The landscape of Arches, for all of its sparseness, provides life's necessities for a variety of animals that have adapted to meet its demands. Sixty-five species of mammals, 190 bird species, 22 reptiles, 9 amphibians, 8 fish, and many insects live here. Most desert mammals hunt in the early morning and evening hours to avoid the intense desert sun. About one-third of the area's mammals are rodents, which include squirrels, packrats, chipmunks and porcupines. Typically, rodents spend the daylight hours in their burrows. Desert cottontails and black-tailed jackrabbits are also more active at dawn and dusk. Mule deer are the most commonly seen large mammal in the park, especially in the Devils Garden area. Fawns and weak adults provide a food base for the park's large predators: coyotes, bobcats and mountain lions.
The two species of cat are very elusive. If you are lucky, you may spot solitary coyotes foraging either day or night. The coyotes' predations help maintain a natural balance among animal populations in the park. Late in the evening, the yips and howls of one coyote are frequently answered by a chorus of others. Resource protection programs within Arches and Canyonlands National Parks have dramatically increased opportunities for visitors to glimpse the magnificent desert bighorn. The Moab Fault Overlook and along Highway 191 near the park entrance are particularly good places to watch for them. During the breeding season (November through January), extremely fortunate observers may see rams engage in head-butting contests to establish their dominance over the herd. Of the lizards, the western whiptail (its tail is more than twice the length of its body) is the most common. The western collared lizard is very striking, with bright green coloring and a distinctive black collar. Arches is home to a variety of poisonous animals, including rattlesnakes, scorpions and black widow spiders. Always watch where you're walking and never put your hand on a surface you cannot see.
The Desert Ecosystem
Deserts form where global weather patterns and geographic land forms create a climate characterized by less than 10 inches of accumulated moisture annually, and where potential evapotranspiration exceeds precipitation. Arches National Park lies at a latitude north of the equator where dry air masses constantly descend toward the surface of the earth. The area is also in the interior of a large continent away from marine moisture and in the rain shadow of the Sierra Nevada Mountains to the west. All of these factors act to produce the arid environment of Arches. Arches receives an average of 9 inches of precipitation a year, most of it from melting winter snows. The elevation of the park (4,000 to 5600 ft.) and the snow create what is called a cold or high desert. Low moisture in the air allows more sunlight to reach the ground, raising daytime temperatures, another distinguishing feature of a desert. The average maximum summer temperature at Arches is 100 F.
As a result of these unusual conditions, the plants found here are a unique blend not found in other deserts of the world. Desert plants must be able to deal with extreme variations in temperature and water availability, as well as intense sunlight. In this high desert environment, temperatures fluctuate greatly, both daily and annually. In summer, highs climb well over 100 degrees F, while winter temperatures often drop below zero. On a hot summer day the temperature may fall 30 to 50 degrees F as night approaches, because of the low humidity and lack of cloud cover. As the sun sets, rock and sand, which do not hold heat well, release almost 90% of their captured solar energy back to the sky. Without clouds to hold the heat in, the air rapidly cools. Surface temperatures in direct sunlight are commonly 25 to 50 degrees F warmer than the air temperature six feet above. Temperatures in the shade may be cooler by 20 or more degrees. Winter snow and violent thunderstorms fall on thin, sandy soils that do not retain much moisture.