Amphibians may be the last thing people think of when they visit Arches. However, the park is home to a variety of frogs and toads, as well as one species of salamander. Witnessing a chorus of toads may be one of the most memorable experiences canyon country has to offer. It is an awesome event that can fill a canyon with sound, sometimes for hours.
Amphibians are animals that have two life stages: a larval, aquatic form and an adult, terrestrial form. This is the difference between a tadpole and a frog. In Arches, amphibians lay their eggs in the potholes, springs and intermittent streams like Courthouse Wash.
Adult amphibians may wander away from water, but usually remain nearby and wait out dry periods in burrows. Breeding (and toad choruses) usually occurs on spring and summer nights after significant rainfall. Male frogs and toads vocalize. Females lay long strings of gelatin-covered eggs which, depending on the species, may hatch within hours. Metamorphosis can take weeks, though the Great Basin spadefoot toad transforms to adulthood in as little as 14 days, the quickest of any amphibian.
Birds are the most visible animals in Arches. Even on the hottest summer day, turkey vultures, ravens, and white-throated swifts circle above the rock formations. During winter, juncos and white-crowned sparrows forage around trees and shrubs. While Arches may not be considered a bird watching hot spot, 273 species have been seen in the park, including seasonal and year-round residents as well as migrants.
Arches owes much of this diversity to riparian corridors like Courthouse Wash and the Colorado River (which forms the park’s southern boundary). In the desert, animal life tends to concentrate around riparian areas because of the abundance of food, water and shelter. During spring and summer, songs from birds like blue grosbeaks, yellow-breasted chats, spotted towhees, and canyon wrens fill these areas. You might see great blue herons hunting the shallows for fish, while Cooper’s hawks deftly maneuver through the tangle of trees beyond the riverbanks.
Many birds favor the “upland” areas where grasses, shrubs and small trees dominate. Say’s phoebes, black-throated sparrows and western meadowlarks frequent grasslands. Pinyon jays, scrub jays, juniper titmice and black-throated gray warblers are usually seen in pinyon-juniper woodlands.
Since they can fly, it is difficult to generalize about what birds will be found in a particular habitat. However, regardless of habitat or season, the common raven figures prominently in the desert landscape. Ravens are intelligent birds that, according to scientists, display abilities to play and problem-solve that are rare among animals. This jet-black member of the crow family is also very vocal, using a variety of sounds for communication. Perhaps because of these qualities, ravens have achieved a certain stature in both European and Native American folklore.
Arches monitors bird populations at several selected locations in both upland and riparian areas. Some surveys count all birds, while others focus on birds that actually nest in the park, such as peregrine falcons. Findings from these surveys and others like them are used to monitor the health of local bird populations and estimate species richness throughout the country.
Almost 50 species of mammal are known to live in Arches. Some, like desert cottontails, kangaroo rats and mule deer, are common and may be seen by a majority of visitors. However, many desert animals are inactive during daylight hours or are wary of humans, so sightings can be truly special events. Tracks and scat are the most common signs of an animal’s presence.
Arches’ hot climate and lack of water favors small mammals. Because of their size, these animals are less able to migrate, but have an easier time finding shelter and require less food and water to live. Rodents are numerous: there are eleven species of mice and rats alone.
One animal uniquely adapted to life in the desert is the kangaroo rat. This rat lives its entire life consuming nothing but plant matter. Its body produces water by metabolizing the food it eats. However, even the kangaroo rat is prone to spending the hottest daylight hours sleeping in a cool underground burrow and may even plug the opening with dirt or debris for insulation.
Larger mammals, like mule deer and mountain lions, must cover more territory in order to find food and water, and sometimes migrate to nearby mountains during summer. In Utah, around 80% of a mountain lion’s diet consists of mule deer, so these animals are never far apart. However, unlike mule deer, mountain lion sightings are very rare.
Desert bighorn sheep live year-round in Arches, and are frequently sighted along Highway 191 south of the visitor center. These animals roam the talus slopes and side canyons near the Colorado River, foraging on plants and negotiating the steep, rocky terrain with the greatest of ease. Once in danger of becoming extinct, the desert bighorn are now making a tentative comeback that has been fueled by the healthy herds in nearby Canyonlands National Park.
Along with cacti and sand dunes, reptiles have become icons of the desert. The only reptiles found in Arches are snakes and lizards. These underappreciated, sometimes feared, animals play an important role in the high desert ecosystem. Lizards and snakes help control insect and rodent populations. In turn, both are potential meals for birds and mammals.
All reptiles are cold-blooded or, more accurately, “ectothermic,” regulating body temperature via external sources rather than internal metabolism. A reptile’s metabolic rate is very low, but so are its energy needs. Since keeping warm in the desert does not require much work, reptiles are well adapted to this environment. What energy they do generate can be used for reproduction and finding food instead of heating and cooling.
Of course, there are drawbacks to this lifestyle. Since they don’t pant or sweat, reptiles can’t endure extremely high temperatures without shade. Nor can they endure prolonged sub-zero temperatures. When it’s cold, reptiles hibernate or enter into an inactive torpor. Food stored as fat in their tails helps lizards survive these long periods of inactivity, so losing a tail can be life threatening.
If you visit Arches during the summer, you are sure to see lots of lizards. After birds, these reptiles are the most active animals once daytime temperatures reach 90 degrees and higher. They are usually visible sunbathing on rocks or chasing insects with their lightning-quick reflexes. Lizards found here include the northern whiptail, the desert spiny, and the colorful western collared lizard.
Most of the snakes found in Arches are harmless and nocturnal. All will escape from human confrontations given the opportunity. The midget-faded rattlesnake, a small subspecies of the western rattlesnake, has extremely toxic venom. However, full venom injections occur in only one third of all bites. The midget-faded rattlesnake lives in burrows and rock crevices and is mostly active at night.