Natural Setting
The Grand Canyon and its collection of side canyons cut through over a mile of rock, from the heights of 9,200 feet above sea-level on the North Rim down to 1,200 feet above sea level by the time the Colorado River reaches Lake Mead. With such a range in elevation and slope aspect, a multitude of habitats in which wildlife species can thrive have been established. The Mojave Desert influences the western sections of the canyon, Sonoran Desert vegetation covers the eastern sections, and ponderosa and pinyon pine forests grow on both rims. Natural seeps and springs percolating out of the canyon walls are home to 11% of all the plant species found in the Grand Canyon. The Canyon itself can act as a connection between the east and the west by providing corridors of appropriate habitat along its length.The canyon can also be a genetic barrier to some species, like tasseled eared squirrels.
The aspect, or direction a slope faces, also plays a major role in adding diversity to the Grand Canyon. North-facing slopes receive about one-third the normal amount of sunlight, so plants growing there are similar to plants found at higher elevations, or in more northern latitudes. The south-facing slopes receive the full amount of sunlight and are covered in vegetation typical of the Sonoran Desert.
The upper Sonoran Zone includes most of the inner canyon and South Rim at elevations from 3,500 to 7,000 feet. This zone is generally dominated by blackbrush, sagebrush scrub, and pinyon-juniper woodlands.
The dominant plant of the Mojave Desert Scrub community is the Four-winged Saltbush, Creosote bush and important associated plants include Utah agave, Narrowleaf mesquite, Ratany, Catclaw, and various cacti species. Usually dominant at elevations of 3,500 to 4,000 feet.
The South Rim is generally considered in the Upper Sonoran Life Zone and includes species such as gray fox, mule deer, bighorn sheep, rock squirrels, pinyon pine and Utah juniper.
The North Rim lies in the Boreal Zone. This zone includes the Kaibab Plateau at an elevation of over 8,250 to 9,000 feet. Mountain lions, Kaibab squirrels, northern goshawks, ponderosa pine and blue spruce are all species found here.
Seeps and springs emerging from the rims of Grand Canyon National Park are important to the region’s natural heritage for several reasons: they provide critical water and food resources to wildlife and recreational hikers; they are important point sources of biodiversity and bioproductivity in otherwise low productivity desert landscapes; and they are the focus of human activities, regional history, and land and wildlife management.
Tasseled eared squirrels possess tufts or ‘tassels" of hair extending beyond the tips of their ears. The Abert squirrel inhabits the South Rim and is peppered gray with white underparts, a narrow lateral stripe separates these colors. There is a dark chestnut or russet stripe present on the back.
The Kaibab squirrel inhabits the North Rim of the park and is found only on the Kaibab Plateau in northern Arizona. This squirrel has a black belly and white tail. As this is a unique species, it is afforded the special designation of a National Natural Landmark.
