This article has been taken from “Wild California Vanishing Lands, Vanishing Wildlife Starker Leopold Tupper Ansel Blake” by “Raymond F. Dasmann”. California Deserts have unique ecosystems and habitats, a socio-cultural and historical “Old West” collection of legends, districts, and communities which is well discussed at “Tree Trimming Stockton CA“.
The desert often seems monotonous, gray, and vast. In the dry season (which is most of the time ), the traveler views mile upon mile of neatly spaced creosote bushes, with an occasional cluster of cactus or a stringer of desert willow along a dry wash. In the heat of midday, animal life is conspicuously absent. Coming suddenly upon a desert spring, then, is like finding an island in the ocean. The concentration of life is startling—the vegetation is a healthy green rather than gray, and there is a scurrying and fluttering of birds and small mammals.
Under a spreading mesquite, whose branches form an umbrella, a covey of Gambel quail may be found loafing. Their soft chirping is an expression of mutual reassurance that all is well. In the season of drought, the quail come daily to drink, and once there, they often linger through the day. Morning and evening the equal forage over the desert for distances up to half a mile, scratching in the sand for the seeds of weeds and wildflowers that fruited and died with the last rains. After the late feeding the birds return to the spring to seek safe roosts in the trees or tall shrubs, above reach of the prowling bobcat and under a leafy canopy that hides them from the hunting owl. The numbers of Gambel quail frequenting a spring may vary from a mere handful in dry years to hundreds in years of generous rainfall.
Wildflowers carpet the desert in wet years, and the quail browse on the tender leaves of the growing plants, which seem to contain some nutritive element that stimulates the urge to mate and nest. The males fight raucously over mates, and even after all the females are claimed, the excess males call persistently. In such a year of sexual enthusiasm, many young are reared, and, fortunately, the robust stands of annual plants scatter their seeds abundantly, so that there is adequate food to support the expanded quail population through the year.
Quite the opposite situation applies in a dry year. Wildflowers are stunted, and although the quail eat the fresh leaves, there are chemicals (steroids) that seem to suppress the mating urge rather than stimulate it. Under the worst conditions the quail do not even pair off and nest, but remain in winter coveys and conserve their strength for another year. Individuals die in one way or another and the flocks dwindle until, after several successive years of poor reproduction, a pitiful remnant of old birds persists. When at last another lush year comes, a big crop of young is raised, and quail are abundant once again. Boom and bust is the rule on the desert, and quail along with other life forms, reflect these oscillations. In bust years the desert spring is a crucial key to the continuity of many species, quail included. Without the spring, the remnants would never make it through protracted years of drought.
The welfare of desert rodents is similarly affected by the vagaries of weather. Abundant seeds that nurture quail after a good growing year are also the staff of life for ground squirrels, kangaroo rats, pocket mice, and other small mammals. Most desert rodents gather seeds when they are easily available and store them in underground caches for periods of scarcity. Such food storage is a form of insurance not available to quail. Another advantage is the ability or hibernation is accompanied by a drop in body temperature, sometimes approaching the ambient temperature of the burrow. In this manner the little mammal conserves food—both that stored in the body as fat and the seeds stored in the burrow. But all these ploys for survival of the individual do not of themselves stimulate the animals to reproduce. Just as in the case of the quail, nutritive elements produced in green leaves following adequate rain apparently stimulate sexual enthusiasm in desert rodents. Big litters of healthy young are the consequence. Jackrabbits respond in much the same way, and occasionally when some desert locality has been favored with good rains several years in a row, the jackrabbit population may increase to the point where highways become littered with bodies struck down by automobiles at night.
Boom years for the small vertebrates become, in turn, boom years for the desert predators. Hawks, owls, foxes, coyotes, and bobcats all respond to abundance of prey by successfully rearing more young of their own. Studies in a desert valley in Utah have shown a positive correlation between the population of jackrabbits and the number of coyote pups raised. Jackrabbits constituted well over half the diet of the breeding coyotes, small rodents being of less importance. Persistent coyote predation on jackrabbits was shown to reduce their numbers considerably in years of poor rabbit reproduction, and then coyote reproduction in turn would fall off. But in a boom year, jackrabbits raising four or five litters per season jumped numerically far ahead of their enemies, and it then became the turn of the coyote to catch up. This teeter-totter relationship between these two cohabitants of the desert has presumably continued for eons.
Larger animals associated with the desert waterhole are buffeted less by ephemeral changes in weather. Bighorn sheep and mule deer are long-lived compared to rabbits, rodents, and coyotes, and they have evolved techniques for outlasting periods of adversity. The waterhole is essential to their existence in hot, dry spells, but unlike quail or is essential to their existence in hot, dry spells, but unlike quail or coyotes, they do not have to drink every day. Even in hot summer weather, bighorns have been known to get along without drinking for periods of up to a week, which permits them to forage far from the waterhole. In such circumstances the animals return to the drinking place badly desiccated and may take on water up to 20 percent of body weight. Desert mule deer likewise can go for at least a couple of days without drinking. But water deprivation is not the normal choice of these animals. They prefer to drink daily if circumstances permit. Daily drinking, however, means that foraging must take place within a limited radius of the water source. When nearby food is exhausted, the foraging circle must be extended. If domestic animals such as sheep, cattle, or burros have access to the same spring, the depletion of food is greatly accelerated, to the decided disadvantage of the deer and the bighorns.