If you stand at the overlook, you will see the Green River, Split
Mountain, and a rolling plain to the south that stretches to a hazy line
of mountains. To many, it is an unfamiliar land that lies strangely
subdued beneath a blazing sun and an intensely blue sky.
That blue sky is the key to the kinds of plants and animals that live in
this part of the monument. They live most of their lives under blue sky,
and, even when clouds do form over the mountains and drift across the
lowlands, the results are disappointing. A high wind, dust and sand, a
few drops of rain, and the storm is over.
The climatic conditions under which local plants and animals live are
conditions of extremes. On summer days the temperatures may rise above
100°, although the nights are usually cool. During the winter,
temperatures may skid to 30° below zero or more. It is not uncommon for
the thermometer to remain below zero for weeks on end. But the most
influential climatic factor is water—and there is little of it. The
total yearly precipitation is a little less than 8 inches! It is
interesting then to find such a wide variety of plants and animals that
not only survive but flourish under such rigorous conditions.
The methods used by plants in adapting to arid conditions are
interesting and varied. The wide-spreading, shallow root system and
thick stem of the cactus enhance collection and storage of water. These
strange plants are quite plump with stored water in the spring when the
snows melt, but they gradually lose this plumpness during the dry
summer, and by autumn many seem lifeless.
Other plants conserve their water by minimizing the loss through their
leaves. This may be done in a number of ways. The leaves of the spiny
greasewood are covered with a waxy substance that inhibits water loss
while the leaves of the sagebrush are covered with hairs or fuzz that
serve the same function. The leaves of the juniper are scale-like and
really don’t look like leaves at all. The most direct method of
preventing water loss through leaves is to drop the leaves themselves,
and this method is used to a greater or lesser degree by many desert
plants. The serviceberry is a good example of this method. In late
summer it looks dead, and yet the following spring finds it robed in
green and covered with flowers.
In contrast to the frugal habits of the plants just described, the
cottonwoods seem lavish indeed. Usually big trees, they spread a canopy
of green in whose shade rest birds and animals alike. Have you ever
rested under a cottonwood? If so, you will remember it as being cool
even on the hottest days. Part of the coolness was due to the hundreds
of gallons of water which are transpired through the leaves each day.
Because cottonwoods require so much water, they usually grow along
streams or near springs. Frequently they are seen along dry ravines
where their thirsty roots tap the subsurface drainage that lies hidden
below. Like the other plants however, when the supply of water becomes
inadequate they shed their leaves and wait for the next spring. Fast
growing, usually of large size, and wasteful of water where water is
dear, the cottonwood seldom lives two hundred years while the twisted
juniper on the dry, rocky ledge frequently lives as much as five
hundred.
[Illustration: SPLIT MOUNTAIN GORGE.]
Inconspicuous through most of the year are the flowering plants. Some of
these are annuals—plants that grow from seeds, mature, bloom, produce
seeds, and die in the span of a few short weeks. When the snows melt and
the sun warms the earth, the seeds that survived the winter germinate.
The usually barren hillsides produce spots of green that soon spread to
form patches as more and more plants mature. Lupine and locoweed are
purple and heliotrope splashes color along the roads, while the
fragrant, white, evening-primrose dots the sandy hillside. Scarlet gilia
and Indian paintbrush add a touch of red to the scene, and orange is
provided by the mallow.
April, May, and early June provide the best flower show as spring rains
supplement the moisture from melted snow. Their races won, their seeds
produced, the annuals wither and fade away as the temperatures rise. By
the first of July little remains of the splendid show.
Two plants do brighten the desert scene in August and September. Most
common is the rabbitbrush, a plant that grows almost everywhere. It is
rather inconspicuous except in late summer when its brilliant yellow
blossoms turn the whole shrub golden. The other is the bee plant of
which there are two species: one has yellow blossoms, and the other has
purple. These tall plants grow along washes, stream courses, roads, and
irrigation ditches. Their delicate blossoms are always surrounded by
insects drawn by the nectar the flowers produce in great quantities.
These, then, are a few of the typical plants. Each has adjusted its
needs to those limiting factors—winter cold, summer heat, and aridity. A
great number of plants grow on the monument that have not been mentioned
here, but they are like the typical plants and have similar ways of
meeting the problems of survival.
Many people who profess an interest in nature admit they cannot get very
excited about plants. Such disinterest may result in minimizing the
importance of plants in the general scheme of nature. That would be a
major error. The plants of the world are the foundation upon which other
forms of life are dependent. They alone are able to utilize the minerals
in the soil and convert carbon dioxide and water to carbohydrates.
Because of these abilities, the parade of life has been able to advance
only when the plants advance. In the present as in the past, the kinds
and abundance of plants set definite limits as to the species and
numbers of animals an area may support. Thus, if man changes the plants
of an area he will surely change the animals too, whether he realizes it
or not.
If you drive to the quarry in the heat of the day you will see only a
few of the birds that live here. They don’t like to hunt their food
during those hot hours. Frequently a turkey vulture sails majestically
above the plains along the Green River. Sometimes so high he appears to
be a speck, his telescopic eye searches the ground for the carrion upon
which he feeds. Another bird that does not mind the heat is Say’s
phoebe. He is usually found perched on a fence post, a wire, or a dead
branch waiting for some insect to buzz by. A graceful, short flight, a
pop of his beak, and then back to his perch to repeat the cycle again.
As he sits motionless, his gray breast and darker gray head and back
make him hard to see.
The time to watch birds is in the evening; as the sun sinks and the air
cools, they come forth. Small gray-brown rock wrens hop among the
boulders near the visitor center. Robins scurry through the leaves in
the stream course below the Dinosaur Quarry. Here too, western
flycatchers and Audubon’s warblers search among the cottonwoods for
insects. A flash of red and white is seen as a red-shafted flicker darts
from its nest in the hollow trunk of a tree. The sky is filled with
wheeling, twittering rough-winged swallows and white-throated swifts
that descend from their nests on the cliffs to feed upon the gnats and
other flying insects.
These are the birds that spend the spring and summer here. They raise
their families and, young and old alike, depart in autumn when frost
kills the insects upon which they feed. As they flee the cold of winter,
they are joined by many other birds that make their summer homes at
higher elevations or more northern latitudes. Ducks, geese, and swans
join the hordes moving southward. So do the various shore birds,
bluebirds, and hummingbirds.
But the sagebrush flats and brushy ravines are not left vacant by this
wholesale migration, for as the summer residents move out the winter
residents move in. The Oregon and gray-headed juncos spend the entire
winter here. Great flocks of mountain bluebirds descend from the
mountains and piñon jays make the hills resound with their screams.
Canada geese and golden-eye ducks live on the Green River and remain
until it freezes. The harsh croak of the raven is seldom heard in summer
but often in winter.
Few birds live here in winter and summer—the golden and bald eagles, the
red-tailed hawk, and the little sparrow hawk. Perhaps the most handsome
year-round resident is the magpie with its long, iridescent tail, black
and white body, and white patches on its wings. One other resident makes
his presence known by his eerie cry on frosty, moonlit nights—the
western horned owl. He hunts every night, summer and winter, but is
seldom seen. Occasionally he is disturbed upon his daylight roost and as
he skillfully dodges through the junipers, he makes a joke of the story
that owls don’t see well in daylight.
The mammals that live in the vicinity of the Dinosaur Quarry are almost
never seen. There are several reasons for this—almost all of them are
nocturnal, are very shy, and most of them are small.
In spite of their retiring habits, they reveal their presence in a
number of ways. Patches of bare earth under sagebrush and nearby sandy
slopes are crisscrossed with tiny paths beaten into the dust by deer
mice. Along the river bank, gnawed tree stumps, a few fresh chips, and
perhaps a webbed footprint tell us beaver have been active during the
night. The paired hind footprints of the kangaroo rat are common on the
hillside. Freshly fallen snow records the preceding night’s activities
in perfect detail.
[Illustration: GOLDEN-MANTLED GROUND SQUIRREL]
Were it not for the golden-mantled ground squirrels, our evidence of
mammals would be mostly indirect. But these little fellows are very much
in evidence all day long as they play around the visitor center and in
the picnic areas. They are handsome too, with their alert black eyes,
cinnamon neck and shoulders, and dark side patches with white stripes.
Most people call these ground squirrels chipmunks because both are
striped. Actually the two are easy to tell apart; the chipmunk’s stripes
run to the tip of its nose, but those of the golden-mantled ground
squirrel extend forward only to the shoulder region. Any small, striped
mammal seen near the quarry is probably a ground squirrel, as chipmunks
are rare here.
The water problem is an ever-present one for the mammals as well as the
plants. At first this may seem strange with the Green River so close and
several springs in the hills, but most of the smaller animals have very
restricted ranges. A deer mouse, for example, seldom travels more than
100 feet from his home burrow in his entire lifetime. The kangaroo rat
and the desert woodrat also have limited ranges although theirs are
somewhat larger than those of deer mice. The majority of such animals
must meet their water needs without springs and seeps. How do they do
it?
[Illustration: COYOTE. (COURTESY, U. S. FISH AND WILDLIFE SERVICE.)]
[Illustration: BADGER. (COURTESY, U. S. FISH AND WILDLIFE SERVICE.)]
The food they eat contains some water. The green vegetation of
springtime contains large amounts. Even air-dried foods such as seeds
contain some. And these animals don’t need much. Through the thousands
of years these little creatures have lived in arid lands, evolutionary
processes have altered their bodies and life patterns to fit the
conditions under which they must live. Surely one of the most useful and
interesting of their abilities is that of utilizing metabolic water.
Such water is obtained through oxidation of hydrogen contained in food
and is a by-product of metabolism. Putting it another way, during the
digestive process these animals are able to manufacture water from the
chemical constituents of their food and the oxygen in their blood. The
amount of water thus obtained is between 70 and 100 percent of the dry
weight of the food eaten. Thus some desert animals are able to live a
normal life span without ever taking a drink, and probably many of them
do.
Carnivores such as the badger and the coyote get some of their water
from the animals they eat and may go for days without visiting a spring.
But eventually they return to the river or a spring for a drink. This is
no special effort as carnivores generally range for miles in search of
prey.
Winter is a time of difficulty for most animals. Some of them like the
ground squirrels hibernate and sleep the winter away, but the majority
must rustle their “daily bread.” Winter storms drive the mule deer down
from the high country. Mice tunnel through the snow in search of food.
The white-tailed jackrabbit and the snowshoe hare change their coats
from brown to white. In particularly hard winters the animals die in
great numbers, first the weak and old, then the young, and sometimes
even animals in prime condition fail to survive.
The reptiles that make their homes in the Quarry Area of Dinosaur
National Monument are few in number. The rattlesnake is rare and seldom
seen. The only common snake is the bull or gopher snake. This snake can
appear very threatening as it swells its body and hisses loudly, but it
is not poisonous. Gopher snakes climb well and are often seen in trees
where they hunt for eggs and young birds.
Two lizards are commonly seen here during the summer. The side-blotched
lizard is about 1¾ to 2⅛ inches long with a somewhat longer tail. These
small brown lizards are frequently seen among the rocks near the parking
and picnic areas. The name, side-blotched lizard, is taken from the
black or bluish-black area behind the foreleg of the males. These
lizards are also called brown utas.
The western whiptail is also a very common lizard. As its name suggests,
it has a very long slender tail which it lashes from side to side as it
runs. This lizard is easily distinguished from the side-blotched lizard
by its larger size, longer more slender tail, and the presence of bars
and spots of black upon its back. In late summer, junior-sized young
whiptails appear, but their 3-inch total length is unimpressive compared
to 8-inch adults. The young are quite handsome with pleasing body colors
and bright-blue tails.
Often lizards are seen whose tails are missing. When the tail is pulled
or injured it can be shed by its owner. The shed tail may wriggle for
several minutes and attract the predator’s attention while the lizard
escapes. The tailless lizard soon grows another one that is usually
recognizable by its subdued or otherwise different color pattern.
Sometimes the broken tail does not fall off so it and the new tail form
a fork.
In summary then, we see that this apparently lifeless desert does
support a wide variety of living things and a great number of
individuals. Some of them, the plants and small animals, live here all
year round while others, such as most birds, live here only part of the
time. But whatever the length of stay, all living things must adapt
themselves to existing conditions at the time of their stay. If they
cannot adapt to static or changing conditions they must move or become
extinct.
Some 60 million years have passed since the dinosaurs ruled the world.
In that time mountains have risen, wasted away, and risen again.
Glaciers have come and gone. Many species of plants and animals evolved
and passed on to extinction. Every life form meets the test—adapt or
die. That test is as real to the dusty lizard basking on the quarry face
as it was to the dinosaurs whose bones you came to see.