Last weekend's diary on Canyonlands National Park touched upon an important subject relating to its terrain and typical climate. Thus the subject title of today's diary. For those who are interested in the science behind this fascinating subject, which also entails human history (particularly the Ancestral Puebloans and their successors, the Puebloans), what follows in this diary should also be of interest to DKos community readers. If nothing else, consider this offering another diary I have intended as building a continuing data base of relative subject matter to all the diaries thus far posted and for those still to come.
Prologue: North America's Southwest sector is predominantly a desert and desiccated environment. Characteristically, its landforms are mesa and canyon terrains surrounded by huge gulfs of deserts, with volcanic mountains punctuating the scenery throughout the Colorado Plateauâs expansive territory (130,000 square miles). Yet these predominantly arid environments are not, what some people consider, dead zones. Deserts are alive with life forms of all kinds, alive with myriad ecosystems. This means the ecology thrives, even though harsh environmental rules apply and govern what lives here.
Of course, some desert pavements are as dry as a dinosaur's bone. . .
While other desert landscapes teem with life, but mostly drought resistant life forms that can handle a sparsity of annual precipitation. . .
Of all the desert landscapes in the United States, the famed Painted Desert is considered the most engaging. Just ask one of these guys and find out what s/he thinks about this desert's aesthetics. . .
(Continues after the proverbial fold.)
Locations of deserts have changed throughout time and throughout the world. The change is the result of continental drift (plate tectonics) and the uplifting of mountain ranges, including volcanoes. Modern desert regions are centered in latitudes typically straddling the Tropic of Cancer and the Tropic of Capricorn (between 15 and 30 degrees north and south of the equator). Some deserts, such as the Kalahari in central Africa, are geologically ancient. The Sahara Desert in northern Africa is also ancient, some 66-million years old, while America's Sonoran Desert reached its northern limits only within the last 10,000 years.
Because deserts are poised in such harsh extremes of heat and aridity, deserts are among the most fragile ecosystems on the planet. What follows in this diary are key factors that focus on why deserts are so-named; also, the differences in the Southwest's three primary deserts compared to one another. Again, this background information relates to the Canyonlands National Park, primarily due to the nature of its environmental backdrop, the Great Basin Desert.
What Is A Desert And What Constitutes Desert Ecology? "Desert," as a noun, usually conjures up ideas of a barren, desolate landscape void of life; places with high temperature and no water. However, in the desert Southwest that's simply not the case. Take for example the Great Basin Desert that encompasses featured settings like Canyonlands and Arches national parks. It's the largest desert in the United States and covers an arid expanse of about 190,000 square miles. Bordered by the Sierra Nevada Range on the west, the Rocky Mountains on the east, the Colorado Plateau Province to the north, and the Mojave and Sonoran deserts to the south, its ranging terrain is as diverse as itâs home to a plethora of life forms, both plants and animals. Sometimes its landscape looks like this. . .
And sometimes looks like this. . .
Desert Ecology, as a scientific term, is therefore the sum of the interactions between both biotic (relating to, produced by, or caused by living organisms) and abiotic life forms (the interactions of plants, animals, even bacterial agents that share a desert habitat, its various ecosystems, and form an overall community). Some abiotic factors include latitude and longitude of a specific environment, along with climate and soil. Biotic and abiotic factors thus create adaptations to the essential environment of a region.
Compared to the Mojave and Sonoran deserts, the Great Basin is considered a cold desert due to its more northern latitude and higher elevations. This means its desert ecology is noticeably different from, say, Mexico's Chihuahuan Desert. With an average 7 to 12 inches of accumulated moisture on average annual precipitation, the Great Basin Desert is certainly wetter and cooler compared to a much drier and hotter terrain like the Gobi or Saharan deserts. However, compare the Great Basin's neighboring environment to the Sonoran Desert, which is classified as one of the wettest deserts in North America (averaging from 3 to 16 inches of rain a year, though rarely snowfall). The higher precipitation is because its territory benefits from two usually reliable rainy seasons, one in the summer and another in the winter. By contrast, most of the Great Basin's moisture occurs during the winter, as snow, which is why it's classified as a cold desert environment. Even with this amount of precipitation the potential evapotranspiration exceeds precipitation. When considering crucial factors that constitute a desert, evapotranspiration is important to know and understand (see below for a more detailed explanation).
As previously mentioned, Canyonlands National Park (Moab, Utah) serves as an ideal backdrop for discussing desert ecology, at least this sector of the Southwest where three deserts are common. Canyonlands, the setting, denotes a classic high desert, where geographic landforms typically create a climate characterized by a minimal amount of accumulated annual moisture, also where potential evapotranspiration exceeds precipitation.
Its vast acreage lies at a latitude where dry air masses constantly descend toward the surface of the planet. The area is also in the interior of the North American continent and therefore far away from marine moisture, as well as in the rain shadow effect of the Sierra Nevada Mountains. These underlying main factors act to produce the arid environment of Canyonlands desert ecology. Apart from these typical aspects governed by precipitation and a desert environment, itâs the high elevations throughout the park (4,000 to 6,000 feet) and the winter snow that makes this region what it is: a cold and relatively dry biome. (A biome climatically and geographically is defined as having similar climatic conditions, such as various communities of animals, plants, and soil organisms which are often referred to as ecosystems.) The dryness of the air merely creates a situation where more moisture is evaporated from plants and the ground terrain than accumulates during the year.
Thus the potential for annual evapotranspiration is 8.5 inches. This figure translates to approximately 76 inches more than what's actually available! Low moisture in the air also allows more sunlight to reach the ground, thereby raising daytime temperatures.
There is yet another distinguishing feature of a desert that must be considered: its life forms that thrive in the prevailing climate. In this case, the assemblage of flora and fauna throughout Canyonlands generates a lively blend of plants and animals not found in other deserts of the world.
Geomorphology Of Deserts: Three of the four major deserts of North America are contained within a geological region called the Basin and Range Province, lying between the Rocky Mountains to the east and the Sierra Nevada range to the west. While the distinctiveness of each desert is based on the types of plant and animal life found there, the geological structures of these three deserts are rather similar.
The Great Basin Desert region is a series of many distinct basins which are separated by mountain ranges. The explorer, Captain John Charles Fremont, was the first to coin the term, Great Basin. Each range is roughly parallel and typically has a steep slope on one side and a gentle slope on the other. The basins, or playas as they are popularly called, have no drainage. Playas are also known as dry lakes, alkali or mudflats. If the surface is primarily salt, then these sprawling and sandy stretches are called salt pans, pans, hardpan, salt lakes or salt flats.
One of many Great Basin Desert playa landscapes:
During wet cycles they become shallow playa lakes which may last from a few months, a few years or even longer periods. During the Pleistocene interglacial period (intervals between 40,000 to 100,000 years), much of the Great Basin was flooded producing Lake Lahotan (located in present-day northwestern Nevada which extended into northeastern California and southern Oregon). The lake evaporated during the last 12,000 years, leaving only a few salty lakes between the Sierra Nevada range and the Rocky Mountains. Also known as Quaternary glaciation, this, the most current ice age, refers to the period of the last few million years in which permanent ice sheets were established in parts of the globe. Undrained basins are also characteristic of the Mojave Desert and the Chihuahuan Desert which straddles the Mexico-United States border (western Arizona, southern New Mexico and Texas). It's also the largest North American desert covering some 175,000 square miles. Considering the focus on the Southwest, the Mojave is another classic high desert. Its sprawling terrain covers a significant portion of southeastern California, smaller sectors of central California, southern Nevada, southwestern Utah and northwestern Arizona. The Mojave's landscape and topography displays typical Basin and Range topography. Receiving less than 13 inches (254 mm) of rain a year, the Mojave Desert is generally between 3,000 and 6,000 feet in elevation.
Unlike the Mojave or the Chihuahua deserts, the Sonoran Desert usually has hydraulic systems forming streams draining into the Gulf of California or the Pacific Ocean. There are also a few playas in the Sonoran Desert. One of these, called the Salton Sea, was filled by Colorado River flood waters in 1906 and its basin has remained fairly full. However, over the past twenty or so years water levels have substantially diminished due to a persistent drought throughout much of the Western territory. Its over-tapped resource of water is primarily caused by a heavy encroachment of people living in this part of the West.
Mohave Desert tableau with its common indicator plant in foreground––the Joshua Tree:
And who can forget that classic sci-fi movie filmed in this desert which featured gigantic people-eating ants?
For those who think all desert terrain looks about the same, think again. Here is a typical Sonoran landscape tableau:
Alluvial fans are common in the Mojave Desert and the California portions of the Sonoran Desert. These are formed through geologic time where an arroyo or wash drains a mountain range, depositing the detritus (nonliving particulate organic matter as opposed to dissolved organic material) in a semicircle at the canyon's mouth. In the Sonoran Desert, the linear ranges, which are usually formed by volcanic uplift, are often surrounded by an apron of detritus, boulders, rocks, gravel, sand, soils that have eroded from the mountain over time. Much of this material has been washed down during torrential summer downpours (a/k/a "monsoons"). In the Southwest, these detritus pediments are commonly called bajadas. The substrate is coarser, with larger rocks on the upper bajada and finer at the lower elevation. Deep arroyos may also slice through the bajadas. Unique plants such as the desert ironwood (Olneya tesota) and canyon bursage (Ambrosia ambrosioides) may grow along the arroyos, giving them the appearance of dry creeks.
Example of an alluvial fan:
Over the eons areas between the desert ranges have been filled with sedimentary material, namely water-washed alluvium. Alluvium, which is a fine soil, produces the extensive flat spaces one usually associates with deserts. This byproduct is relatively young material and is generally referred to as cover because these sediments obscure the underlying bedrock. In these places where alluvium is common, the water table may be high on the flatlands and the drainage is often slow. Poorly drained patches and larger playas become alkaline through accumulation of soluble chemicals. Special types of plants called halophytes (otherwise known as "salt lovers") can grow here. However, not just plants prefer alluvium which can anchor in its cover, but prospectors sought these places because alluvium sometimes contains valuable ores (gold and platinum) and a wide variety of gemstones. These concentrations are termed a placer deposit.
Riparian Eden Zones: Desert streams and rivers are always a wonder to see and find. They form where there are grasslands, semiarid woodlands and forested uplands called watersheds. Like effective geological sponges, the upland watersheds collect and hold water throughout the year, while releasing it slowly into the desert below. These desert streams with their riparian woodlands of cottonwoods (Populus freemontii), willows (from the genus Salix) and other hydrophilic (meaning "water loving") plants are often centers for abundant wildlife, as well as native people. However, abuse to the watersheds through cattle and sheep overgrazing, timber cutting, mining and other manmade activities has dried up many of these resources. Regrettably, much of the water table, once just below the desert pavement, has been pumped lower and lower mainly due to agriculture and the fruit industry. In most places, the water table is now hundreds of feet below the surface and getting lower as the years pass and still the prolonged drought continues.
A Sonoran riparian scene like this. . .
Often means one or more of these guys show up. . .
Of course, everything eats everything else in one way or the other, and riparian locales tend to be, well, akin to local restaurants and such. . .
But once in a while the prey can turn predator. In this case, can he eat what's on the plate (or floor)? I'm betting he can!
The Sonoran Desert: Perhaps the most endangered desert of North America is the Sonoran. Due to over population and water-craving interests its fragile terrain is constantly in harm's way, mainly due to over development and industries of all kinds. The Sonoran's expansive and arid region covers 120,000 square miles in southwestern Arizona and southeastern California, most of Baja California and the western half of the state of Sonora, Mexico. Subdivisions of this hot and typically dry region include the Colorado and Yuma deserts. Modern day irrigation has produced numerous fertile agricultural areas, including the Coachella and Imperial Valleys of California. Warm winters attract tourists to Sonora Desert resorts in Palm Springs, California, as well as Tucson and Phoenix, Arizona. Despite the excessive load placed on its turf, the stress on this desert environment continues and there is no end in sight. The unique feature of the Sonoran Desert is the fact it's the hottest of the North American deserts. Yet there's a distinctly bimodal rainfall pattern that produces a high biological diversity. Winter storms from the Pacific nourish many West Coast annuals such as poppies and lupines, while well-developed summer monsoons host both annuals and woody plants originating from the south. Freezing conditions can be expected for a few nights in winter.
Trees And Plants Of The Sonoran: Unlike other deserts, such as the aforementioned Gobi or Sahara, a variety of trees are usually well developed on the Sonoran's desert ranges and bajadas. Often abundant on these well-drained soils are little-leaf palo verde trees (both yellow and blue varieties), desert Ironwoods (Olneya tesota), catclaw acacias (Acacia gregii), mesquites (Prosopis pubescens), and the giant and iconic saguaros (Carnegiea gigantea). The understory consists of three, four or even five layers of smaller woody shrubs. Tall chollas (Genus Opuntia) are also common and may occur in an almost bewildering array of species. On the alluvial lowlands, these sectors host communities of desert saltbush (Atriplex polycarpa), wolfberry (Lycium chinense) and bursage. Where coarser soils are found, creosote bush and bursage (Genus Ambrosai) communities may stretch for miles. If the water table is high, then honey or velvet mesquite may form dense bosques (Spanish for "woodlands"). Other trees are restricted to alkaline areas. Stream sides may be lined with riparian woodlands composed of Arizona ash (Fraxinus velutina), Arizona black walnut (Juglans nigra), Fremont cottonwood and various willows, with a dense understory of arrow-weed (Pluchea sericea), seep-willow (Baccharis salicifolia) and carrizo (Ammophila arenaria). The Sonoran Desert is indeed abundantly rich in animal life as well, with many species in all groups derived from tropical and subtropical regions.
The western part of the Sonora Desert (sometimes called the "Colorado Desert") is closer to the source of Pacific storms and is noted for spectacular spring flowering of ephemerals when there's ample winter-spring rainfall. However, the western portion is relatively depauperate (arrested in growth or development), and lacking many of the species such as the saguaro that depend on good summer rainfall.
Trust me, in this Colorado Desert or any other desert you do not want to accidentally run into this stuff––chollo. (Of course, it also goes by a lot of other expletive-deletives):
Facts Of Ecosystems Dependent On Available Moisture: Returning to the example of Canyonlands, typically its terrain denotes a hot, arid landscape during the warmer months of the years, while the Sonoran and Mojave deserts are areas of more extreme heat and dryness for most of the year. From a scientific perspective, deserts in the lower latitudes of North America characteristically receive less than 10 inches of precipitation a year, but more recently the figure is about 8 inches. In many deserts, the amount of evaporation is also greater than the amount of rainfall. Semiarid regions average 10 to 20 inches of annual precipitation. Generally, desert moisture occurs in brief intervals and is unpredictable from year to year. About one-third of the planetâs land mass is arid to semiarid (either desert or semidesert).
Effects Of Evaporation: Evapotranspiration and evaporation are therefore key terms that best describe the opening question, What is a desert? Evapotranspiration describes the sum of evaporation and plant transpiration from the Earth's land surface to the atmosphere. By itself, evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies. Transpiration, however, is what accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata (a microscopic pore) in its leaves. Yet it's the evapotranspiration characteristic that is the pivotal aspect of the water cycle. Both are important factors contributing to aridity.
Although deserts have other means to add to the amount of precipitation (plants and dew), from the above explanation and diagram we see how the amount of water evaporation still exceeds the amount of precipitation. There is also the importance of how temperature affects these arid regions. For instance, rising air cools and can hold less moisture, thereby producing clouds and precipitation. By contrast, falling air warms and absorbs moisture. Regions like Canyonlands having few clouds, bodies of water and little vegetation also absorb most of the sun's radiation, thereby heating the air, but at the soil surface. Compare this to more humid areas that deflect heat in clouds, water and vegetation and remain cooler. High wind in open country also contributes to evaporation.
Flora: Desert plants, since they are rooted in place, must be able to deal with variations in temperature and amounts of available water. Intense sunlight can also be extreme and harmful to these varying life forms. Again using Canyonlands as an ideal model and example, temperatures here fluctuate greatly, both daily and annually. In summer, highs climb well over 100 degrees (all readings given in Fahrenheit), while winter temperatures often drop below zero. On a hot summer day the temperature may fall 30 - 50 degrees as night approaches. Chiefly, itâs the low humidity and lack of cloud cover that governs this usual pattern. As the sun sets, rock and sand, which are both poor capacitors for retaining heat, release almost ninety percent of their captured solar energy back to the atmosphere. Without clouds to contain the heat the air temperature rapidly cools. Surface temperatures in direct sunlight are commonly 25 - 50 degrees warmer than the air temperature some 6 feet above the ground. Temperatures in the shade may also be cooler by twenty degrees or more. Compare the Great Basin's temperature to the Sonoran Desert. The Sonoranâs seasonal temperatures range from an average of 52 degrees in the winter, to 86 degrees in the summer. In some seasons the temperature can reach 32 degrees at night! In some portions of the desert, for instance near the tip of Mexico, the temperature can reach a high of 134 degrees in the shade!
Speaking of heat, at the bottom of the Grand Canyon, where I have spent many, many years hiking and teaching, the inner canyon temperatures reflect the Lower Sonoran Desert temperatures (because at the bottom of the canyon the climate is the same, and the same goes for typical plants and animals. This temperature reading taken at the Bright Angel Campground (about a twenty minute walk from Phantom Ranch) indicates a mid-morning temperature (from around April thru September). By mid-afternoon the gauge will easily read 120 degrees. For you folks from Missouri, no kidding!
And here's a hiker to prove the point. (He's also standing and grinning near Indian Garden, which is about 4,500 feet above sea level (Phantom Ranch is 2,400 feet). Of course, the deeper into the canyon you go, the warmer it gets.
P. S. This man is not one of my backpacking students. How do I know this? Because he or she would be more stoic looking! (You know, having to listen to all my chatter, jokes and trail humor!)
The Ingenuity Of Plants: Winter snow and violent thunderstorms also fall on thin, sandy soils that can't retain too much moisture. So, how do desert plants survive these extremes? Some plants, referred to as drought escapers, make use of ideal growing conditions found in the spring when temperatures are cooler and moisture is more abundant. These annual plants also have a short life cycle. They germinate, sprout, grow, bloom, seed and die in a matter of days or weeks. Their rotation is predetermined, in that the life cycle is completed before the hot, dry days of summer arrive. An example of escapers are the spring wildflowers that occur in showy abundance early each new year.
Perennials, which are plants that live longer than one year, must also contend with desert extremes in other ways. The so-called drought resistors among them are hardy plants that have made adaptations to endure harsh extremes. For example, cacti store water within their spiny forms, blackbrush drop their tiny, leathery leaves in dry weather, and yucca plants have extended tap roots. These slender tentacles can reach depths up to 30 feet, and therefore find deeper water sources underground. Many desert plants also have lightly colored, highly reflective leaves that add to the plant's defense mechanisms. Such mechanisms is really what's behind all the greenery and life forms.
This is a typical garden-like scene where water in the desert is ample:
This scene, however, is where humans have messed about with the water table and seemingly brought Eden to the desert. Ultimately, such landscaping will fail because the water table is over tapped and getting deeper below the ground. Not good!
Another adaptive technique is found in life forms that are classified as drought evaders. These softer plants have even more radical adaptations. Moss, for instance, is a plant not commonly associated with deserts. Moss thrives because it can live through long periods of extreme drying. When water is unavailable, it literally dries up. Conversely, when water is plentiful, it soaks up moisture. The green tincture happens almost immediately. Mosses are usually found growing in the shade of larger plants or in cryptobiotic crust (see below). Meanwhile, do you know what this life form is having for its meal?
You guessed it: a big rock. Isn't it neat how Nature continues to both feed and dissolve its workers? I'm thinking.
Another extreme adaptation can be found in the Utah juniper tree (Juniperus osteosperma), one of the most common trees in the Southwest. The juniper tree, also commonly (and erroneously) called a cedar, requires copious amounts of water. During drought conditions, however, it shuts off water flow to one or more branches. Although this strategy kills only particular branches directed affected by a lack of water, the juniper tree preserves enough water to allow other parts to survive. There are also other desert plants that may likewise grow only in specialized habitats. For instance, moisture dependent monkey and Easter flowers and ferns thrive in well-shaded alcoves with dripping springs, while cottonwood, willows and cattail, which require copious amounts of water, thrive on river banks.
A tree with numerous purposes, the Utah Juniper:
Nature's Most Fragile And Useful Desert Pavement Life Form: A unique desert plant community throughout much of the Great Basin Desert canyon country is the aforementioned cryptobiotic crust (a/k/a âbiocrustâ). This crumbly and crusted black soil is made up of fungi, lichen, algae, moss and bacteria. These life forms all live together in a symbiotic relationship, meaning all the members benefit from their communal coexistence. Cryptobiotic crusts are very important to the desert community for many reasons: it stabilize the soil, prevent erosion, retain water, and provide important nutrients such as nitrogen to plants. Additionally, a plant seed that lands in cryptobiotic crust has a greater chance of survival than a seed that lands in loose, dry sand. Unfortunately, cryptobiotic crusts are extremely fragile. One misplaced footstep can quickly turn crust to dust, then recovery and regrowth may take decades.
I know, this stuff doesn't look like much, but it truly is extraordinary and very fragile. Hence, do not walk on such a black pavement for reasons just mentioned.
Note: Biological soil crusts are also known by other names. For instance, cryptogamic, microbiotic, microphytic and cryptobiotic. These designates are all meant to indicate common features of the organisms that compose the crusts. The most inclusive term is probably biological soil crust which distinguishes this soil stabilizer from mere physical crusts, while not limiting crust components to plants. Whatever name is used there remains an important distinction between these formations and physical or chemical crusts. The key factor to know about crusts is that they are primarily composed of cyanobacteria which formerly is known as blue-green algae, green and brown algae, lichens and mosses. Other important components can be fungi, liverworts (a division of bryophyte plants commonly referred to as hepatics) and a variety of bacteria.
Got blue-green algae? It's what's good for you!
The Significance Of Lichens: Exposed rock surfaces are often covered in part by lichens, especially the shaded north side. A lichen is essentially a simple community of at least two mutually dependent organisms: fungi and green algae. When both organisms are dependent on the other, they are said to be symbiotic. Green algae requires a photosynthesis process to produce food for the fungus, while the fungus protects the algae from the elements and extracts nutrients from soil and rock. The lichen structure is more elaborate and durable than either fungus or algae alone. Lichens are well adapted to arid climates and therefore thrive throughout the deserts of the Southwest. They can continue food production at any temperature above freezing. They also absorb more than their own weight of water, even ephemeral water (dew) that almost passes directly into their cells. Ergo, the moisture doesnât need to pass through roots and stems as it does in vascular plants.
I'm thinking these lichen are liking this rocky surface. What do you think?
Many other plants benefit from the presence of lichens as well. One example is how the green algae component of lichens transforms nitrogen in the air, which is unusable to most organisms, then into a process and means which is essential for life. This is especially important in arid climates where lack of nitrogen is known to limit productivity. Because lichens take everything they need from the air, they are dependent on good air quality. Scientists therefore favor lichens as reliable indicators of air quality, much like the proverbial canneries in coal mine scenarios that once gave warning to miners if the air was bad or lethal.
Plant Dependency: Symbiosis in the plant community is indeed a gift of nature. Consider how the yucca plant and the yucca moth have a fascinating dependency on one another which includes trysts in the night. After mating, the female moth gathers pollen from a yucca flower and packs it into a ball. She then flies into the night until locating another yucca flower. Yucca flowers are only pollinated by yucca moths and yucca moth larvae only feed on yucca pollen. These kind of established symbiotic relationships for the benefit of the whole ecosystem works brilliantly, from the smallest life forms to the largest.
The Seasonal And Transient Beauty Of Wildflowers: Wildflowers have adapted to the desert arid climate in many unique and different ways. Thick, waxy coverings on leaves and stems reduce evaporation, while small leaves reduce the effects of solar radiation and water loss. Deep taproots also reach far into the soil to find water sources, while shallow, widespread roots catch and absorb surface water. Despite these adaptations, wildflowers avoid drought and heat by literally hiding in the soil as seeds or bulbs, sometimes for decades. Germination only occurs after significant seasonal rainfall.
While most wildflowers bloom during the day, some take advantage of cooler night temperatures to open their flowers. Late afternoon or evening-blooming plants include sacred datura (Datura wrightii), sometimes called jimsonweed in the West, sand verbena (Abronia ammophila), evening primrose (from the species Oenothera) and yucca (from the family Asparagaceae). April and May, following winter snow and rain, are generally the best months to see wildflowers throughout the Southwest. Beginning in late August, and if the summer monsoon season has brought significant rainfall, various species bloom and color the landscape. Not only is the blooming and color show appealing to the eye, but the pollinators also favor the seasonal show.
Fauna: A few drops of water, a patch of shade or an underground retreat are seeming small things afforded by nature, yet these chance opportunities and hiding places just might provide the lifesaving edge for desert animals. Like plants, most of these critters have special and unique adaptations to cope with temperature and moisture stresses. Since animals are mobile, they can also deal with their environment through behavioral adaptations. Some even have physiological changes as well.
For instance, adapting to a microclimate is one way desert animals adjust to their environment. Lizards and snakes retreat to shady areas or underground burrows during the heat of the day. They may even mimic the spade foot toad and become dormant during unfavorable seasons. A jackrabbit is another prime example. It will rest during the day and seek food at night. Jackrabbits also roost in a slight hollow in the shade with their big ears lying flat along their back. The ears are not just for show, but display a high reflectivity to light. When the jackrabbit gets too hot, blood vessels in its long ears dilate, causing heat in its body to radiate back into the air. This species in the family Leporidae is also a good example of both behavioral and physiological adaptations.
And, yes, this dude is as big as he appears; like a medium-sized dog (or larger):
Considering a much smaller species, the kangaroo rat (genus Dipodomys) lives its entire life eating only dry plant food and never drinks water, because its body produces water by metabolizing the dry food it eats. Active only at night, this clever creature spends the day sleeping in its cool burrow underground, but first plugging the opening with dirt which keeps the heat out and the moisture in. The other unique feature about this species is that it doesn't need to urinate. Instead, it deposits uric crystals, thus preserving its energy even more.
Waste not, want not and that way I get to keep all the moisture for myself. I never even wet the bed!
Water, of course, is the elixir of the desert, especially when it's hot. Some large animals are more dependent on this invaluable resource, solely relying on their mobility to reach water sources. Bighorn sheep (Ovis canadensis), especially the Desert Bighorn genus (Ovis canadensis nelsoni) and mule deer (Odocoileus heminus), for example, must have access to water. Their powerful bodies provide the energy to transport them many miles to the river, a rain-filled pothole or perhaps a spring. In addition, a considerable amount of water is derived from the plant food they eat. It follows how bighorn and species of deer are able to go several days in between drinks. Carnivores, like the coyote (Canis latrans), bobcat (Lynx rufus), cougar (Puma concolor), commonly called mountain lion or cougar, and birds of prey all rely heavily on the fluids found within the animals they eat to supplement the water they drink. Fur and feathers can also play a dual role in some animals by shielding them from the sun during the day and insulating them from the cold at night. Animals with a short and sleek pelage are still able to lose heat fairly easily after exertion simply by laying the hair down flat against their bodies. Birds can droop their wings down and away from their bodies allowing heat to escape from their thinly feathered undersides. Birds and large mammals also commonly pant as a means to increase heat loss.
Come out, come out wherever you are. . .I'm hungry!
Conclusion: From the general information explained in this diary it's noted how deserts really are not dead, sterile zones devoid of life. They are, instead, thriving regions that demand adaptation by plants and animals that depend on such environs and whatever the general climate. The interdependent ecosystems, many of which are symbiotic, produce a plethora of life forms. . .plants, animals, trees, including the smaller, though still important, contributors, such as lichens and cryptobiotic soil. But like any desert, common sense is called for when exploring these ranging realms. Mainly, knowing where water is and how to protect one's self from the elements. Knowing how desert ecology works is also like understanding the mind of the desert. This is how all life forms function in these more demanding environments.
Since this diary entails what lives where and who eats whom I thought I'd leave you with this handy illustration, which shows all the main players in the scheme of things:
In other words, this explanation says it all:
As always, the community's thoughtful commentary is greatly appreciated.
Rich
http://www.nmstarg.com/...
A parting shot of canis latrans. . .the "trickster" of folklore and a true wonder to hear and behold in his or her domain!
