Protective Coloration
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 coloras in the green katydidor 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 inconspicious 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 droppedabruptly obliterating the
bright white patchthe deer seems to disappear into its dim
surroundings.
Since overly conspicuous animals are prone to predation, natural
selection favors development of appropriate camouflage.
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.
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
surroundingsfor survival during their first flightlessweeks.
This spruce grouse chick, which blends into its sunflecked forest-floor
habitat, is en example of a precocial bird.
The bold disruptive pattern of the kilideer 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.
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