There is no one definition of a desert that is accepted by all. The boundaries of the Chihuahuan Desert, like those of most other deserts, change radically depending on the definition accepted. Some definitions are based on various climatic factors, while others combine climatic and biotic features, and some rely solely on vegetation and/or animal life. Morafka (1977a:3-4) points out that, "The desert has been analyzed and defined ecologically, at least in English literature, largely from its unstable and atypical grassland ecotones lying within the United States boundaries." He goes on to note that this would be similar to analyzing the contents of an egg by extrapolating from a shell sample. Things have improved in the over 20 years since this assessment, but the Chihuahuan Desert still remains North America's poorest known desert.
As a basis for discussion for this web site, the boundaries of the Chihuahuan Desert as defined by Schmidt (1979) have been adopted, while keeping in mind that there are other defensable geographic limits.
Schmidt's definition is based on de Martonne's Index of Aridity as set forth in the English language version (de Martonne, 1927), and Schmidt's discussion is used as the basis for the following comments. The Index of Aridity is obtained from the formula Ia = Pmm/T°C+10, where "Pmm" is annual precipitation in millimeters and T°C is average annual temperature in degrees Celsius. The lower the index, the more arid the climate. de Martonne considered true deserts to correspond to an index of less than 5, with dry steppes from about 5 to about 10. Schmidt considered as desert those areas having an index equal to or less than 10. His boundaries are based on data from almost 800 weather stations in the southwestern U.S. and northern Mexico, with about 115 of these being within the finally determined bounds of the desert.
Greater Chihuahuan Desert Region (which includes not only the desert itself, but also the highlands surrounded by the desert and those peripheral to the desert).
he Chihuahuan Desert Gardens are designed to show that such landscaping can go far beyond the gravel and cactus yard that so many people have been led to believe is the only choice.
kinds and numbers of invertebrates in the Chihuahuan Desert far exceed those of the vertebrate
bol·son n. Chiefly Southwestern U.S. A flat arid valley surrounded by mountains and draining into a shallow central lake.
Hemmed in on all sides by highlands, drainage generally is internal, with playas (so-called "dry lakes" which usually hold water only seasonally) located in the lowest portions of the basins. Exceptions to this drainage pattern are where rivers originating in highland areas, usually outside of the desert region,
The Rio Grande is an excellent example of this, originating in the high mountains of Colorado and New Mexico and flowing south and southeast through formerly separate, close-drainage basins.
Franklin Mountains, El Paso County, Texas ... protected from development by virtue of a past in which it was an Army firing range; unexploded ordnance renders the area dangerous and too costly thus far to clear.
Despite the barren appearance, canyons and other protected areas harbor a great diversity of animals and plants.
In general, increasing elevation results in cooler temperatures and greater effective moisture, and topographic relief provides a number of habitats unavailable in the flatlands. South-facing and west-facing slopes tend to be relatively hot and dry compared to those facing east or north, for example.
higher mountain ranges within or bounding the desert often support woodland and forest, and are separated from other such plant communities by surrounding grassland or desert. The Animas Mountains of extreme southwestern New Mexico are a good example of what popularly are called Sky Islands.
Igneous outcrops may form massive ranges, such as the Organ Mountains, medium-sized peaks, or flat lava flows--and every permutation between.
suitable ford across the Rio allowed passage across the river, an important point on the Spanish-era Camino Real (the "Royal Road", running from Mexico City to Santa Fe, New Mexico).
Air pollution is a fact of life for the larger cities in the valleys and bolsons of the desert, particularly during winter
Much of the agricultural wealth of New Mexico and the El Paso Region is entirely dependent on the flow of the Rio Grande, and much of the municipal water of El Paso comes from the river.
the current river valley is far different than when first encountered by the Spanish in the late 16th century.
introduction of exotic plants has greatly changed the riparian vegetation
Franklin Mountains State Park, apparently making this the largest urban park in the country.
many drainages in sky islands, Indian Creek flows only intermittently
To survive in an arid region, organisms must either find habitats where aridity is not a problem or must have adaptations that allow them to withstand low levels of moisture
[deserts] often including a lack of permanent lakes and waterways that are ephemeral except close to their source
Other common characters are reductions in relative humidity and cloud cover, both of which tend to further increase evaporation and contribute to large temperature fluctuations.
The Chihuahuan Desert is relatively well watered (relatively mesic), but some 60 to 80% of the precipitation falls during the summer months when evaporative losses are greatest, with only about 3 to 20% falling as winter precipitation Morafka (1977a)
average annual relative humidity of less than 50% and with cloudy days averaging less than 60 per year.
Why the aridity? Several factors contribute. For one, the Chihuahuan Desert lies at the latitudes where air converging from the south and north sinks. As the air sinks, it becomes compressed, which heats it and thus decreases its relative humidity.
Sierra Madre Occidental and the Sierra Madre Oriental. Moisture-bearing winds originating over oceanic waters are forced by these high mountain ranges to rise. As air rises, it expands and cools. The cooling forces the air to drop much of its load of moisture on the windward slopes of the highlands. An additional factor here is that condensation of moisture releases heat, with the result that as the air sinks and becomes compressed on the desert side of the mountains, it is not only drier, but also hotter than it started out.
Absolute humidity is the amount of moisture in a given parcel of air. Relative humidity is the amount of moisture relative to the amount that could be stored in that parcel of air given the temperature of the air. The warmer the air, the more moisture it can hold, and vice versa. Thus an absolute humidity that results in 100% relative humidity at a low temperature may result in a relative humidity of, say, 15% at 102°F.
evaporative water loss is strongly influenced by the relative humidity
Water loss by plants, animals, soil, etc., may be negligible in high humidity; at low humidity, it may be life threatening. Since temperate- and tropical-zone deserts typically have low humidity (especially during the hot season), adaptations to prevent water loss are critical for most desert organisms.
Orographic Precipitation , mountains, rain shadow on the leeward side. Smaller ranges also can have rain shadows, though of lesser extent.
Clouds tend to reflect heat radiated from the surface of the earth, as well as reflecting a portion of incoming insolation
scarcity of clouds in a desert area is rapid heating during the day and rapid cooling during the night, resulting in the classic large differential between daytime and nighttime temperatures.
lack of a good plant cover that tends to restrict ground heating, rocks and soil in the desert heat up rapidly and transfer much of the heat to the air immediately adjacent to the surface ... warm air rises ... rising air condenses into puffy cumulus clouds ... thunderstorms that provide most of the Chihuahuan Desert summer rains.
relatively high desert, with base level (basin floors) running mostly from 900 to 1200 m (ca. 3000 ft to 4000 ft), and it's big. It spans more than 11° from north to south and covers some 357,000 km2 (137,840 mi2). In general the lower elevations tend to be on the eastern side, with the desert floor sloping upwards to the central and western portions
numerous mountain ranges bound the desert basins. These are mostly northwest trending mountains that generally rise some 600 to 1200 m (ca. 2000 to 4000 ft) above the basin floors. Schmidt considered 1800 m (ca. 6000 ft) as the upper limit of Chihuahuan Desert climatic conditions, and thus the higher of these ranges support non-desert climatic regimes. Such ranges, supporting non-desert plants and animals, often are known as sky islands, and they usually are considered as part of the Greater Chihuahuan Desert Region
Pleistocene ice ages (ending roughly 10 thousand years ago) when temperatures were cooler and effective moisture greater.
[internally draining basins lead to deposits]
Dissolved material precipitated as water evaporated has left many of these old lake beds and playas with heavy deposits of salts and other minerals. The pure white sands of White Sands National Monument consist mostly of gypsum dissolved from the San Andres Mountains to the west and precipitated out in lake waters between the mountains and the current sand deposits [pic whitesands pedestal.gif]
In general, the northern parts of the desert are subjected to occasional hard freezes; this restricts frost-sensitive plants to low elevations in the north (portions of Big Bend)
microhabitats favor or disfavor specific kinds of plants and animals. A microhabitat is a set of climatic, biological, or physical (or combinations of these) of limited extent that differs importantly from other sets of conditions. Some microhabitats are obvious, such as a desert pool; others may be subtle, such as a difference in the chemical composition of a soil.
That desert pool supplies meaningful resources to fish, insects that live in water at some stage (such as dragonfly or mosquito larvae), birds and mammals that require drinking water, plants that require constant moisture in the root zone and thus may live adjacent to the pool, etc. On the other hand, the pool microhabitat is unsuitable for cacti and superfluous for most insects.
Availability of water and situations that tend to conserve moisture obviously are important in a desert habitat.
perhaps up to thousands of geothermal springs, lakes, and streams in the Cuatrociénegas Valley.
All else being equal, a south-facing slope is hotter (and thus usually drier) than level ground or north-facing slopes. As a result, of course, north-facing slopes tend to be cooler and preserve moisture longer. These factors often tend to build up to greater differences. Because of the cooler temperatures and more available moisture, northern slopes often have more vegetation; this, in turn, may slow down rain runoff, allowing more moisture to sink into the soil. Although of more importance at high elevations and farther north, areas where there is significant snow tend to have colder temperatures in winter time on south slopes; snow tends to linger on the north slopes, acting as insulation from nighttime lows.
near Socorro, New Mexico. For a fair stretch, the south slopes and level areas between arroyos are in creosotebush, but the north slopes support grasses
an igneous range and a limestone range receiving the same precipitation may have very different floras. The reason is that limestone dissolves relatively rapidly as acids formed by plants (carbonic acid resulting from interaction of carbon dioxide produced by plant-root respiration and ground water) eat away the limestone, resulting in fissures; also, the layered, brittle limestone tends to fracture along joints that then may be enlarged by solution. The result is that precipitation tends to drain quickly beyond the root zone and thus is effectively lost.
Lava beds and boulder fields ... young lava beds often have deep crevices, and boulder fields may have passageways open deep into them. This not only provides shade from the summer sun, but if deep enough, may collect cold air in the depths during winter and, the cold air being heavy, it may linger through the warmer season. Animals may take advantage. For example, the Mexican packrat (Neotoma mexicana) occurs at notably lower elevations than its normal elevational range in the Carrizozo lava beds and in boulder fields near Truth or Consequences, New Mexico.
Many organisms essentially construct their own microhabitats. Most burrowing animals have a very different habitat than if they were not burrowers. Many insects (e.g., ants, termites) burrow extensively as do many vertebrates. Various mice, for example, spend daytime in a burrow and may block the tunnel with soil. The result is relative coolness (soil is a good insulator) and high humidity (both from any moisture that might be in the soil and from moisture produced by the rodent by respiration).
Although not widely used except in the Southwest, Merriam's Life Zones are useful to quickly characterize the different biotas seen at different elevations. Although the desert proper falls entirely within the Lower Sonoran Life Zone, mountain islands within the desert or bounding it often support one or more higher-elevation zones. Following is a brief (overly brief) rundown.
Lower Sonoran Life Zone - Encompasses what we normally consider desert and also desert grassland. El Paso is in the Lower Sonoran Life Zone. Typical plants include Black Grama (Bouteloua eriopoda), Lechuguilla (Agave lechuguilla), Creosotebush (Larrea tridentata), Tarbush (Flourensia cernua), and Ocotillo (Fouquieria splendens). Some typical mammals include Merriam's Kangaroo Rat (Dipodomys merriami) and Mearns Grasshopper Mouse (Onychomys arenicola).
Upper Sonoran Life Zone - Encompasses cooler grasslands (such as those in northern New Mexico) and woodland. Woodlands are usually open (that is, of widely spaced trees) forests of short trees or tree-like shrubs, usually less than 30 feet tall. The most common woodland in our area is pinyon-juniper woodland. However, pinyon-juniper-oak and oak-pine woodlands also occur within the boundaries of the Chihuahuan Desert Region. Generally, woodlands occur on shallower and topographically more diverse soils than the Upper Sonoran grasslands, though overgrazing and other mistreatments of the grasslands may result in invasion by woodlands. Some typical plants include Blue Grama grass (Bouteloua gracilis) and several species of piñon (Pinus) and juniper (Juniperus), the species involved varying with the geographic area. Some common mammals include the Pronghorn (Antilocapra americana), sometimes wrongly called antelope, the Cliff Chipmunk (Tamias dorsalis), and Black-tailed Prairie Dog (Cynomys ludovicianus).
Transition Life Zone - In the northern Chihuahuan Desert, generally Ponderosa Pine forest, though other pines occur at similar elevations farther south. The zone often includes Gambel Oak, particularly where burned or logged off, and Douglas Fir is an ingredient in the higher portions.
Canadian Life Zone - Spruce-fir forest, similar in overall appearance to the trans-Canadian spruce-fir forest, or taiga. Aspen replaces Gambel Oak as the main disturbance tree. This forest essentially is a boreal (northern) forest extending far south along the higher elevations of the Rockies and, south of the Rocky Mountains, into the northern desert region at high elevations of the Basin and Range mountains, such as Sierra Blanca and the Sacramento Mountains.
Hudsonian Life Zone - This and the following life zone occurs almost entirely north of our region at high elevations. As one nears the climatic timberline (either at high elevations or in the Far North), the coniferous forest trees become stunted (and a few different taxa appear). Sierra Blanca is considered by some to have a small representation of this zone.
Arctic-Alpine Life Zone - In the Southwest, this is the area above timberline (in the arctic, the area north of timberline), inhabited by grasses, sedges, and various herbs. We do not have representatives of this zone nearby (the nearest are in northern New Mexico). We frequently, as on Sierra Blanca, see extensive meadows without trees (balds), but these are not above true timberline (such balds usually are on westerly slopes - on north and northeastern slope, trees continue to the top of the mountains, indicating that cold temperatures are not limiting tree growth, as would be the case with true arctic-alpine conditions).
Some desert plants have a double system [tap and fibrous roots], one set of roots near the surface and another that delves deeper; creosote bush is an example.
oo much dissolved material (such as salts) in the soil, a plant can die from lack of water even when in moist soil. The beds of playa lakes often present this situation, leaving them entirely [almost, a few are there] free of plant life
Plant leaves tend to be potential areas of water loss. When surfaces are unprotected or underprotected, molecules of water diffuse out into the surrounding air. Although at a cost, this is solved by many desert plants by applying a layer of waterproofing to the outside of the leaf. This substance, usually waxy in nature, does a reasonable job if fairly thick, but is metabolically expensive to manufacture. Decreasing the size of leaves both decreases the surface area through which water loss can occur and requires less waterproofing material; of course, it also decreases the leaf area for photosynthesis, one reason that many desert plants are slow growers.
in order to carry out photosynthesis, the plant needs to get carbon dioxide into the leaf, and the source is the air outside of the leaf. Small openings in the leaf (each one a stoma; plural, stomata) allow outside gases into the interior of the leaf. A stoma, however, is a two-way door: water inside of the leaf is free to diffuse to the outside, a process known as transpiration. The stomata, like doors, can be opened and closed; but closing the stomata to conserve water means that the carbon dioxide necessary for photosynthesis cannot get in. Thus some plants can access carbon dioxide only during the cooler parts of the day, when transpiration is much slower than at hotter temperatures. When the stomata close, making carbon dioxide unavailable, photosynthesis ceases, yet another reason for slow growth.
Many desert plants have solved the problem to a degree. A number of them use physiological pathways that quickly capture carbon dioxide, allowing the stomata to be closed more often than in plants not adapted for this. These so-called C4 plants (as opposed to C3 plants without the adaptation) also do much better in strong light and hot temperatures. C3 plants under such conditions tend to burn more carbohydrates than they manufacture. Many warm-climate grasses and such things as four-wing saltbush are C4 plants. Cacti and many succulents (such as the century plants, or agaves) utilize a different physiological strategy call CAM photosynthesis. The stomata generally are opened at night, when temperatures tend to be cooler and relative humidity higher, and the carbon dioxide stored in the form of an acid; during the day, the stomata are closed and photosynthesis uses the stored carbon dioxide. CAM plants also can go into a slowed mode for extended periods of time during particularly hot, dry periods by closing the stomata and utilizing carbon dioxide from cellular respiration to manufacture food and burning food to supply energy for respiration. This makes some sense if you know that plants, like animals, produce carbon dioxide as a waste product when breaking down food stuffs to produce usable energy. Of course, energy is lost at each such cycle and eventually the process runs down.
Other strategies for water conservation include dropping the leaves during dry periods, thus greatly decreasing transpiration. Ocotillo is noted for this.
A different strategy for surviving in a water-challenged habitat is undertake the life cycle only during times when enough water is available. Annuals are plants that complete their life cycle within 1 year (and usually far less than that). A number of desert annuals germinate during the spring, taking advantage of winter precipitation and finish flowering and setting seed before the hottest, driest time of the summer. [like] Mexican poppies
few or none germinate if the winter precipitation fails; the seeds lie dormant until conditions are suitable. Several years may pass between conditions suitable for germination, and for many such species, only a portion of the seeds germinate during the good times - a hedge against times when things start out well and then turn ugly.
A somewhat different twist is waiting until precipitation sufficient to support the plant through maturity and reproduction falls.
Euphorbiaceae: Spurge Family. The spurges, or euphorbs as they often are called, belong to a widespread family concentrated in the tropics of the Old World and South America, but also into warm temperate regions, such as southern USA. There are some 245 genera and 6,000 species. Some familiar members include the Castor Bean, Manioc, and Poinsettia. Some of the plants sold in nurseries as cacti actually are euphorbs, some of which fill part of the cactus niche in Africa, particularly (the Cactaceae is a New World family). There is a wide variety of life forms, from small forbs to trees. Characteristically, the sap is milky and, in some subdivisions of the family, poisonous.
Among a number of euphorbs in the Chihuahuan Desert, Candelilla is well known to many of the public.
Rhamnaceae: Buckthorn Family. Another widespread family, especially in the tropics and subtropics. Most members are trees or shrubs, some are vines. Many bear thorns. In the Chihuahuan Desert, various shrubs belong to the family, including Graythorn, Texan Hogplum, Javelina Bush, and Warnock's Javelina Bush.
Fagaceae: Beech Family. Although commonly known as the beech family, the oak family would be a better common name. The Chihuahuan Desert has a large number of oak species, although above the true desert for the most part. One of the elevationally lower is Scrub Oak. Another is Arizona White Oak. The large number of oak species produce acorns important as wildlife food.
Anacardiaceae: Sumac Family. Also known as the cashew family, the cashew being one of the well known members. Others include the Mango and Pistachio and, of course, everyone's favorite: Poison Ivy. Several widespread shrubs of this family occur in the Chihuahuan Desert, including Rhus microphylla and Rhus trilobata. The former is widespread in desert habitats; the latter more common in foothills and canyons and at higher elevations. Several other shrubs of the genus Rhus occur in the region as does, usually at higher elevations, Poison Ivy.
Rosaceae: Rose Family. The rose family is well represented in the Chihuahuan Desert Region with several prominent members, including Apache Plume, Southwestern Chokecherry, California Rosewood, and Mountain Mahogany.
Cactaceae: Cactus Family. The prickly pear cacti, consisting of a number of species, have their stems flattened into pads; flowers occur along the edges of the pads. These, and many other cacti, have edible fruits known as tunas. Other members of the same genus (Opuntia) have elongated, cyclindrical stems and are known generally as cholla or cane cacti. The barrel cacti normally consist of a single, corrugated body. Smaller and without the corrugations are such cacti as the hedgehog cacti. Pincushion cacti are aptly named.
Fabaceae: Pea Family. second largest family of plants, with some 18,000 species. All have in common the type of fruit known as a legume; this is a pod-structure that splits along two sides, with seed attached along one or both seams. Numerous plants important economically belong to this family, providing food (e.g., beans, peanuts), ornamental plants (e.g., Acacias), fodder (clover, alfalfa), and commercial chemicals (dyes, tannins). Legumes generally are associated with bacteria that live in nodules on the roots; these bacteria fix atmospheric nitrogen into forms usable by plants, and often legumes such as alfalfa are planted as organic fertilizer; this is particularly important in desert regions, where the low level of usable nitrogen often is a limiting factor. Kudzu is an introduced vine that wreaks havoc in the southeastern USA. Honey Mesquite is a major component of the desert. Its nutritious beans are utilized by many desert animals - Screwbean Mesquite (Tornillo), prefers floodplain habitat. Various species of acacia occur throughout the desert. Retama (Parkinsonia aculeata) is an introduced species [that is] at home along arroyos. Mescal Bean (Mountain Laurel) is common in limestone areas
overloaded with grazing stock. With a combination of overgrazing and drought, much of the grasslands were degraded into Chihuahuan Desertscrub
Onagraceae: Evening Primrose Family. bloom in the evening through the night, but soon wilting in the light of day .. Baja Evening Primrose
Sapindaceae: Soapberry Family. Western Soapberry .. Mexican Buckeye ..plants sometimes placed in the family are the maples (Acer).
Zygophyllaceae: Caltrop Family. Creosotebush, Larrea tridentata reached its dominant position in what once were desert grasslands when overgrazing and drought knocked down grass .. Creosotebush. Thanks to its noxious chemical makeup, it is largely immune to herbivorous attack. one of the dominant shrubs
Tamaricaceae: Tamarix Family. Salt Cedar as invaded virtually all of the waterways of much of the West, the Southwest, and northern Mexico .. Tamarisk is highly tolerant of both salty and alkaline condition. It tends to crowd out native species from the floodplain while supporting little in the way of wildlife .. transpires enormous amounts of water from rive-maintained ground water
Solanaceae: Potato Family. Silverleaf Nightshade. Tobacco is a prominent member of the family and includes wild species in the desert .. Sacred Datura ..
Fouquieriaceae: Ocotillo Family. Ocotillo .. oothills or other areas of rough topography. It's noted for its ability to drop it leaves during periods of drought and very quickly grow a new crop when wetter conditions return.
Cucurbitaceae: Gourd Family. widely utilized by wildlife and, in the past, by American Indians.
Lamiaceae: Mint Family. large number of species .. Mexican Blue Sage.
Salicaceae: Willow Family. The willows and cottonwoods .. water and the original bosques that crowded the floodplains of the Rio Grande had both as prominent members. The Coyote Willow
Scrophulariaceae: Figwort Family. genus Leucophyllum are widely planted as drought-resistant shrubs that bloom profusely several times during the hot season. Penstemon.
Bignoniaceae: Catalpa Family. The Desert Willow is a prominent, small tree along desert drainageways .. Yellow Bells
Asteraceae: Sunflower Family. along with the Fagaceae and Cactaceae, tends to dominate the Chihuahuan Desert. Tarbush. Members of the genus Parthenium are widespread; Parthenium confertum has been used as a source of latex and was attempted to be raised for rubber during the second world war. Artemisia filifolia (Sand Sagebrush) is a prominent shrub in areas with a sandy substratum. The Desert Marigold .. Turpentine Bush. Firewheel, Gayfeather, and Mexican Hat (Cone Flower)
Poaceae: Grass Family. Black Grama is the common grama grass of the desert grasslands, Hairy Grama
Agavaceae: Agave Family. agaves, yuccas, sotols, and bear grasses .. agave Lechuguilla (Shindagger) often is considered as a marker for the Chihuahuan Desert.
*Pinaceae: Pine Family
Apache Pine Pinus engelmannii
*Agavaceae: Agave Family
*Lechuguilla Agave lechuguilla
*Torrey Yucca Yucca torreyi
*Sotol Dasylirion wheeleri (genus only)
*Asteraceae: Sunflower Family
*Chocolate Daisy Berlandiera lyrata
Turpentine Bush Ericameria laricifolia
Fleabane Daisy Erigeron divergens
*Mexican Hat Ratibida columnifera
Bignoniaceae: Catalpa Family
*Desert Willow Chilopsis linearis
*Yellow Bells Tecoma stans
*Cactaceae: Cactus Family
*Barrel Cactus Ferocactus wislizenii
*Prickly Pear, Cholla Opuntia sp. (genus only)
*Fabaceae: Pea Family
*Viscid Acacia Acacia neovernicosa (genus only)
*Guajillo Acacia berlandieri (genus only)
*Honey Mesquite Prosopis glandulosa
*Retama Parkinsonia aculeata
Fagaceae: Beech Family
*Scrub Oak Quercus turbinella (genus only)
Fouquieriaceae: Ocotillo Family
*Ocotillo Fouquieria splendens
Lamiaceae: Mint Family
*Cherry Sage Salvia greggii (genus only)
*Malvaceae: Mallow Family
Wild Cotton Glossipium thurberi
*Onagraceae: Evening Primroses
Baja Primrose Oenothera stubbei *family only
Rosaceae: Rose Family
*Apache Plume Fallugia paradoxa
*Rosewood Vauquelinia sp.
Salicaceae: Willow Family
*Willow Salix sp.
*Cottonwood Populus sp.
Sapindaceae: Soapberry Family
*Western Soapberry Sapindus saponaria
Scrophulariaceae: Figwort Family
*Rain Sages Leucophyllum sp.
*Penstemon Penstemon sp.
Tamericaceae: Tamerisk Family
*Salt Cedar Tamerisk sp.
Zygophyllaceae: Caltrop Family
*Creosotebush Larrea tridentata
invertebrate animals far greater than those of vertebrates.
Gastropoda (literally, stomach foot) includes the snails and slugs.
Metcalf and Smartt (1997) note that the open grassland and scrub of the desert support relatively few snails. Many of those that are present are small to minute. Mountain ranges in the northern desert have a more diverse gastropod fauna. and many have endemic species (species that occur nowhere else). The dry season usually is spent in aestivation: a dormant state similar to hibernation in vertebrates. shell is sealed by secretions that act to slow desiccation. With the end of the dry season, the snail reactivates.
Class Malacostraca: order Isopoda (wood lice) .. Socorro isopod endangered species lives only in one spring-fed area near Socorro, New Mexico. [like pillbug]
Class Branchiopoda: Triops. Triops lives in temporary pools that form during the rainy season. Eggs remain viable for many years with embryonic development held in stasis (diapause) until water once more is available, thus allowing the creatures to outlast droughts. One of the species of Triops is claimed to be the oldest living species at about 200 million years.
Decapoda (10 feet) .. crayfish (crawdads). Several species, including introduced species that may threaten freshwater communities. crayfish, Cambarellus chihuahuae, occurs only in Chihuahua, west of Villa Ahumada.
symbols of the desert: sand dunes, saguaros, rattlesnakes, and scorpions. Scorpions and related forms, including spiders, pseudoscorpions, daddy longlegs, and solpugids, do well in the desert as do the more distantly related centipedes and millipedes.
Millipedes are considered harmless if somewhat stinky when disturbed; centipedes have a pair of claw-like structures under the head that have poison. The larger of our desert centipedes may give painful bites but are not considered dangerous to humans
Araneae (spiders), Pseudoscorpionida (book scorpions, false scorpions, and pseudoscorpions), Scorpiones (scorpions), and Solpugida, also known as Solifugae (solpugids and sun spiders), and the Uropygi (vinegaroon). There are other chelicerates
Spiders are common in the desert. All are venomous, but relatively few are dangerous to humans .. genus Loxosceles, which includes the Brown Recluse Spider .. Widow Spiders (Lactrodectes hesperus), the western equivalent of the Black Widow Spider .. Tarantulas probably are considered by most to be the spider of the deserts. Although popular mythology has them as being deadly, tarantulas, like most spiders, are slow to bite. Although a bite may be painful, the venom is not considered dangerous to humans.
pseudoscorpions are an inconspicuous group with probable minimal impact on the environment
scorpions the small Centruroides is the danger
Vinegaroons (also known as whip scorpions) are common .. other than being able to give a hearty pinch and a spray of acetic acid (otherwise known as vinegar), they are harmless, and unless they feel threatened, can be handled with care.
Solpugids, often call sun spiders .. basically harmless to humans, and some people allow them to remain in a residence to help keep down insect vermin.
insects are the largest and most successful of the terrestrial animal taxa.
Coleoptera (beetles), huge group , predators, others herbivores, and the dung beetles even utilize feces as food for their young
Diptera (flies), common house fly , mosquitos, robber flies, and crane flies... to mention only a few ,
Hymenoptera (ants, bees, wasps), wide variety of ants, bees, wasps, and hornets ,
Lepidoptera (butterflies and moths), butterflies
Orthoptera (grasshoppers and relatives). cricket, Stenopelmatus, often known as Jerusalem Crickets, but in the Chihuahuan Desert more commonly as Niña de la Tierra (Child of the Earth).
Osteichthyes: Bony Fish, widely scattered geographically, with low biodiversity , restricted to the Rio Grande, Rio Pecos, and Rio Conchos along with some tributaries that have permanent or semipermanent water. Springs are the other resource , Both river and spring resources have been reduced because of drought, increased irrigation farming, and development , Edwards et al. (2002:130) note that "Clark Hubbs observed that the Río Sauz went dry in 1947 and no surface waters were available in the river valley (in Miller, 1961). Additionally, at least 30 springs have gone dry in Chihuahua and Coahuila and river discharges of the Río Nazas, Bolson Mayrán, Río Aguanaval, Bolson Viesca, Río de Nadadores, Río Saltillo, Río Salinas, Río del Carmen and the middle Rio Grande are reduced (Contreras-Balderas and Lozano-Vilano, 1994)". Cuatro Ciénegas, as might be expected, has a number of endemic fish (probably 10 of 17 species of Cuatro Ciénegas fishes).
Two orders of the class Amphibia occur: the Urodela (sometimes listed as the Caudata) and the Anura. The former are salamanders and the latter toads and frogs. The salamanders are represented by one species, Ambystoma tigrinum, the Tiger Salamander. As with the other desert amphibians, these salamanders need water for breeding; the eggs are laid in water and the larvae develop in water until they metamorphose into the adult form. Other than in the breeding season, these salamanders may move some distance from water, utilizing rodent burrows and other microhabitats to prevent desiccation.
Bufonidae (true toads) has six species represented; the Hylidae (cricket frogs, tree frogs) has two; the Leptodactylidae (leptodactylid frogs), two; the Microhylidae (narrowmouth frogs), one; the Pelobatidae (spadefoot toads), three; and the Ranidae (true frogs), four.
to protect themselves from desiccation. Some anurans, such as members of the Ranidae, do so by remaining near water so they can easily plop into it when their skin begins to dry (or when predators show up)
rely on microhabitats and behaviors that minimize loss of water. The spadefoot toads, for example, spend a good part of their lives underground, usually coming to the surface only during the rainy season to feed and breed. Breeding is at ephemeral ponds and development may be very rapid, completing metamorphosis before the ponds become dry again.
Testudines (turtles) and Squamata (lizards and snakes)
Most of the turtles are associated with water, but two are not. The Bolson Tortoise (Gopherus flavomarginatus) - limited geographically to the Bolsón de Mapimí
Western Box Turtle also is primarily terrestrial. However, a relative, the Coahuilan Box Turtle, limited to Cuatro Ciénegas, is not, and is the only box turtle that is primarily aquatic.
The aquatic turtles belong to three families: Emydidae (which also includes the terrestrial Western Box Turtle), Kinosternidae (the mud turtles), and the Trionychidae (softshelled turtles). The latter have the shell much reduced and covered with leathery tissue.
Squamata includes the snakes and lizards, which are divided into two suborders (Sauria and Serpentes, respectively).
movability of many of the skull bones in snakes. This loose construction allows engulfing of prey larger than the normal head size of a snake. Snakes also lack eyelids
Most lizards and all snakes are predators.
Seven families of lizards are recorded
Gila Monster is one of only two poisonous lizards [other not in Chihuahuan desert] It barely gets into the Chihuahuan Desert in the northwestern portion near the Arizona/New Mexico border; most of its range is in the Sonoran Desert.
Teiidae is an interesting family of lizards
consist solely of females. The eggs develop parthenogenetically (without fertilization)
suborder Serpentes = 3/4 Colubridae , generally harmless snakes (though capable of drawing blood , desert has a number of venomous species capable of harming humans; such snakes are in the minority, however.
family Elapidae is represented by the coral snakes [eastern/western], seldom seen and seldom aggressive. However, their venom includes a powerful neurotoxin and a bite should be considered as life-threatening and immediate medical aid sought.
more familiar and more often encountered venomous snakes in the region are pit vipers, family Viperidae. Copperhead, Massasauga , five rattlesnakes (the Massasauga usually is considered a rattlesnake, also). The name comes from the presence of a pit between the eyes and nostrils that contains receptors for infrared radiation (heat). Warm-blooded prey can be quite accurately located at close range in complete darkness by this organ. The venom is primarily for capture of prey. The animal is struck by fangs that act as hypodermic needles, injecting venom into the prey. The usual result is the prey animal leaving the scene, only to be overcome by the venom at some point. The snake tracks the victim by olfaction, hanging back until the prey is overcome and unlikely to inflict damage to the snake. The tongue is used as in olfaction, picking up scent molecules from the air and inserting the forked end of the tongue into a sensory structure on the roof of the mouth (Jacobson's organ). As with all snakes, prey items are swallowed whole. .. Although the death rate by rattlesnake bites is low, death can occur, as can tissue damage
birds are relatively well covered in the popular literature.
one of the best known major animal groups
birds, are primarily visual creatures
trongly associated with water. These are the orders Gaviiformes (loons), Podicipediformes (grebes), Pelecaniforms (pelicans, cormorants, and relatives), Ciconiiformes (herons, storks, ibises, etc.) except the Carthartidae (vultures), and Anatidae (ducks, geese, and relatives). As such, these birds occur primarily where water is available. The permanent waterways and reservoirs are the main sites, but other permanent bodies of water are utilized, and temporary waters, such as playa lakes and irrigation drainage ditches, may be utilized by some.
Black Vulture and the Turkey Vulture are common scavengers
California Condor is known from the northern desert region from the latter portions of the Pleistocene Epoch, but there apparently is no historic record.
Falconiformes , Bald and Golden eagles and falcons. The latter includes the Caracara, that does a considerable amount of scavenging , Bald Eagle normally is found in the vicinity of major bodies of water, whereas the Golden Eagle is not so limited in its distribution. Most of the hawks migrate
Galliformes include the various species of quail , Wild Turkey and the introduced Ring-necked Pheasant.
Gruiformes and Charadriiformes generally are associated with water. The former includes cranes, such as the Sandhill Crane and the Whooping Crane , Charadriiformes includes several families; all are associated with water. These include shorebirds and gulls. Although generally associated with rivers and ponds, temporary pools often are utilized and some members may regularly occur some distance from water.
Columbiformes are the doves and pigeons. , very successful group is widespread , Mourning Dove, the Inca Dove, and the White-winged Dove. The Rock Pigeon so common in urban areas throughout the United States is an import from the Old World. A cliff nester in its native habitat, it was preadapted for the buildings in cities. It is limited almost entirely to urban situations.
parrots and relatives are in the order Psittaciformes. Thick-billed Parrots were found in the montane islands of southeastern Arizona and southwestern New Mexico, but must be considered marginal to desert habitat; attempts to re-introduce them are underway. Populations occur in the Sierra Madre Occidental.
Greater Roadrunner , and cuckoos belong to the Cuculiformes: the cuckoo family.
Goatsucker family (Caprimulgiformes) , Nighthawks and Poor-wills are widespread through the desert region are [insectivores, eat on the wing at dawn/dusk]
Apodiformes , swifts and the hummingbirds , common throughout the desert region, both as summer residents and as migrants. ,
Kingfishers, order Coraciiformes, are limited strictly to waterways that provide their main diet of small fish.
Piciformes (woodpeckers) is a very successful order that occurs throughout , large shrubs or trees. They are insectivores, though the sapsuckers also feed extensively on tree sap
Tyrannidae, or tyrant flycatchers, includes many desert inhabitants
Laniidae is represented in the desert region primarily by the Loggerhead Shrike
Corvidae , rows, ravens, jays, and magpies. Ravens and several species of jays are common desert dwellers. The Chihuahuan Raven is common throughout the region, with jays commoner in brushy and woodland habitats. Members of the family are considered to be among the most intelligent of the birds.
Wrens, order Troglodytidae, are common birds throughout the desert; , Cactus Wren , Mimidae includes mockingbirds and thrashers, Northern Mockingbird
Most of the sparrows fall into the family Emberizidae, and a large number occur in the Chihuahuan Desert (32 species have been recorded from the El Paso area, for instance). These birds are specialized as seed eaters.
Fringillidae) include the goldfinches, Evening Grosbeak, and the familiar House Finch
Passeridae: House Sparrow. This introduced species (long known as the English Sparrow) , Starling (family Sturnidae)
only marsupial in the Chihuahuan Desert is the Virginia Opossum (Didelphis virginiana).
Most shrews occur in northern and north-temperate zones that are well watered. In the Southwest, most species occur in the better watered mountains. The Desert Shrew (Notiosorex crawfordi), however, is arid adapted and occurs in the Chihuahuan Desert (the type locality is El Paso, Texas)
Bats are members of the order Chiroptera (literally, hand wing
Bat are the only flying mammals,
mammalian orders; the Chiroptera is the second largest
Bat are excellent flyers, but owe control of the night skies largely to their highly developed sense of echolocation.
various facial decorations that give so many bats character for the most part appear to be adaptations involved in echolocation
Although we tend to think of bats as feeding on insects (and indeed, many do), their ecological niches are far broader than that. Various species feed on nectar (that is, they are nectivorous) and pollen, on fish (piscivorous), on small vertebrates (carnivorous), on fruit (frugivorous), and on blood (sanguivorous)
Most of the bats people encounter in the United States are insectivorous, but in the southern Southwest and south into Mexico, other types appear. - tropics are the strongholds of the order
Ghost-faced Bat (Mormoops megalophylla) - Mormoopidae
Phyllostomidae by three species [in chihuahuam desert]. are nectivorous and important as pollenators of agaves in our region. Such bats are characterized by relatively weak dentition, long snouts, and long tongues.
Vespertilionidae - At least 17 species are found in the Chihuahuan Desert. All are insectivorous - any hunt flying insects, while the gleaners tend to pick prey items from surfaces such as leaves. Several species usually are found feeding over large bodies of water. The Pallid Bat will attack scorpions and centipedes on the ground.
Mexican Free-tailed Bat (Tadarida brasiliensis) forms huge maternity colonies, up to a number of millions of individuals. The colony at Carlsbad Cavern National Park is the best known
almost wiped out by pesticides, and the Carlsbad bats are greatly diminished in number. As with many predators, contaminents in the bodies of their prey become concentrated in the predator with drastic results.
order Carnivora includes the families Canidae (wolves, foxes), Ursidae (bears), Procyonidae (raccoons and relatives), Mustelidae (weasels, badgers, and relatives), Mephitidae (skunks), and Felidae (cats).
Five canids occur in the Chihuahuan Desert (ignoring the domestic dog). Wolves (Canis lupus) now are extirpated, but Coyotes (Canis latrans) is common throughout. The common fox of the mountains and other areas of rough topography is the Gray Fox (Urocyon cinereoargenteus). This is a good climber and occasionally may be found in trees as well as in precipitous rocky areas. Out in the desert basins, the Kit Fox (Vulpes macrotis) is the common fox - Red Fox (Vulpes vulpes) is extremely marginal in the north.
Black Bear (Ursus americanus) occurs primarily in mountain ranges in the Chihuahuan Desert region, but may wander into other habitats on occasion. The Grizzly Bear Ursus arctos) was common in parts of the region but is now extirpated.
Procyonidae occur. The Ringtail (unfortunately often called Ringtail Cat) is Bassariscus astutus. Much more svelte and nimble than the Raccoon, it is at home in trees and rocky areas. Ringtails tend to be somewhat more carnivorous than its relative, the Raccoon. Raccoons are common now, at least in the northern desert region, along major drainageways and in montane forest. It seems to thrive best in the region where it can freeload to some degree on human garbage and crops. It's absent from the desert fossil record, athough occurring to the east and on the West Coast; it may have entered the desert region when humans opened up a "garbage" niche. The last member of the family is the Coati. This large member of the family usually travels in bands of up to well over a dozen individuals. The U.S. portion of the desert is marginal,
Mustelidae: the Long-tailed Weasel (Mustela frenata) and the Badger (Taxidea taxus - Weasels are built to go into burrows after prey, and as a group show adaptations in size for particular size classes of prey (or perhaps particular size classes of burrows) - Badger isn't built to go into a burrow after its prey. Rather, it's built to dig them out. Powerful forelimbs and front claws are well adapted for this. It's habitat is extremely wide, from lower desert to timberline areas farther north.
Mephitidae. Four species occur through much of the area. Most common in most places is the Striped Skunk (Mephitis mephitis). The Western Spotted Skunk (Spilogale gracilis) is generally less common, but widespread. Another species of Mephitis, M. macroura (Hooded Skunk) is rare along the U.S./Mexico boundary, but widespread to the south. Finally, the Hog-nosed Skunk (Conepatus leuconotus) occurs throughout the region.
Felidae is made of the cats - Bobcat (Lynx rufus) and Mountain Lion (Felis concolor) are found throughout. The Jaguar (Panthera onca) is marginal on the east and west, but seems to be increasing its presence in part of its original range along the Arizona/New Mexico border. The Ocelot (Felis pardalis) is more problematical, but may occasionally enter the desert region near Big Bend.
Tayassuidae consists of the peccaries, of which the Collared Peccary (Pecari tajacu) is the species in our area. The Cervidae is the deer family, with White-tailed Deer (Odocoileus virginianus) and Mule Deer (Odocoileus hemionus) associated with the desert. Elk (Wapiti, Cervus elaphus) were native in some of the northern desert mountains such as the Guadalupes; extirpated by overhunting, they now have been reintroduced from more northern populations. The Pronghorn (Antilocapridae, Antilocapra americana... often called antelope,
Bovidae includes, marginally in our area, the American Bison (Bos bison) and not-marginally, the Bighorn (Mountain) Sheep, Ovis canadensis. Populations of the latter still occur in the San Andres Mountains of southern New Mexico and in the Big Hatchets (and into Mexico) in the extreme southwest of New Mexico.
ot native. Feral pigs (Sus scrofa, family Suidae) are widespread. Barbary Sheep, or Aoudad (Ammotragus lervia), has spread from areas where it was introduced as a game animal into at least the margins of the desert. Domestic stock that have had severe effects on the desert include cattle (Bos taurus), sheep (Ovis aries), and goats (Capra hircus). Overgrazing, in combination with drought, has degraded much of the desert grassland into scrub desert.
ground squirrels (Spermophilus... literally, seed lovers), Black-tailed Prairie Dog (Cynomys ludovicianus), and antelope squirrels (Ammospermophilus). [most primitive rodents]
Ground squirrels use burrows for protection, but feed on the surface. Like most sciurids, they are diurnal, retreating to their burrows at night (most other desert rodents are crepuscular... active at dusk and dawn... to nocturnal). A variety of foods are eaten, including green fodder, seeds, nuts, insects, and even meat.
Black-tailed Prairie Dog is a moderately large squirrel living in colonies where there is deep, mostly rockless, soil. Limited pretty much to grasslands at the higher elevations in the desert, they feed extensively on leafy material. They have been reduced to a small proportion of their original numbers by intentional poisoning.
Spotted Ground Squirrel (S. spilosoma, Mexican Ground Squirrel (S. mexicanus), and Rock Squirrel (S. variegatus.
Pocket gophers, family Geomyidae ("earth mice", literally) are fossorial animals, meaning they spend most of their lives underground in burrow systems ... Feeding is primarily on the underground parts of plants, though they may open a tunnel to the surface and, keeping next to the opening, gather plant food from the immediate vicinity. They tend to be very antisocial, with one animal per tunnel system except during the reproductive season
Four species of pocket gophers occur in the Chihuahuan Desert. Generally speaking, the Yellow-faced Pocket Gopher (Cratogeomys castanops) lives in relatively deep, tight soils, whereas the Desert Pocket Gopher (Geomys arenarius) prefers sandy soils. ... Botta's Pocket Gopher (Thomomys bottae) is limited to the shallow, rocky soils of the desert mountains ... Southern Pocket Gopher inhabits the shallow rocky soils of the higher mountain ranges from southwestern New Mexico and adjacent Arizona south.
Heteromyidae includes the pocket mice and kangaroo rats .. center of diversity in the Southwest and Mexico. Eleven species are known from the Chihuahuan Desert; these can be divided into the spiny-rumped pocket mice (Chaetodipus), silky pocket mice (Perognathus), and kangaroo rats (Dipodomys). All feed primarily on seeds ... kangaroo rats tend to forage into open areas where they are particularly vulnerable to owl predation. Their middle ear chambers are greatly enlarged, allowing them to pick up the very faint, low frequency sound made by an attacking owl's wings when it brakes while reaching its talons for its prey; a split-second panic jump on the part of the rodent may (or may not) save it.
Some of the kangaroo rats are so adapted for arid conditions that they are able to survive solely on metabolic water while feeding on dry seeds (that doesn't mean they like it... only that they can do it when necessary).
Beavers (family Castoridae, Castor canadensis) are limited to the water courses of the larger streams and rivers. With the shallow, fluctuating waters of Southwestern rivers, the classic building of dams and lodges is not practical; instead, dens are excavated into river banks, the entrance opening under water. Feeding is on the bark of willows and other riparian growth.
Old World House Mouse (Mus musculus), Roof Rat (Rattus rattus), and Norway Rat (Rattus norvegicus) ... House Mouse and Roof Rat occurring around human habitations in the desert.
Neotominae includes the bulk of the Chihuahuan Desert cricetids. Most of these fall into groups known commonly as woodrats (or packrats), white-footed mice, grasshopper mice, and harvest mice.
occurrence in the eastern U.S. The White-throated Woodrat (N. albigula) is widespread west of the Rio Grande and south in Mexico west of the Rio Conchos.
present to the east; this is the Eastern White-throated Woodrat, N. leucodon.
Southern Plains Woodrat (N. micropus), they tend to remain in desert mountains and outcrops of rocky terrain; in areas without N. micropus, which is most of the desert except the northern part and the extreme eastern margin, they will inhabit both habitats. Both species usually build houses of sticks, etc., around the base of bushes when building out in the basins.
relatively small Goldman's Woodrat (N. goldmani) ... poorly known apparently occurring south of the border in Chihuahua and Coahuila
Mexican Woodrat (N. mexicana) occurs throughout the region, but usually in higher elevations (pinyon-juniper and higher);
Grasshopper mice (Onychomys) ... Northern Grasshopper Mouse (O. leucogaster) enters the northern part of the Chihuahuan Desert and also occurs along the eastern edge; its range extends far to the north in the U.S. Mearns Grasshopper Mouse (O. arenicola) is primarily Chihuahuan Desert, though extending somewhat beyond its western and eastern boundaries and far beyond to the south.
White-footed mice (Peromyscus) ... P. eremicus tends to occur in rocky hillside habitats or sand-dune habitats; P. leucopus in rather heavily vegetated arroyos; P. boylii in the vicinity of oaks in the mountains; and P. nasutus in the highest elevations of the Franklins. Peromyscus maniculatus seems to slip in wherever a space is left open by the other species
harvest mice (Reithrodontomys) ... Western Harvest Mouse (R. megalotis) is the common species, with R. montanus rare in grasslands in the northern Chihuahuan Desert.
lower elevations are inhabited by the Hispid Cotton Rat (Sigmodon hispidus), while the Tawny-bellied Cotton Rat occurs in the western portions, but not east of the Rio Grande. In highland areas from southwestern New Mexico and southeastern Arizona and from the Guadalupe and Davis mountains south, the Yellow-nosed Cotton Rat S. ochrognathus occurs. ...
Meadow Vole has a relictual population in northern Chihuahua
Muskrat (Ondatra zibethicus) essentially is an overgrown semi-aquatic vole. It inhabits drainage ditches and quiet areas of the Rio Grande.
Porcupine (Erethizon dorsatum, family Erethizontidae) 2nd largest rodent to beavers, This species is widespread in northern North America from Alaska to Labrador and south in the western U.S. into the northern Chihuahuan Desert. Although most common in the sky islands of the arid lands, it does get down into creosotebush desert.
Lepus californianus, the Black-tailed Jackrabbit, and L. callotis, the White-sided Jackrabbit. The latter is basically marginal to the western desert, generally being elevationally higher than true desert. The Black-tailed Jackrabbit, however, is common throughout the desert region.
Desert Cottontail (S. audubonii) is widespread throughout the desert lowlands
The second species may actually be several species and are marginal, occurring at generally higher elevations. These have been considered to belong to the Eastern Cottontail (S. floridanus), but there is no consensus as to what species or how many species are involved.