Sand dunes story

by Donna P. Bessken

WHICH ANIMALS LIVE HERE?

KANGAROO RAT

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.

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.

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.