To escape extermination, each species must in some manner foil its
enemies. Protective coloration is one of the more common adaptations
helping to do this. Most animals resemble their environment to some
extent. The conspicuous markings of some, like the bitter-tasting
monarch butterfly or the striped skunk, seem to function as a
warning to prospective predators that it is in their best interest
to look elsewhere for a meal.
Some animals, such as the white-tailed ptarmigan and the snowshoe
hare, have seasonal changes in plumage or pelage, wearing white in
winter and brown in summer. Even predators, such as longtail and
shorttail weasels, benefit from seasonal camouflage. Protective
coloration makes them less noticeable to prey species and to larger
predators.
Many insects, too, change coloration with the season. Bright green
grasshoppers of early summer become more brown with each molt,
matching the changes in the surrounding vegetation.
_Obliterative shading_ is especially important to animals that
frequent more than one habitat. Seen from above, turtles match their
dark background; from below, because of their lighter underbody
shading they blend into the bright skylight.
_Disruptive coloration_ aids in breaking up an animal’s outline.
Butterflies and moths commonly have disruptive wing markings. The
distinctive shapes of eyes can be concealed. Eye coloration may
mimic body color—as in the green katydid—or the eye may continue
disruptive body markings.
Ground-nesting birds are especially vulnerable to attack. Their eggs
tend to be heavily blotched with earthy colors, making them less
conspicuous. Chicks also carry these disruptive colorations on natal
down.
Most mammals, with coats of brown or gray, are inconspicuous when
motionless. Deer fawns are endowed with speckled coats, mimicking
the sun-flecked forest floor; this disruptive coloration, coupled
with absence of scent and their instinctive “freezing” behavior,
makes it difficult for predators to detect them.
The whitetail deer not only uses its white “flag” to warn others in
the herd of danger; it also allows a pursuing predator to use it as
a target. When the tail is suddenly dropped—abruptly obliterating
the bright white patch—the deer seems to disappear into its dim
surroundings.
Since overly conspicuous animals are prone to predation, natural
selection favors development of appropriate camouflage.
[Illustration: For such ground-dwelling birds as the white-tailed
ptarmigan, camouflage is an important survival adaptation. The
ptarmigan changes its plumage to match its surroundings: it is white
in winter, speckled in summer. Moving slowly and refraining from
flight, it is less likely than more-active birds to be detected by
sharp-eyed, motion-conscious predators.]
[Illustration: Birds that when hatched are covered with down and are
able to move about freely are called _precocial_. They are less
dependent upon their parents than are _altricial_ young, which are
naked and helpless when they hatch; but they must rely heavily on a
resemblance to their surroundings for survival during their first
flightless weeks. This spruce grouse chick, which blends into its
sunflecked forest-floor habitat, is an example of a precocial bird.]
[Illustration: The bold disruptive pattern of the killdeer chick’s
plumage helps this precocial bird avoid detection in its
open-prairie environment. This adaptation, coupled with the chick’s
instinct to freeze at the approach of danger, ensures that enough
young will survive to perpetuate the species.]
_Ursus arctos horribilus_: The Vulnerable King
At the apex of the food pyramid, this great beast is unquestionably
the king of Glacier’s biotic community. Yet the long-range future of
the grizzly bear is uncertain. With the grizzly exterminated from
most of its former range—which once extended into the midcontinent
and south into Mexico—its numbers have dwindled in proportion to its
diminished range. Present concentrations in the contiguous United
States remain in and around Yellowstone and Glacier National Parks.
Probably fewer than 200 of these magnificent creatures live in
Glacier National Park.
Grizzlies are easily distinguished from the more common black bear.
In addition to larger size and heavier build, grizzlies have a
characteristic shoulder hump; long, conspicuous claws; and a broad,
concave face that gives them a “dished-in” appearance. Fur is
usually brown; like the fur of the black bear, however, color may
range from black to yellowish. Light tipped hairs make the fur
appear frosted, giving rise to the nickname, “silvertip.”
Grizzlies, popularly considered arch predators, are more accurately
described as omnivores. Carrion, grasses, cow parsnip, and several
species of berries, bulbs, and tubers make up a grizzly’s diet,
along with insects, small mammals, and an occasional ungulate that
it can catch. As a result, grizzlies play several roles in the
biotic community, functioning as herbivore, scavenger, and predator.
Ranging widely in all life zones, grizzlies follow the spring
snowmelt up to the alpine meadows, returning to lower elevations to
hibernate from November until April. One to three cubs are born in
midwinter during hibernation. Since the maternal bond lasts two
years, a sow will accept a mate only every other year. Mortality of
subadults is high, resulting principally from competition among the
bears themselves. As with most animals, range—habitat—appears to be
the limiting factor of grizzly populations.
The grizzly is normally shy and fearful of man—but highly
unpredictable. Wounded or sick bears, sows defending cubs, young
adults, and bears that have become conditioned to human scent are
the most dangerous. As humans continue to encroach on grizzly
territory, odds of confrontation also increase. Recent fatalities
and personal injuries inflicted by grizzlies pose a vexing problem
to the National Park Service, which is charged with visitor safety
on the one hand and protection of the park’s remaining grizzly
population on the other. Continuing study of grizzly ecology and
increasingly enlightened bear management programs will, it is hoped,
allow man and bear to co-exist in a wilderness both require.
[Illustration: Grizzlies are fond of succulent spring grasses.]
[Illustration: Traversing all life zones in the park, the grizzly is
a true opportunist, eating anything from ants and berries to
wapiti.]
[Illustration: Seldom will a grizzly exceed 225 kilograms in
Glacier. This is a young adult.]