shrews in North America. It is exceeded in size only by the marsh shrew that lives in the marshy areas at the lower elevations in the forest and along the big river in the valley bottom. The northern water shrew is about six inches long, of which about half is tail. It has a long, pointed, flexible nose; minute eyes; and short, wide, round ears that are almost concealed in the fur.
     The fur itself is dense, soft, and velvety. The upper parts are dark gray to blackish, lightly frosted with paler hairs. The underparts, from the throat to the base of the tail, are whitish tinged with gray or brown. The tail is blackish above and whitish below.
     Water shrews have fringes of short, stiff, silvery hairs (almost like bristles) on the margins of their feet, including the toes. The fringe, usually called a swimming fringe, is most noticeable on young animals. It appears to sustain much wear during a shrew's life and is not replaced by new hair in an old animal. Adults weigh up to half an ounce.
     At this moment, however, daylight continues to glide silently westward with the setting sun. The fading light is replaced in the eastern sky by the dark line of night--an arched curtain pulled across the great vault of the heavens as the stars begin to twinkle and the planets to stare at the small, spinning sphere called Earth.

     Lewis' monkey flower growing in one of the meadow's streams, where it will soon be shrouded in darkness, then bathed in the gentle light of the moon before seeing the sun rise again.

     As the sun sets, the silvery edge of the full moon begins to show over the cirque's stony brow. The rising moon floods the meadow with its soft glow, casting shadows behind boulders and behind deer and elk feeding on the lush vegetation. The moon, reflecting the light of the sun, is a symbol of both day and night, of light and darkness, of heat and cold. Its gentle light shrouds the meadow in the mystery of the half-seen, the shadowy silhouettes of what is and what might be.
     Where the stream slows, deepens, and meanders in the flatter, more level portion of the meadow, the water flows from the darkness of the banks' shadows into the mercurial light of the moon, gliding like quicksilver from shadow to shadow. If you were to sit motionlessly on the bank of the stream, you would soon see the small, dark form of a water shrew appear from the shadows only to dive beneath the surface of the water in search of food.
     The water shrew is the most skilled swimmer in these swift, cold, mountain streams. Its fur is so thick and soft that it traps and holds air, which allows the shrew to sit on the surface of the water and float like a duck.
     Because the shrew's fur gives it such buoyancy, it must force its way to the bottom of the stream, where it literally stands on its long, flexible nose, searching the bottom for food, its hind feet kicking rapidly to maintain this position. To change direction, it twists its body, and to come to the surface, it simply stops kicking and rises like a cork, bursting to the surface with dry fur.
     Wherever the shrew goes under water, it is trailed by a row of bubbles rising out of its fur. In fact, the shining layer of air that clings to the surface of its fur as it swims makes the shrew resemble a silvery fish.
     Although a water shrew's fur is remarkably resistant to wetting, water does begin to penetrate after several minutes of aquatic activity. Therefore, a shrew leaves the water and dries its fur by rapidly and thoroughly working over its body with its hind feet. During this process, which lasts from 10 to 30 seconds, fine droplets of water are thrown off. The stiff hairs of the swimming fringe along the margins of the hind feet, functioning almost as a comb, facilitating drying the fur.
     One shrew, startled by the sudden appearance of a water vole, which is really a semiaquatic "meadow mouse," darts out of the shadow of the stream's bank and runs across the surface of the water only to disappear in the shadow of the opposite bank. The stiff hairs of the swimming fringe trap air that allows the shrew to literally walk or run on the surface of the water. In short, the northern water shrew is a truly remarkable mammal; it can swim, dive, float like a duck, and walk both on the surface of the water and on land.
     Water shrews feed mainly on invertebrates, such as the larvae of aquatic insects, earthworms, slugs, and the larvae of terrestrial insects found along the edge of the meadow by the stream. In addition, the shrews catch and eat such vertebrates as small trout and sculpins, as well as larvae of the Pacific giant salamander, provided they are less than three inches long.
     When hunting fish and salamander larvae, a shrew dives to the bottom and, finding its prey, bites it somewhere around the head, which seems to paralyze it. The shrew then pops to the surface and swims to a preselected site, gripping the fish or salamander larva by the head while its body trails alongside that of the swimming shrew. Once out of the water, the shrew bites its prey through the head with its front (incisor) teeth to kill it.
     When hunting recently hatched trout, called fry, in the shallow water of the stream's edge, a shrew rushes about the rocks, stopping frequently to elevate its flexible nose as if trying to detect a scent. It then plunges into the water and swims beneath the surface. If the trout fry are not moving, the shrew has difficulty finding them and frequently bumps into them seemingly by accident, but if the fish are swimming, the shrew has little difficulty in finding and following them. When hunting is good, a shrew will catch more than one fish, carry it to the chosen spot, kill it, and store it for later use, which is important because a water shrew may eat more that its own weight within a 24-hour period.
     Although water shrews are primarily active at night, they may be abroad at any time during the 24-hour cycle. Their activity is intermittent and only for short periods. After a period of activity, a shrew may retire to its spherical nest, constructed out of moss or other vegetation, or it may simply stop and fall asleep in some safe place in a crouched position. Occasionally, a shrew, going to sleep on a rock under the protection of the overhanging bank along the stream's edge, loses its balance and falls into the water--a rude awakening!
     Male water shrews born in the late Spring and Summer do not become sexually active until the December or January following their birth, and reproductive activity then continues until August. Females are either pregnant or raising young from February until August, and may produce several litters during the breeding season. Litters normally range from five to eight young, but six is most common.
     Water shrews are active throughout the year, and in Winter, as in Summer, their major activity is confined to the banks of the stream. The stream does not freeze solid under the insulating cover of snow, although a small shelf of ice forms along its banks and, in some places, across the entire stream. As the top of the lake in the cirque freezes, the level of the water along the stream drops, forming a space between the bottom of the ice shelf and the water's surface, which becomes the Winter domain of many a water shrew.
     But for now, the shrews are bathed in the quiet light of the September moon as they alternately swim and dive and float along the stream through the meadow.

I tell you this story in memory of and in tribute to my friend and mentor, Murray L. Johnson, with whom I shared the study of mammals for many wonderful years.


Murray L. Johnson

Murray L. Johnson Murray L. Johnson











Murray and his wife, Sherry.


© chris maser 2004. All rights reserved.

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