Southwest Deluge

Over the past week, a deep atmospheric trough off the West Coast directed heavy rain and high winds across Northern California, Oregon and Washington.  Then, its southern portion split away and strengthened off the coast of Southern California; this "cut-off low" is now sweeping torrential rain across San Diego, Los Angeles and the adjacent mountains.

Prolonged, heavy rain will be especially problematic in the burn scar areas, likely producing mudslides and landslides.  On the positive side, the Southern Sierra Nevada may receive up to three feet of snow, a welcome, early addition to the vital winter snow pack.

After pummeling Southern California, the storm is expected to move across western Arizona and southern Nevada before dumping significant snow in the mountains of Utah and Colorado.  Unfortunately, a second Pacific storm system may form in its wake, augmenting the potential for widespread flooding across the arid landscapes of the Desert Southwest.

Desert Southwest Flooding

Copious moisture from tropical systems off the coast of northwest Mexico has spread northeastward into the Desert Southwest.  Flooding has occurred, and will continue to develop, across Arizona, southern Nevada, Utah, New Mexico and Colorado.  Some of that tropical moisture is expected to reach Metro Denver this morning.

Up to five inches of rain is expected across southern Arizona and daily precipitation records have occurred from that region to Grand Junction, Colorado (including a record 0.92 inch in Las Vegas).  What may seem to be rather meager totals for those of us who live in other areas of the country are not readily absorbed in desert terrain, leading to rapid runoff and flash flooding.

Fueled in part by a deep atmospheric trough over the Desert Southwest, the moisture flow will likely continue for another 48 hours and normally dry creeks and washes may become raging torrents.  Hopefully, those who live along those drainage channels will heed Weather Service warnings. 

Westward from Flagstaff

Leading westward from Flagstaff, Arizona, Interstate 40 passes through a scenic landscape of meadows and ponderosa pine forests.  Beyond Williams, the highway leaves this lofty terrain and descends into a broad swath of open parklands and low ridges; covered by juniper shrubs; this attractive ecosystem generally ranges in elevation from 3000 to 4000 feet.

Nearing Kingman, the highway drops further into the bleak landscape of the Mojave Desert, bordered by high but treeless ranges.  Three hours later, during which we crossed the Colorado River south of Needles, California, we finally escaped the Mojave west of Barstow; we then followed Interstate 15 westward to Cajon Pass and descended into the Los Angeles basin.

One cannot fully appreciate the dimensions and severity of a desert without driving across it; even today, with our modern, air-conditioned vehicles, it is a tiring experience.  We can only begin to imagine the challenges endured by those who used horses and wagons to make the journey. 

An Island of Greenery

Heading to California for my son's wedding, we left Denver early yesterday morning, driving south on Interstate 25.  Once we crossed Raton Pass, on the Colorado-New Mexico border, trees and other greenery was limited to the stream and river channels.

The landscape was especially dry after we passed Santa Fe and descended to Albuquerque.  There we switched to Interstate 40 and headed west, undulating through scrub grasslands broken by rock outcrops and low mesas; only the bulk of the Mt. Taylor massif, north of Grants, towered above the arid terrain.  Crossing into Arizona, streams were limited to shallow washes and the Little Colorado River, which cut a deep channel through the high desert landscape.  Then, fifty miles from Flagstaff, a cluster of mountains appeared on the western horizon, our first glimpse of the volcanic San Francisco peaks.

Within a few miles of the city, piñon pine woodlands spread along the highway and, once in Flagstaff (elevation 6909 feet), taller ponderosa pines adorned the meadows and suburbs.  Indeed, sitting along the southern edge of the highlands, the city is a welcome island of greenery in the Desert Southwest; we stopped to enjoy a meal, walk through the historic district in a cool, light mist and spend the night.

Excessive Heat in the West

Excessive heat is plaguing most of the Western U.S., severely exacerbating the severe drought across the region.  While afternoon temperatures approaching or exceeding 110 degrees F are not unusual in the Desert Southwest, that area is expecting highs near 120 degrees.  Furthermore, afternoon highs as far north as Montana will approach or exceed 100 degrees in the coming days.

Here along the Colorado Front Range, we are expected to reach 100 degrees the next few days, under intense sunshine; fortunately, our elevation, combined with the dry air, will enhance radiative cooling at night, providing some relief as the temperature falls into the mid sixties.  Furthermore, the Continental Divide is a focus for thunderstorm development, offering spotty and transient relief for some towns and cities as the storms drift eastward.

A persistent atmospheric ridge is responsible for the excessive heat, diverting cold fronts and Pacific moisture into Canada.  By next weekend, that ridge is expected to break down, withdrawing toward the Desert Southwest; then, those of us in the northern and eastern regions of the American West can expect more seasonable conditions.

Rain, Snow & Wildfire

Over the next few days, light to moderate rain will fall across the Sonoran and Chihuahuan Deserts of the American Southwest, bringing some relief to the ongoing drought in those areas.  Across the higher terrain of Northern Arizona and New Mexico, the precipitation will fall as snow.

The benefactors for this scenario are a deep atmospheric trough across the Western U.S. and a "cutoff low" (i.e. not associated with a front) off the coast of Northwest Mexico.  This low, spinning counterclockwise over the Pacific will sweep in moisture from both the ocean and the Gulf of California.  Farther east, the southern edge of the trough will angle to the northeast, igniting showers and thunderstorms across Texas and the Gulf Coast States.

Meanwhile, high pressure over the Great Basin, interacting with the cutoff low, will send strong Santa Ana winds through the canyons of Southern California, increasing the risk for wildfires.  In effect, the same atmospheric conditions may produce beneficial and destructive results in two adjacent geographic areas. 

A Tardy Southwest Monsoon

Monsoon thunderstorms generally begin to develop across the Desert Southwest by mid July, spreading northward over the following month.  In desert areas, the storms bring welcome rain but often cause flash flooding and haboobs (dust storms).

This year, persistent high pressure over the Desert Southwest has produced relentless sunshine and oppressive heat; it has also shut off the monsoon flow.  By mid summer, high pressure over the Southern Plains usually combines with low pressure over the Baja region to sweep in moisture from the Gulf of Mexico and the Sea of Cortez, igniting the storms.  There is some evidence this week that the high pressure dome over the Southwest is finally shifting eastward, allowing the humid monsoon winds to enter the Sonoran and Chihuahuan Deserts.

While the Southwest Monsoon generally reaches the Colorado Front Range during the second half of August, we have been receiving regular, late-day thunderstorms throughout July.  These storms, in part, have resulted from the persistent high pressure over the Desert Southwest, which has shunted Pacific moisture to the north of the Four Corners region.  Stagnant weather patterns often benefit one geographic area at the expense of another.

Southwest to the Four Corners

Looking ahead to several days with no commitments, I have decided on a road trip to the Four Corners region, where the States of Colorado, New Mexico, Arizona and Utah meet.  Though I have been to that area in the past, there are several routes through its varied landscape that will give me a new perspective on the terrain and topography.  Now that we have entered the summer tourist season, I will skip Mesa Verde National Park which I had the pleasure to visit almost thirty years ago.

Geologically, the Four Corners is a land of volcanic features, superimposed on uplifted and eroded late Paleozoic and Mesozoic sediments.  Tributaries of the Colorado River drain the landscape; the San Juan rises from numerous rivers and creeks along the south flank of the the San Juan Mountains and then heads westward to join the Colorado in Lake Powell while the Dolores River drains the west flank of both the San Juans and the Uncompahgre Plateau as it flows NNW to merge with the Colorado northeast of Moab, Utah.  Other prominent natural features include Ship Rock (a remnant volcanic neck), Sleeping Ute Mountain, the  La Sal Range (east of Moab) and the Chuska Mountains (on the New Mexico-Arizona line).

Planning to leave Denver early tomorrow morning, I will follow U.S. 285 southwest, crossing Kenosha Pass to drop into South Park.  From there, the highway crosses Trout Creek Pass to enter the Upper Arkansas River Valley and then turns southward, climbing over Poncha Pass to reach the broad San Luis Valley.  Within that valley I will switch to U.S. 160, heading west and then southwest, climbing along the South Fork of the Rio Grande River to Wolf Creek Pass.  Beyond that pass, a long descent will take me through Pagosa Springs and into Durango, where I will likely spend the first night.  More details in coming posts.

See also: San Juan Volcanism

Western Heat Wave

Intense heat is beginning to develop across the Desert Southwest and will spread northward through the Great Basin and Central Valley of California; before it's over, the Pacific Northwest will also be enveloped in the swath of hot air.

The culprit is an atmospheric ridge, a northward bowing of the jet stream along the outer rim of a high pressure dome.  Within the ridge (beneath the dome), sinking air heats up and dries out and cloud formation is impaired; Santa Ana winds may also develop in Southern California.  Triple-digit heat is forecast for much of the region, with upper 90s (F) expected in Oregon and Washington.  Meteorologists warn that the high pressure ridge will remain in place through the upcoming weekend.

As one might expect, the Western heat wave is tied (meteorologically) to the Texas floods.  East of the ridge, the jet stream dips southward and this trough has spawned an upper level low over central Texas.  Counterclockwise winds around the low are combining with clockwise winds around a high pressure dome over the Southeast, pulling copious Gulf moisture across East Texas, Louisiana and the lower Mississippi Valley.  Once this atmospheric pattern shifts eastward, the flooding rains in Texas will cease and the Western heat will abate.

The Blanca Monsoon

Blanca, initially a hurricane off the coast of the Baja Peninsula, has moved into the Desert Southwest as a Tropical Depression, bringing copious moisture to Southern California, Arizona and New Mexico.  In many ways, this moisture flow mimics the annual Southwest Monsoon, which generally begins by mid summer and brings flooding rains to the Southwestern Deserts and Four Corners region; by late July or August, the monsoon moisture reaches the Colorado Front Range, igniting late afternoon thunderstorms.

Blanca's moisture will reach Colorado as well, interacting with an atmospheric trough that is dropping through the High Plains; as a result, cloudy, cool and rainy weather is forecast for later this week.  Fortunately, the disruption of sunshine will be brief; unfortunately, Blanca's remnants will aggravate flooding across the Platte River watershed.

Though moisture from Blanca will produce limited benefits in California, where an intense drought persists, it is not unusual for hurricanes and tropical storms to put an end to droughts across the Southern Plains and Southeastern States, especially when blocking highs or stationary fronts slow their movement.  Indeed, when it comes to rain-making, there's nothing like the deep moisture of a tropical system.

Southwest Monsoon in January

The Southwest Monsoon, bringing welcome rains to the Desert Southwest, occurs in summer each year, though its intensity and extent often varies.  The nourishing rains and thunderstorms develop as moist air is swept in from the Sea of Cortez and the Gulf of Mexico by winds generated between low pressure over southeastern California (or the Upper Baja) and high pressure over the Southern Plains.

Such an atmospheric scenario is currently developing in that region and thunderstorms are expected to rumble across the deserts of Arizona and New Mexico over the next few days; unlike the summer monsoon, this weather pattern will bring snow to the higher elevations of the Four Corner States, especially in northern Arizona, New Mexico and southern Colorado.

While the summer monsoon brings vital moisture to these dry lands and this week's storms will augment the region's snowpack, the current "monsoon" may also douse some of the revelry over Super Bowl Weekend (held in Phoenix this year).  Apparently, Mother Nature is not a football fan.

The Gila River

Covering more than 58,000 square miles, the watershed of the Gila River includes most of Arizona south of the Mogollon Rim.  The river itself rises on the west side of the Continental Divide in western New Mexico; flowing westward into Arizona, it receives the waters of the San Carlos River within the San Carlos Reservoir, northwest of Mount Turnbull.  Continuing westward, the Gila takes in water from the San Pedro River (flowing north from Mexico), flows south of Chandler, Arizona, and then angles northwestward, passing between South Mountain and the Sierra Estrella, just south of Phoenix.  In southwest Metro Phoenix, it merges with the Salt River; the latter courses westward through the heart of the city after gathering flow from numerous tributaries that drop from the edge of the Mogollon Rim (among these are the Verde, White and Black Rivers and Canyon Creek).

Just west of its junction with the Salt, the Gila receives the waters of the Agua Fria, which rises east of Prescott and flows southward through western Metro Phoenix; en route, the Agua Fria is dammed to form Lake Pleasant.  Below the mouth of the Agua Fria River, the Gila dips southward, passing Gila Bend, and then enters Painted Rock Reservoir; beyond that reservoir, it continues westward through low desert terrain, joining the Colorado River at Yuma, Arizona. At its mouth, the Gila has flowed 650 miles and dropped 5500 feet from its source in the Gila National Forest of New Mexico.

As one might expect in the Sonoran Desert, flow volumes through the Gila River and its tributaries are highly seasonal, fed primarily by the monsoon rains of summer, by mountain springs and by winter snows across the Mogollon Rim.  Reservoirs along the Gila, while providing irrigation for agriculture in its valley, have all but eliminated its contribution to the Colorado, further ensuring that America's great western river will never again reach the sea (unless, of course, human civilization fails and our massive dams succumb to the Colorado's untamed torrent).

The Goose Duck

Black-bellied whistling-ducks are permanent residents of South America, Central America, Mexico and southern Arizona and have long been summer residents in eastern Texas, Louisiana and southeastern Arkansas; in recent years they have become permanent residents of central Florida and have been expanding their range throughout the State and into other Southeastern States.

These tall, colorful ducks usually nest in tree cavities but may lay their eggs (up to 16) directly on the ground; in either case, little nest preparation is undertaken and females may lay eggs in one another's nests.  Unlike most other ducks, these whistling-ducks often perch in trees or on fences and, like geese, are monogamous; also like geese, males and females have the same plumage and share parenting duties.  Once established in an area, black-bellied whistling-ducks tend to be rather tame and, like Canada geese, seem to have a fondness for golf courses, where they may gather in large flocks.

Primarily herbivorous, these lanky ducks feed on a wide variety of foliage and seeds but may also consume insects and other small invertebrates; natural predators include snakes, raccoons, fox, coyotes, hawks and owls.  While many bird species are threatened by habitat loss due to development and agriculture, it is refreshing to learn that such an attractive duck has adapted well to man's assault on natural ecosystems.

Mountain Plovers

The only thing "mountain" about mountain plovers is that they summer and breed in the Mountain Time Zone.  Preferring short-grass prairie and other flatlands with sparse vegetation, they nest on the High Plains, from southernmost Canada to eastern New Mexico and West Texas; small populations have also been found in Utah.

Soon after arriving on the High Plains in spring, mountain plovers pair off and scoop out a number of shallow depressions, one of which is eventually used for the nest.  As with most "shorebirds," the young are active soon after hatching and hunt for insects with their parents.  Those hoping to encounter mountain plovers are advised to drive along graveled country roads of the High Plains, especially in the National Grassland areas; since they prefer sparse vegetation, these birds are often best found in and around prairie dog colonies.  Rather tame, they seldom fly off as your vehicle approaches, preferring to run away or flatten themselves against the stark terrain to avoid detection; among their natural enemies are prairie falcons, Swainson's hawks, swift fox, coyotes and rattlesnakes.  Challenged by loss of prairie habitat, mountain plovers have adapted to the presence of cattle (surrogates for the great bison herds) and are not officially listed as a threatened species by the U.S. Fish & Wildlife Service.

Come fall, mountain plovers head for wintering grounds in the valleys of California or in desert grasslands of southern Arizona, northern Mexico or West Texas; those that breed in southern regions of the High Plains may not migrate if insects and other terrestrial invertebrates remain available.  Since they tend to wander about during the autumn migration, it is then that they may turn up in unexpected habitat or distant from their usual range.

Eolian Jurassic Sandstones

Three eolian (wind-deposited) Jurassic sandstones make a major contribution to the spectacular scenery of the Colorado Plateau.  These strata, initially emplaced as dune fields, have compacted into unique sedimentary rocks, cemented by heat and pressure over more than 150 million years.

The oldest of these is the Wingate Sandstone, deposited at the dawn of the Jurassic (about 200 million years ago); in most areas, it sits atop late Triassic redbeds of the Chinle formation.  The Wingate forms massive red cliffs with vertical striations, often giving it a curtain-like appearance.  Atop the Wingate, the Kayenta formation of horizontal siltstones, conglomerates and sandstone separates it from the second major eolian sandstone of the Jurassic, the Navaho Sandstone.  White to pale pink in color, the Navaho has horizontal striations and also forms prominent cliffs; however, it erodes into rounded domes, wavy ledges and curved slickrock formations, many of which are honeycombed and pock-marked by wind-driven sand.  The Carmel Formation, a thin layer of shale and limestone, sits atop the Navaho Sandstone, separating it from the Entrada Sandstone, a salmon-colored eolian sandstone that, like the Navaho, erodes into rounded outcrops.

Exposures of the Wingate and Navaho Sandstones are widespread across the Colorado Plateau; both form cliffs in Canyonlands National Park, in the Escalante River Canyon and on the Vermillion Cliffs, north of Kanab, Utah.  Wingate Sandstone forms the sheer walls of the Colorado National Monument while Navaho Sandstone forms the spectacular cliffs of Zion Canyon, the domes of Capitol Reef National Park and the towering rock walls along western portions of Lake Powell.  Entrada Sandstone also outcrops in Colorado National Monument but is most famous for its many arches and rock formations throughout Arches National Park.  Once desolate dune fields, these magnificent sandstones now invite exploration and their images grace calendars and coffee table books across the globe.

The Desert Hawk

Zone-tailed hawks inhabit the Desert Southwest, from Southern California to southwest Texas, and range southward through Mexico, Central America and semiarid regions of South America; most of those that breed in the U.S. winter in Mexico.

A large but slender buteo, zone-tailed hawks resemble turkey vultures when in flight and often soar with flocks of those scavengers; indeed, some ornithologists believe that this behavior is an effort to deceive their prey (small mammals, birds and reptiles) that tend to ignore the harmless vultures.  Preferring desert and semiarid grasslands with nearby trees and cliffs, zone-tailed hawks are best found near desert ranges where they roost and nest in wooded canyons.  After engaging in spectacular mating flights, characterized by steep dives, these raptors construct a nest of sticks in a tree or on a rock ledge; two or three eggs are generally produced.

Easily identified by their black plumage, yellow legs, banded tail and vulture-like flight, zone-tailed hawks adapt well to dry habitats and their population appears to be increasing in the Desert Southwest.  Most return from Mexico by early spring and generally remain in the U.S. through mid autumn; a small number may be encountered in southern Arizona or New Mexico during the winter months.

The Painted Desert

The entire Colorado Plateau, from Dinosaur National Monument in northwest Colorado to the San Rafael Swell in central Utah and southward to northern Arizona and northwestern New Mexico, might be called a painted desert.  Its colorful strata of late Paleozoic and Mesozoic sediments, sculpted into scenic canyons, buttes and mesas by the Colorado River and its tributaries, reflect the bright sunshine of that semiarid landscape.

Officially, however, the Painted Desert is a swath of northeastern Arizona that runs along the eastern edge of the Little Colorado River Valley, northeast and east of Flagstaff.  Named for its colorful badlands of the Chinle Formation, this scenic terrain arcs for more than 150 miles, from the eastern edge of the Grand Canyon to the vicinity of Petrified Forest National Park, east of Holbrook.  The banded strata of the Painted Desert are composed of siltstones, sandstones and volcanic mudstones (primarily bentonite), deposited in the late Triassic Period (about 210 million years ago) as Pangea began to rift apart; the colors result from hematite and other minerals within the varied layers of sediment.  Since their deposition (and especially during the wet climate of the Pleistocene) the Chinle Formation has eroded into a maze of hills and valleys; in some areas, a resistant cap of sandstone protects the soft, underlying sediments, producing buttes and mesas.

Almost all of the Painted Desert lies within the Navaho Nation and large portions have no road access.  This fascinating and beautiful landscape is best observed in the vicinity of Cameron (on U.S. 89), from Arizona 87, northeast of Winslow, and at Petrified Forest National Park, east of Holbrook.

The Sea of Cortez

During the Miocene Period, some 25 million years ago, rift volcanism began to develop in the region now occupied by extreme southeastern California, southwestern Arizona and northwestern Mexico.  This rifting was triggered primarily by a northern extension of the East Pacific Rise, a mid oceanic ridge that stretches across the southeastern corner of the Pacific Ocean.  Extensive faulting through this rift zone caused blocks of crust to drop below the adjacent terrain and, by 5 million years ago, the sea had invaded from the south. Augmented by the wet climate of the Pleistocene, the Colorado River swept enormous quantities of erosional debris into the northern end of this new sea, producing a vast delta that, today, obscures the connection of the Gulf of California Rift with faults of the Salton Trough and San Andreas network to its northwest.

Having torn the Baja Peninsula from mainland Mexico, this rifting, which continues today, transmitted pressure along the San Andrea Fault and across the landscape of Southern California, lifting fault block mountains and crumpling up the Transverse Ranges north of the Los Angeles Basin.  Knifing into the southern portion of the Sonoran Desert, the Sea of Cortez (or Gulf of California) is lined with rich estuaries and marine wetlands, producing a dramatic contrast with the dry, cactus studded uplands that border its channel.  The northern portion of the Sea, its basin partly filled by submarine layers of the Colorado River Delta, is much shallower and more saline than the central and southern regions. Numerous islands and islets rise above the surface of the Sea while rifting and volcanism persist in its deep channels, gradually widening the Gulf; eventually, the Baja will move off with Southern California, riding atop the Pacific Plate and destined for southwestern Alaska.

Among the most diverse and productive marine ecosystems on Earth, the Sea of Cortez has long been renowned for its rich fisheries, massive sea bird colonies and wide variety of resident and wintering cetaceans.  Yet, despite the cooperative efforts of many regional and international conservation organizations, this young, fragile ecosystem is threatened by human activity; coastal wetland destrution, pollution and overfishing all take their relentless toll.

The Kaibab-Coconino Plateau

As the Paleozoic Era gave way to the Mesozoic, some 225 million years ago (MYA), an ovoid upwarping of Earth's crust developed in what is now northern Arizona.  Reinforced during the Laramide Orogeny (the formation of the Rockies, 70 MYA), this broad ridge was eventually covered by layers of Mesozoic and Tertiary sediments (both erosional and volcanic).  Late in the Tertiary Period, the Miocene-Pliocene Uplift (stretching from about 15-5 MYA) lifted the entire Colorado Plateau and its rim of mountain ranges another 5000 feet, increasing stream erosion across the Province.  Rising on the west side of the Continental Divide, the Colorado River flowed westward and gradually southward to enter the Sea of Cortez; en route, it crossed northern Arizona, entrenched in the younger sediments that covered the Kaibab-Coconino ridge.  As the Colorado Plateau rose beneath it, the river was forced to cut down through this ridge of Paleozoic rock (and the upper layer of the ancient Precambrian basement that lies beneath it).  Augmented by the wet climate of the Pleistocene (2 to 0.01 MYA), the Colorado thereby sculpted the Grand Canyon, the most spectacular chasm on our planet.

The ridge itself, oriented NNW to SSE, has since been uncovered by erosion.  Streams from its eastern edge drain directly into the Colorado (or into the Little Colorado south of the Grand Canyon), while its northwest flank drains to the Colorado via Kaibab Creek and its southwest flank feeds the Cataract River, another tributary of the Colorado.  The exposed ridge is composed primarily of Kaibab limestone overlying Coconino sandstone; that portion north of the Grand Canyon is known as the Kaibab Plateau while its segment south of the Canyon is referred to as the Coconino Plateau.  The rock strata of the plateau, deposited during the Permian Period, form the upper layers of the Grand Canyon

The Kaibab Plateau rises to elevations that exceed 9200 feet, supporting a rich forest of fir, spruce and aspen, giving way to ponderosa pine and then pinon-juniper woodlands at lower elevations.  The Coconino Plateau is 7400 feet above sea level at the south rim of the Grand Canyon and gradually lowers toward the west, south and east; it is covered primarily by ponderosa pine parklands.  South of the Coconino Plateau, the landscape is dominated by the high peaks and scattered cones of the San Francisco Volcanic Field, including Humphreys Peak (12,633 feet), the highest point in Arizona.

Musk Hogs

Collared peccaries, otherwise known as javelinas or by their more colorful title of musk hogs, are native pig-like residents of the Sonoran and Chihuahuan Deserts of the Southwest U.S., from southern Arizona to southwest Texas. They and other peccary species are also found southward through Mexico, Central American and most of South America. All are descendents of a Eurasian ancestor that split from the common pig lineage back in the Eocene, some 50 million years ago.

Living in herds of up to 50 individuals (10-20 is typical), collared peccaries roam the canyons and arroyos of the Desert Southwest, under the control of a dominant male. He breeds with females in the group throughout the year and pregnant females temporarily leave the herd to deliver their young (usually 2) in a den or hollow log. Older sisters help to raise their new siblings and newborn females are sexually mature within a year.

Thinner and longer-legged than common pigs, collared peccaries have a coarse coat of gray-brown hair with a darker mane down their back and a lighter ring around their neck; while their eyesight is rather poor, these desert residents have a keen sense of smell. Short, sharp tusks offer some protection from predators (mountain lions, coyotes, bobcats) but their aggressive nature and group mentality provide their best defence. Omnivorous, peccaries feed on a variety of plant materials (prickly pear cactus and agaves are favored) but also consume eggs, reptiles and carrion; avoiding the heat of mid-day, they usually forage in the early morning and evening hours. The name "musk hog" is derived from the potent musk gland on their upper rump which they use to mark their territory and one another.