The monument’s biological resources include a spectacular diversity of plant and animal species. Some of the higher peaks include unique woodland assemblages, while much of the lower elevation lands offer one of the most structurally complex examples of palo verde/mixed cacti association in the Sonoran Desert. The dense stands of leguminous trees and cacti are dominated by saguaros, palo-verde trees, ironwood, prickly pear, and cholla. Important natural water holes, known as tinajas, occur in the monument.
The most striking aspect of the plant communities within the monument are the saguaro cactus forests. The saguaro is a signature plant of the Sonoran Desert. Individual saguaro plants are indeed magnificent, but a forest of these plants, together with the wide variety of trees, shrubs and herbaceous plants that make up the forest community, is an impressive site to behold. The saguaro cactus forests within the monument are a national treasure, rivaling those within the Saguaro National Park.
The rich diversity, density, and distribution of plants in the Sand Tank Mountains area of the monument is especially striking and can be attributed to the management regime in place since the area was withdrawn for military purposes in 1941. In particular, while some public access to the area is allowed, no livestock grazing has occurred for nearly fifty years. To extend the extraordinary diversity and overall ecological health of the Sand Tanks Mountains area, land adjacent and with biological resources similar to the area withdrawn for military purposes should be subject to a similar management regime to the fullest extent possible.
Scientific analysis of a pack rat midden from Area A shows that the area received far more precipitation 20,000 years ago, and slowly became more arid. Vegetation for the area changed from juniper-oak-pinion pine woodland to the vegetation found today in the Sonoran Desert, although a few plants from the more mesic period, including the Kofa Mountain barberry, Arizona rosewood, and junipers, remain on higher elevations and north-facing slopes.
The lower, flatter areas of the monument contain the creosote-bursage plant community. This plant community occurs over the open expanses between the mountain ranges, and connects the other plant communities together. Rare patches of desert grassland also occur in the Sand Tank Mountains area. The washes in the area support a much denser vegetation community than the surrounding desert, including mesquite, ironwood, paloverde, desert honeysuckle, chuperosa, and desert willow, as well as a variety of herbaceous plants. This vegetation offers the dense cover bird species need for successful nesting, foraging, and escape, and birds heavily use this plant community during migration.
As we continue to grow our online content we’ll include additional plant life (flora) that can be found in the Sonoran Desert National Monument.
|Organ Pipe Catcus||Night-Blooming Cereus, Peniocereus greggii|
The diverse plant communities present in the monument support a wide variety of wildlife, a robust population of desert bighorn sheep, especially in the Maricopa Mountains area, and other mammalian species such as mule deer, javelina, mountain lion, gray fox, and bobcat. Bat species within the monument include the endangered lesser long nosed bat, the California leaf-nosed bat, and the cave myotis. Over 200 species of birds are found in the monument. Numerous species of raptors and owls inhabit the monument including the elf owl and the western screech owl. The monument also supports a diverse array of reptiles and amphibians, including the Sonoran desert tortoise and the red-backed whiptail. The desert tortoise occupies approximately 25,000 acres of habitat in the Maricopa Mountains.
Most people usually do not think of pronghorn antelope when they think about the animals of the Sonoran desert. Instead images of Gila monsters, rattlesnakes and desert big horn sheep come to mind. This is no accident because all those animals live in healthy populations throughout the Sonoran desert. Unfortunately the same cannot be said for the Sonoran pronghorn.
As we continue to grow our online content we’ll include additional animals (fauna) that can be found in the Sonoran Desert National Monument.
|Long-nosed Leopard Lizard, Gambelia wislizenii|
Surrounding Table Top Mountain, like green ribbons are miles desert washes, known as arroyos in Spanish. These arroyos are the result of countless flash floods that carved the landscape. Bunched along the edges of the arroyos are desert trees and shrubs. Attracted to the seasonal runoff concentrated here these plants grow taller and denser. These areas are known as xeric-riparian communities. The verdant vegetation, with more food, water and cover, attracts wildlife in greater numbers. Arroyos not only offer more food, water and shade from the intense summer heat, they are wildlife corridors where animals can travel in relative safety.
Resources such as food, water and cover are not uniformly dispersed so it is necessary for those who can move do so in search of what they need to survive. Large mammals and birds do move around considerably. Many species of birds are migratory and do travel great distances, and the SDNM’s large mammals, mule deer, javelina and big horn sheep can move considerable distances to find what they need to survive.
Water is the most limited resource in the SDNM. There are no perennial streams within its boundaries. Rainfall is the only natural source of water available to plants and wildlife. Water temporarily flows through the arroyos during the rainy seasons and can be stored in tanks or tinajas or charcos.
Tinajas are basins caved out of bedrock by the erosional power of water. They vary in volume from a few gallons to hundreds of gallons and provide the only freshwater for many miles. Sometimes these tinajas are filled with sand. Thus the origin of the name of the Sand Tanks Mountains, in the SDNM. So important were theses tanks that many geographical locations in southern Arizona derive their names, for example the White Tank Mountains, west of Phoenix, Tinajas Altas Mountains in the southwest corner of Arizona near Yuma.
Charcos are large puddles, earthen tanks, formed in the soil. Commonly known as cow tanks, they are human made and are found in areas where livestock operations are undertaken. Charcos attract native wildlife and are good places to catch a glimpse of a mule deer during the warmer times of the year.
Plants store most of the water found in the SDNM. Desert plants have evolved mechanisms to store and use water efficiently. Desert animals have evolved to use water efficiently through behavioral and physiological means Several species of animals, such as the kangaroo rat get all the water they need from the seeds they eat and much of the year mule deer and bighorn sheep get their water from the plants they eat. All animals avoid the being out during the hottest part of the day by staying in the shade, found in arroyos, or in a burrow underground. Many are nocturnal.
Rainfall in the SDNM ranges from about 3 or 4-inches per year in the drier portions and as high as 7 or 8 – inches in the wetter regions. Rainfall distribution is sporadic in the Sonoran Desert. One area may receive several inches of rain from a brief thunderstorm whereas a desert plain or mountain two miles away will receive none. Plants do not move so they are stuck, but birds, mule deer, bighorn sheep, lions and coyotes to name a few will travel to the areas where it recently rained. Most of the time the rainfall quickly infiltrates into the sediment to be taken in by plants or during the summer evaporates. Coyotes are known to dig into the sand of arroyos for water. Birds and other creatures often take advantage of their resourcefulness.