[Illustration: KANGAROO RAT]
[Illustration: BURROW]
Guess which animal lives in which hole! How large is the entrance? The
size of the entrance suggests the size of the animal. How many other
openings are nearby? Often escape exits save rodents from predators. Are
there recent tracks nearby to indicate it is an active burrow, or is it
covered with sand and debris blown in by the wind?
Inside these burrows the temperature and living conditions are not as
extreme as those on the surface of the sand. Try digging a small hole in
the sand well away from bushes. How soon does the sand change as you
dig? Is it warmer or cooler or wetter? Beneath the surface the moderate
temperatures and increased moisture provide an escape from the intense
heat. Consequently, dune residents spend the day in their dens and are
active at night.
Kangaroo rats, for example, cannot tolerate heat and escape it by living
underground. Also they are active only at night. They are very efficient
water conservationists. Although water is essential to the kangaroo rat,
they rarely drink, but produce their own water from insects and dry
seeds they eat. They have no sweat glands, and excrete highly
concentrated wastes to minimize water loss.
These rodents are not related to kangaroos at all! Their name refers to
their hind legs which are highly developed for jumping.
Watch for their tracks—when a kangaroo rat is moving slowly, it drags
its tail which leaves a trail in the sand in conjunction with its foot
prints. When the rat moves quickly, its tail doesn’t drag. From clues
such as these we can determine whether the rat is running from a
predator or just leisurely looking for food. The entrances to their
burrows are about 4-5 in. (10-12 cm) in diameter and may be 3 ft. (1 m)
or more deep. Smaller rodents, such as pocket mice, have similar habits
but live in smaller burrows.
Lizards are more active during daylight hours. Even though they tolerate
higher temperatures than rodents, they would perish if they were
stranded in the open sun for an extended period of time. Notice how they
run from bush to bush, seeking the protective coolness as well as cover.
Lizards are cold-blooded animals, responding to temperatures around
them—cold, inactive—warm, active. In the winter months, there is very
little lizard activity. However, summer days with ground temperatures
reaching 200 degrees F. (92 degrees C.) or more are too hot for lizards,
and they must seek shelter. They eat plant material, insects and smaller
lizards, obtaining moisture from their food. They also conserve water by
excreting highly concentrated waste.
[Illustration: LIZARDS]
Perhaps least observed, but most inquired about dunes dweller, is the
sidewinder. Have you seen evidence of this rattlesnake today? It moves
in a sidewise manner leaving a series of parallel, J-shaped tracks in
the sand.
By looping across the sand, the sidewinder reduces slippage over the
loose material and decreases the amount of body surface in contact with
the hot sand. Sidewinders are primarily active at night, and escape the
heat of the day under a bush or buried in the sand, exposing only the
small horn-like structures on their heads. They eat kangaroo rats, mice
and lizards.
Imagine the dunes as an ocean where all the sand is water and plants are
islands scattered about. Each island offers shelter and a food supply
for the animals. Everytime an animal leaves the security of an island it
takes a risk. In daylight, people may play in the sand, but at night the
dunes come alive with the real business of survival. Usually all we see
of this activity the following morning is the evidence—tracks. Some
tracks are easily identified—each tells a story. Use the diagrams to
determine which animals most recently crossed the sea of sand around
you.
[Illustration: KIT FOX]
Coyotes come into the dunes for food. True opportunists, they eat
whatever is available—mice, kangaroo rats, rabbits, insects, mesquite
beans and many other things. Their tracks are difficult to distinguish
from those left by domestic dogs. Smaller dog-like tracks are left by
the kit fox. These small foxes have large ears and well padded feet.
They too feed on small rodents. Coyotes and kit foxes receive moisture
from their food and drink water at springs within their hunting range.
They avoid exposure to heat by being active at night and staying in dens
or shaded areas during the heat of the day.