The most frequently seen mammals in the monument are rodents and members
of the hare clan. Among the latter group are two rabbits. The DESERT
COTTONTAIL is common in the lower levels of the desert, and the EASTERN
COTTONTAIL inhabits the mountains to 8,600 feet. Adaptable to a wide
range of environmental conditions, these animals augment the water they
obtain from springs with moisture derived from sap. There are two
species of JACKRABBITS (actually hares) in the monument. They remain at
the lower levels, where they are a common sight amid the cactuses.
Unlike rabbits, which are born naked, blind, and helpless, hares are
born with fur, open eyes, and the ability to move about.
[Illustration: The Yuma (or gray-tailed) antelope ground squirrel, a
chipmunk-like rodent of the desert and grassland.]
[Illustration: In the monument, the cliff chipmunk prefers the
oak-pine woodland and the coniferous forest.]
Among the monument rodents the largest are the PORCUPINES. Though rarely
seen, they leave characteristic scars on pinyons and ponderosa pines,
recording their feeding habits at higher elevations. They are also
active in the chaparral belt, and an individual occasionally wanders
down into the desert where it eats mesquite beans and samples the bark
of ocotillos and other shrubs and trees.
Several species of ground squirrels are abundant. At the lower levels,
especially among creosotebushes, the ROUNDTAIL GROUND SQUIRREL finds
suitable living conditions, while the YUMA ANTELOPE GROUND SQUIRREL
ranges from the cactus forests into grassland. At this elevation and
upward through the pinyons and junipers, the ROCK SQUIRREL makes its
burrows in rocky ledges and brushy canyons. CLIFF CHIPMUNKS enliven the
oak-pine woodland and higher forests with their quick movements and
cheerful chatter.
KANGAROO RATS honeycomb the soil from the cactus forests up to the
oak-pine belt. Remaining underground during the day, they are frequently
seen at night. These animals do not require free water; they obtain
adequate moisture from a chemical process within the body during the
digestion of food, which is mostly dry seeds. WOODRATS, famous in song
and story as pack rats or trade rats because of their habit of carrying
away objects of human use and leaving something else in their place, are
found throughout the monument at all elevations. Look for their stick
nests among the pads of prickly pear, a favorite food.
Other rodents common in the monument include the CACTUS MOUSE,
GRASSHOPPER MOUSE, DEER MOUSE, and VALLEY POCKET GOPHER.
[Illustration: The four species of kangaroo rats found in Saguaro
look too much alike to be distinguished in the field.]
[Illustration: Mule deer.]
Among the larger mammals in the monument are two species of deer. The
MULE DEER subsists in winter on cactus fruits, ephemerals, and other
desert vegetation. In summer they find abundant browse in the higher oak
woodland. The forested areas along the crest of the Rincons support a
population of the smaller WHITETAIL DEER. These graceful animals browse
on aspen, buckbrush, and other shrubs and small trees. They are
particularly fond of acorns. When snow flies some descend to the
protective cover of the oak-pine woodlands and chaparral.
PECCARIES, characteristic of southwestern deserts, usually travel in
herds of from three to as many as 50 animals. They wander through the
groves of mesquite along desert washes, and root among beds of
pricklypear. Pricklypear pads are their chief food; they are said to
feed upon cactus fruits in summer and autumn. In addition to the
moisture obtained from succulent stems and fruits, peccaries require
considerable water, hence they frequent springs and seeps. Small bands
of these animals occasionally visit the waterhole near the visitor
center, where they are excitedly watched by visitors fortunate enough to
be in the lobby at the time.
Saguaro National Monument also has a large number of predatory animals.
Many of these, popularly believed to be exclusively meat-eaters,
actually also eat much vegetable matter. The predators—an exciting part
of the monument’s fauna—play an important role in preventing
overpopulation of the prolific rodents.
Chief among predators is the COYOTE, which ranges throughout the
monument. In winter, coyotes are found principally below 6,000 feet,
where hunting is easier and where rodents remain longer out of
hibernation. They are also known to roam the forested heights of the
Rincons and Tanque Verde Ridge. Studies of coyotes in the monument made
by biologist Lowell Sumner in January 1951 showed that their winter diet
consisted of about 78 percent fruits and seeds, 11 percent small
rodents, 7 percent deer, 4 percent birds, reptiles, insects, and
carrion, and 1 percent debris. The coyote is one of the principal wild
creatures associated with the history of the West, and its continuing
presence in the monument brings a thrill of pleasure to visitors who
hear the voices of the pack during the calm of evening, or catch a
glimpse of one of these gray canines trotting through open stands of
saguaros. BOBCATS, ranging over much the same territory as coyotes,
subsist principally on rodents, birds, and insects. Because of their
secretive habits, they are seldom seen.
[Illustration: Collared peccary, or javelina.]
The GRAY FOX is another fairly common inhabitant of the cactus desert
and higher brushlands, and is also known to roam the forested uplands.
It is usually seen at night. Rodents are its principal source of food,
but it also preys on birds and reptiles and eats much vegetable matter.
The smaller and rather rare KIT FOX, restricted mostly to the desert, is
also a night hunter. Kangaroo rats are a favorite item in the kit fox
diet, but these small predators also eat grasshoppers and other insects.
Skunks, members of the weasel family, are relatively common in the
monument, and several species inhabit areas where water is available.
They are usually active at night. The HOGNOSE SKUNK is a desert dweller
recognizable by its solid-white back. It roots for insect larvae and
eats cactus fruits, bird eggs, and nestlings. The STRIPED SKUNK ranges
throughout the monument; the SPOTTED SKUNK is found at all elevations,
usually among rocks. Insects, rodents, and fruits are its main food.
Another member of the weasel family, the BADGER, is occasionally seen in
the desert although it is by no means limited to that habitat. The
badger feeds mainly on rodents, which it digs from burrows with its
strong forelegs and heavy claws.
The RACCOON, longer-legged than the badger, is readily recognized by its
gray fur, black mask, and ambling gait. It inhabits brushy canyons
having permanent water, and sometimes wanders up into the pine belt in
summer. Amphibians, scarce as they are, and other water creatures are
among the preferred foods of raccoons; but they also eat small rodents
and plant food, including berries, acorns, and other fruits.
[Illustration: Badger.]
The RINGTAIL, a smaller relative of the raccoon, is somewhat similar in
habitat preference and nocturnal habits. Its flattened, bushy tail,
acting as a balancer, helps this short-legged, agile animal in leaping
from point to point on the steep rocky surfaces it seems to favor. It
sometimes takes up residence in little-used or abandoned buildings,
where small rodents, its principal source of food, are usually abundant.
About the size of a house cat, it has large eyes and ears and
alternating dark and light bands on its tail.
A tropical animal that seems to be extending its range northward, the
COATI (or coatimundi) is often seen in the forests of the Rincons. With
long snout and long, banded tail, it looks something like an elongated
raccoon, to which it too is related. These omnivorous animals travel in
bands, rooting among leaves for insects and whatever else they can find.
[Illustration: Coati, or coatimundi.]
[Illustration: Desert vegetation near Red Hill, Tucson Mountain
Section.]
the rhythms of nature
Natural landscapes may appear unchanging, but this is illusion. Within
the apparent constancy, daily and seasonal cycles, fluctuations in
numbers, and long-term change are the rule.
Daily cycles are obvious to those who are about at the edges of the day.
Take 24 summer hours in the cactus forest of Saguaro National Monument.
When the first light comes over the mountains, curve-billed thrashers
and cactus wrens sing noisily among the chollas. Other birds soon join
in. The early morning walker is likely to hear peccaries grunting in the
mesquites along a wash, or see mule deer staring at him, frozen like
statues before sudden flight to a sheltering thicket.
At midday, the scene is quiet. Nothing stirs under the baking sun except
perhaps a vulture, soaring on the hot air currents. The desert creatures
have not gone—they are in the shade of bushes or underground. Even some
of the plants are “taking a siesta,” having folded their leaves or
closed their leaf pores.
Soon after sundown the desert comes to life again. The birds give a
subdued version of their morning’s vocal performance. Tarantulas begin
their slow, stately walk over the ground searching for prey or mates.
Coyotes stretch and howl—a prelude to the evening’s hunt. As night
falls, rattlesnakes emerge from their cool retreats to search out
kangaroo rats, which in great numbers are scrutinizing the sand for
seeds. And through the night, creatures of many other kinds hunt food to
last them through another broiling day.
The rhythmic patterns of the daily cycle are paralleled on a larger
scale through the year—seasons of activity follow seasons of quiet. In
the desert, rain or lack of rain marks the changes, though gradually
rising or falling temperature adds its impact.
The gentle rains of winter prepare the way for the year’s greatest burst
of activity. By March, spring flowers are blooming and birds are
starting to nest. Snakes begin to come out of hibernation. April and May
see the apex of spring activity, as insects swarm around the flowering
plants, and birds take advantage of this proliferation of food to raise
their young. The desert now is yellow with the blossoms of paloverde,
mesquite, acacia, and brittlebush.
But April also marks the beginning of a drought that intensifies through
May and June, making these last 2 months the year’s parching crucible in
which reproductive ability is tested. If winter rains have been meager,
the heat and drought of May and June can kill all the young of many
birds. Some birds, such as Gambel’s quail, may not even attempt to nest
in a dry year. Conditions may be so harsh at this season that some
mammals, such as the pocket mouse, close up shop completely, sleeping
the days away underground.
Relief comes with the rains of July and August. Now the summer annuals
spring magically from the ground, perennials put forth new leaves, and
saguaros do all their growing for the year. This summer burst of plant
growth is accompanied by a new hatching of insects, which allows a few
more birds to nest, and along with the new vegetation supports a larger
pyramid of animal life generally. Among the new animals that reappear
are toads, which now emerge from their long sleep in the soil to mate
and lay eggs in the pools formed by summer rains.
When the last torrential rain of August or September falls, a new dip in
the yearly cycle of activity begins. This one is not so deep, not so
trying, as the drought of early summer, but it too is a time of relative
quiet. Roundtail squirrels go underground to sleep until cooler weather
comes. Now the migrating birds slip through, hardly noticed among the
mesquites and paloverdes. Butterflies lay their eggs, in preparation for
a new generation beyond the winter. Signaling the last phase in the
yearly cycle, wet canyons turn yellow and brown as cottonwoods, willows,
and sycamores present a pale version of the spectacular foliage displays
seen in the East.
While these daily and seasonal cycles are following their well-known
courses, each species of plant and animal is undergoing its own
fluctuations, in a constant struggle that generally goes unnoticed. For
the balance of nature is not a static one, but more like the rocking of
a seesaw on its fulcrum. The population of a species goes up one year,
down another—depending on the weather, the food supply, predators,
competitors, and a thousand interactions that reverberate through the
community in which it lives. The numbers of some species, like the
Gambel’s quail, fluctuate wildly from year to year, while those of
others, such as the harvester ant, remain quite stable. But the
oscillations of the seesaw, big and little, average out from year to
year so that the species maintains itself in the community. The other
members are going through the same thing, in a system of checks and
balances that over the short run keeps the whole community nearly
constant.
But over decades, centuries, or longer, the fulcrum of the seesaw moves:
the larger environment changes, and the community and its constituent
plants and animals must change with it or perish. Such changes may be
climatic, as we saw with the formation of the Southwestern deserts; or
it may be geologic, as with the rising and partial disintegration of the
Rincon Mountains. The efforts of plant and animal species to meet such
changes constitute in large part the story of evolution, for new
environments spawn newly evolved forms of life. Evidence of such
evolution we have seen in the plants of the Sonoran Desert, notably the
giant saguaro cactus, whose prickly ancestor lived in the West Indies
only 20,000 years ago.
Thus nature is ever-changing; and the inexorable rule for all living
things is, “adapt or perish.” Before technological man enters the scene,
the slow evolutionary process can keep pace with the changing
environments, though here and there a species is dropped by the wayside.
Generally, communities of living things reach new equilibria without
serious disruption.
But what happens when man, with his machines and his passion for
progress, institutes changes of a speed and kind and on a scale
drastically different from those brought about by earthquakes, storms,
shifting climates, and other natural phenomena? What happens to the
living things that have adapted to the harsh desert environment when
that environment is drastically altered?
[Illustration: Saguaro cactus being uprooted.]
the impact of man
Man has been a part of the scene in this region for several thousand
years, but until recent times his influence on it was minimal. Only with
the rapid technological development of the last century has man been
able to make a major impact on this landscape. Thus the story of man,
here as elsewhere, is a story of gradually accelerating power to change
environments, a power that now threatens to destroy environments, and
with them, man himself.
From carbon-14 dating in Ventana Cave, we know that man was here at
least 12,500 years ago, in the Pleistocene age, a time that was cool and
moist compared to the present. Living by hunting, he followed mammoths
and other large mammals. As the climate warmed during succeeding
millenniums, and these mammals became extinct, he came to rely more on
plant foods. These hunters and gatherers necessarily had to live in
small bands scattered over the land, since the plants and animals on
which they depended were widely dispersed. By 300 B.C., they had learned
from people to the south how to cultivate food plants, and had developed
a sedentary way of life. About 2,300 years ago a group we call the
Hohokam settled in the Salt and Gila River basins (including the Santa
Cruz Valley). By A.D. 700 they had a well developed agricultural economy
including extensive irrigation systems. Pottery fragments, projectile
points, petroglyphs (rock carvings), and other evidence show that
Hohokam villages existed for about 600 years in the eastern section of
the monument along Rincon Creek and its tributary washes. Archeological
work in the Tucson Mountain Section has indicated that this area was
visited only temporarily by the Hohokam, for hunting, food gathering,
and perhaps ceremonial purposes.
During the 15th century the Hohokam high culture vanished. Soils made
salty from irrigation water and internecine warfare are suggested
explanations.
When the Spanish explorer Coronado passed to the east of the Rincons in
1540, he found the Sobaipuri living there. The Pimas, descendants of the
Hohokam, occupied the same basins the Hohokam had. To the west, in drier
country, lived the Papago. These tribes, thought to be descendants of
the Hohokam, lived much the same sort of life, practicing irrigation
where surface water was available, hunting and gathering where it was
not.
The period of Spanish rule, implemented by a series of missions, began
in the Santa Cruz Valley about 1692, when the energetic Father Kino
began his work among the Pima and Papago. The mission system
concentrated the Indians in fewer places, brought Spanish and, later,
Mexican settlers into southern Arizona, and introduced sheep, cattle,
and goats. Although the new culture must have had some environmental
effects, there is no evidence of drastic change. Grass was plentiful,
and streams, including the Santa Cruz, remained marshy and unchanneled.
After the Gadsden Purchase of 1853-54, however, when the present
boundary with Mexico was established and this area came into United
States ownership, man’s impact on the land increased. Apache raiding had
been a deterrent to settlement during the 18th and 19th centuries, but,
after the Civil War, American soldiers got the upper hand and settlement
increased. Following completion of the Southern Pacific Railroad to
Tucson in 1879, a cattle boom began. The disastrous results of the
livestock explosion of the eighties—overgrazing, soil erosion, and
starvation of cattle—we have already seen in the story of the saguaro
cactus. In 1890, a flood cut a deep channel in the Santa Cruz River,
transforming it from a meandering, marshy stream to the usually dry
incision one sees today. The arroyo cutting of this and many other
rivers throughout the Southwest was undoubtedly due partly to increasing
aridity, which reduced the plant cover and its water-holding capacity.
But the erosion was probably triggered by overgrazing.
In the monument, we have already seen how grazing pressure, hunting, and
predator control reduced ground cover and led to an upsurge of certain
rodents and a decline in large mammals. But there have been other
man-induced changes. For as long as there has been forest on top of the
Rincons, there has been fire. Lightning-caused fire is a natural part of
ponderosa-pine forest, every few years burning the litter and small
trees and shrubs from the forest floor, and thus maintaining open stands
of tall trees. But since 1908, when the Rincon Mountains came under
protection of the Forest Service, U.S. Department of Agriculture (to be
followed in 1933 by National Park Service, U.S. Department of the
Interior protection), fires have been put out as fast as possible. This
policy has resulted in a paradox. On the one hand, thickets of scrawny
young pines and shrubs such as buckbrush have developed in many places
under the tall pines. On the other hand, the accumulation of litter and
low-level vegetation has provided fuel over the years for occasional
very hot crown fires, which have been hard to control and which have
burned large acreages. On top of the Rincons you can see several meadows
that resulted from these fires. Only a few scattered trees and stumps
remain in them to suggest the forest that once was there.
Ideally, national parks and monuments should be “vignettes of primitive
America”—naturally evolved landscapes in much the same condition as when
first seen by Europeans. In reality they are compromises—beautiful,
wild, but still bearing the marks of human occupation. In Saguaro, as we
have seen, fire control has produced a forest different from that known
to the Indians who once lived here; grazing has depleted the ground
cover; and hunting has removed the desert bighorn from its rocky haunts.
In these days of burgeoning population, when human influence is
affecting every natural landscape, environmental management becomes
necessary to approach the ideal of naturalness. This may mean
“prescribed burns” to return forests to their earlier state; elimination
of grazing; or reintroduction of animals once native to a park. In the
summer of 1971, after 2 inches of rainfall, natural burns (caused by
lightning strikes) were allowed to run their courses.
Some or all of these measures may be taken in Saguaro, in order that
future generations will know a piece of the Sonoran Desert as it was in
Coronado’s time.
The realization of this goal, however diligently we work toward it,
seems almost each day to become more difficult of attainment. These
desert and mountain environments—which once seemed secure, needing only
the continued protection afforded by their status as a national
monument—are increasingly imperiled by the works of man. As the city of
Tucson sprawls in all directions, the monument’s two divisions, islands
in an encroaching sea of civilization, must withstand ever-accelerating
hazards. Vandalism takes an increasing toll of the saguaros; housing
developments creep toward the monument borders. Smog drifts over the
fragile plant communities, threatening to choke them—as the polluted air
from Los Angeles is already strangling forests in the distant San
Bernardino Mountains.
A new awareness that the best-managed preserve cannot thrive
independently of what is happening in the surrounding region only
emphasizes the difficulty of the task. Saving the saguaros is inevitably
tied to the problem of enhancing the quality of life and reversing the
degradation of the environment—not only in Tucson but throughout the
Southwest.
There is no time to waste. Only concerted effort by scientists, resource
managers, and the community can assure that our grandchildren will be
able to visit a Saguaro National Monument where coyotes howl under the
moon, peccaries snort through the washes, and giant cactuses lift
bristly green arms into a blue sky.
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