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 Species Spotlight

Male and female mule deer [Photo: Tupper Ansel Blake, US Fish and Wildlife Service]
Male and female mule deer [Photo: Tupper Ansel Blake, US Fish and Wildlife Service]

Mule Deer
Odocoileus hemionus

Description: The mule deer is a moderately large deer with large mule-like ears, from which its name is derived. Mule deer are reddish-brown in summer, turning a blue-gray color in winter. The mule deer has a dark forehead and white patches on its throat, belly and inner leg. The rump of the mule deer has patches of white and its tail is short and white, with a black tip. Male mule deer are up to 70 inches (175 cm) long and 42 inches (106 cm) tall. Females can grow to be 58 inches (145 cm) long. Males average 200-225 pounds (91-102 kg) and females average 110-125 pounds (50-57 kg).

Life History: Mule deer can live up to ten years in the wild. Female mule deer, or does, reach sexual maturity at 18 months. Bucks do not engage in reproductive activity until the age of about 3-4 years. Mule deer breed from November through December, in a period known as "the rut." Males engage in battle over females using their antlers as weapons. Mule deer are polygamous; larger, more prominent bucks may guard several does each season. The antlers of the buck are shed after the breeding season between January and April and as soon as antlers are shed, new ones begin to grow. The gestation period is 210 days with fawns being born between June and August. Female mule deer typically give birth to two live young, often twins. Fawns are spotted at birth, weigh approximately 5.5 pounds (2.5 kg), and are weaned at 60-75 days. Mule deer are herbivorous, and in the southwest, feed on lechuguilla, stool, mesquite, juniper, palo verde, aspen, mushrooms, yucca flowers, shrubs, oak, mesquite beans, janusia, cliffrose, sagebrush, coffeeberry and cacti fruit, among others. The main predators of mule deer are coyotes, mountain lions, bobcats and eagles. The average range of a mule deer is 30-50 square miles (78-129 sq km).

Habitat: The mule deer utilizes many habitats within its range including sagebrush-steppe, pinyon-juniper, pine, aspen-fir and mountain meadows. In general, mule deer prefer open, arid habitats with good ground cover for hiding fawns, and plentiful forbs nearby to eat.

Distribution: Odocoileus hemionus is found throughout North America, with various subspecies stretching from northern Mexico to Saskatchewan, Canada, stretching from the Great Plains in the east all the way to the Pacific coast. The mule deer is common throughout the Cold Deserts ecoregion.

Status: The mule deer is an important game species and is hunted for food and trophy. Mule deer populations often go through boom and bust population cycles, so wildlife managers must adjust hunting permits accordingly. In some areas wildlife managers have opted to control predators (such as coyotes and mountain lions) to better manage mule deer populations. Mule deer are highly affected by drought, as loss of vegetation allows greater predation of fawns and contributes to lower nutrition in pregnant does.


Arizona Game and Fish Department, Mule Deer Profile

Texas Parks and Wildlife, Mule Deer Profile

Mammals of Texas, Mule Deer

 Cold Deserts

Cold Deserts Level 3 Ecoregion Map [Figure: Houston Advanced Research Center using USEPA data]
Cold Deserts Level 3 Ecoregion Map [Figure: Houston Advanced Research Center using USEPA data]

The Cold Deserts (or temperate deserts) ecoregion covers most of Nevada, Utah, western Colorado, northern New Mexico and Arizona. This ecoregion encompasses vast areas within the Southwest and can be more easily described when broken down into five ecological subregions: Arizona/New Mexico Plateau, Central Basin and Range, Colorado Plateaus, Northern Basin and Range, and a small part of the Wyoming Basin.

The Cold Deserts ecoregion is typified by low rainfall, hot summers, and cold winters. The topography consists of plains and tablelands (plateaus or mesas), interspersed with high relief mountainous areas. Generally, the soils are dry, calcareous and typically of the Aridisol order. Most of the lower elevation areas of this ecoregion support a sagebrush semidesert ecosystem, and higher elevation vegetation consists of pinyon-juniper woodlands, transitioning to Douglas-fir, subalpine fir and spruce at higher altitudes. Summer and winter temperature ranges are drastic, with more than a fifty degree difference in average summer temperatures (~75 deg F) versus average winter temperatures (~25 deg F). Cold or temperate deserts typically receive only 10 inches (25 cm) of rain each year. However, high elevation areas can receive much more moisture, thus average rainfall ranges from 3-48 inches (8-120 cm) across this ecoregion. Most rainfall occurs during the winter, with the exception of summer thunderstorms in some mountainous areas.

Common wildlife found in this region includes mule deer, pronghorn antelope, sage grouse and magpie. Cheatgrass, salt-cedar and Russian olive are common invasive species.

Common industries are irrigated agriculture, grazing, mining and tourism.

Read more about the Cold Deserts by maximizing the "Ecological Subregions" box below.

 Ecological Subregions Maximize

 Invasive Spotlight

Cheatgrass (Bromus tectorum) [Photo: Leslie J. Mehrhoff, University of Connecticut,]
[Photo: Leslie J. Mehrhoff, University of Connecticut,]

Bromus tectorum

Description: Cheatgrass is a winter annual in the grass family (Poaceae). This plant grows in small multi-branched tufts from 8-24 inches (24-60 cm) tall, with erect stems terminating in a cluster (panicle) of up to eight hair-covered, bristly, spikelets. The panicle is drooping, 2-8 inches (5-20 cm) long, and a pale green to purplish-red color (when mature). The spikelets are each 1-2 inches (2-4 cm) long and contain 4-7 pubescent flowers. The leaf blades are 2-6 inches (4-16 cm) long by 2-4 mm wide and are hairy, yellowish-green in color, and flat. The fruit is a caryopsis, which is a grain-type fruit typical of the grass family.

Life History: Cheatgrass is a winter annual grass, completing its life cycle in one growing season. It reproduces by seed and is mostly self-pollinated, but cross-pollination can occur. Cheatgrass is a prolific seeder and can produce over 70 million seeds per acre, with seeds remaining viable from 2-5 years. Seeds are mainly disbursed by falling on the ground, but can also be carried by wind or water, and attach to animals, people and machinery. Seedling germination rates are very high, and under favorable moisture and temperature conditions, 95 percent of seeds will germinate. Cheatgrass seeds typically germinate in the late fall, and seedlings can grow 0.8-1.6 inches (2-4 cm) by December. Seedlings overwinter in a semi-dormant state and in the spring quickly establish; maturing, flowering, and producing seed by summer. Cheatgrass dies and dries out in June.

Habitat: Cheatgrass can invade a variety of ecosystems at various elevations. Cheatgrass invades shrub-steppe ecosystems as well as coniferous forests and grows at elevations from 2,500 feet to over 13,000 feet (762-3962 m). It can grow in habitats that receive from 6-27 inches (15-67 cm) of precipitation. Cheatgrass prefers deep, loamy or coarse-textured soils, but can grow on a variety of soils and exposures. It does not grow well on extremely wet or alkaline (high pH) soils. Cheatgrass invades disturbed habitats such as abandoned fields, overgrazed rangelands, or areas recently affected by fire.

Distribution: Bromus tectorum is native to Europe, north Africa and southwest Asia. It was initially introduced to the United States in 1898 when it was brought to Washington State for use as cattle forage. Cheatgrass now grows throughout the lower 48 states, predominantly in the shrub-steppe ecosystems of the western United States, where it has replaced native grasses and sagebrush.

Status: Cheatgrass is an aggressive, non-native plant that is estimated to have invaded more than 100 million acres in the sagebrush-steppe ecosystems of the west. Because cheatgrass grows quickly and dries out quickly, creating greater fuel for fires, the historic fire interval of every 60-110 years in invaded sagebrush-steppe ecosystems has altered to every 0-3 years. Although it is used by cattle as forage in the early spring, as it matures the bristly spikelets become unpalatable and can even cause injury to cattle. Cheatgrass is very successful in areas that have been recently disturbed, invading and dominating these areas for many years. It is on noxious weed lists in 46 of the 48 states where it occurs. Cheatgrass is a successful invader because it can tolerate drought, responds well to fire, and has high seed production and germination rates. Controlling cheatgrass is very difficult and management requires a combination of herbicides, burning, mowing, and grazing. Preventing spring seed production is an important management tool for long-term control of this species.


Florida State University, Silent Invaders, Cheatgrass

US Forest Service, Fire Effects Database

US Forest Service, Weed of the Week

Utah State University Cooperative Extension

 Endangered Spotlight

Chiricahua Leopard Frog (Rana chiricahuensis) [Photo: Jim Rorabaugh, US Fish and Wildlife Service]
[Photo: Jim Rorabaugh, US Fish and Wildlife Service]

Chiricahua Leopard Frog
Rana chiricahuensis

Description: The Chiricahua leopard frog is one of about 29 species of leopard frogs in the Ranidae, or "true frog" family and ranges in size from 2.1-5.4 inches (5.3-13.7 cm) long, with an average length of 4.3 inches (10.8 cm). The Chiricahua leopard frog is green to brown in color with many small, dark spots and interrupted dorsolateral folds (two lines of raised glandular skin running along the back). The Chiricahua leopard frog can be distinguished from other closely related leopard frogs because of its stout body, eyes that are high and upturned on the head, small cream colored spots on the back of the thigh, and relatively rough skin on the back and sides. The call of the Chiricahua leopard frog is a distinct, lengthy (1-2 second) snore.

Life History: The Chiricahua leopard frog can live up to 10 years in the wild. The male Chiricahua leopard frog becomes sexually mature at a length of 2.1-2.2 inches (or about one year), and the length and age for female sexual maturity is unknown. Breeding occurs from February-October, with a shorter breeding period at higher altitudes. Frogs that live in waters with constant temperatures such as desert springs may breed year round. Egg masses are deposited mainly in the spring and summer with the egg mass ranging in size from 300-1,500 eggs. Eggs are attached to floating vegetation and hatch after 8-14 days, depending on water temperature. Tadpoles remain in the water and develop into juvenile frogs over a period from 3-9 months; depending on weather conditions (tadpoles are capable of surviving the winter). The Chiricahua leopard frog is active during the day and night, and feeds primarily on beetles, true bugs, flies, and some fish and snails.

Habitat: The Chiricahua leopard frog historically occurred in desert wetland habitats (cienegas), perennial streams, springs, permanent pools in ephemeral streams, and an assortment of man-made waterbodies. However, due to pressure from non-native predators (e.g. American bullfrog, crayfish, and fish species), the Chiricahua leopard frog has been restricted to marginal habitat in small, ephemeral waters, man-made habitats such as stock tanks, and thermal springs devoid of predators. During extreme drought conditions the Chiricahua leopard frog can burrow into muddy cracks to survive. Ideal habitat for the frog is composed of a diverse set of aquatic sites (e.g. ephemeral streams, springs, and stock tanks) all located at one site, devoid of a large amount of predators, thermally stable, and has unimpaired water quality.

Distribution: Rana chiricahuensis occupies two main ranges, consisting of a northern and southern population. The northern population lives in the mountainous regions of west-central New Mexico and along the Mogollon Rim in central and eastern Arizona. The southern population lives in the mountains and valleys south of the Gila River in southeastern Arizona, southwestern New Mexico and Mexico.Rana chiricahuensis is located in Catron, Grant, Hidalgo, Luna, Sierra and Socorro counties in New Mexico and Apache, Cochise, Coconino, Gila, Graham, Greenlee, Navajo, Pima, Santa Cruz, and Yavapai counties in Arizona.

Status: The Chiricahua leopard frog is a state (Arizona and New Mexico) and federally listed threatened species (2002). The species currently has a proposed designation (March 2011) of critical habitat under review. The species has exhibited a range-wide decline, with populations extirpated at up to 85 percent of historical sites. There are three major factors affecting the decline of the Chiricahua leopard frog: habitat loss, disease, and predation by non-native species. The non-native fungal skin disease Chytridiomycosis is caused by the fungus Batrachochytrium dendrobatidis, which disrupts regulatory functions in the frog's skin, and can lead to death. This disease has already caused the extirpation of several populations of Chiricahua leopard frogs. Another major threat to the frog is non-native predators. American bullfrog, crayfish, non-native bass species, and the tiger salamander have aggressively invaded perennial habitats occupied by the leopard frog, feeding on tadpoles, juveniles and adults, and wiping out Chiricahua leopard frog populations. Habitat modification including loss of habitat, reduced water quantity, and degraded water quality are another threat to this species.


Reptiles of Arizona

USFWS, Chiricahua Leopard Frog Recovery Plan

USFWS, Proposed Critical Habitat Listing

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