Desert bighorn sheep have long possessed a romantic image that has captivated visitors to the remote and inaccessible reaches of the Arizona Strip. The magnificent curling horns of the rams have inspired men from the ancient Anasazi rock artists, to the early explorers, prospectors and modern day hunters. Bighorn are intimately tied to the rocky crags and steep cliffs found in many areas of the Arizona Strip. Desert bighorn leap from ledge to ledge at great speed and grip slippery surfaces with the shock-absorbing elastic pads on their feet.
Desert bighorn sheep are members of the family Bovidae, in the order Artiodactyla. They are known to scientists as Ovis canadensis subspecies nelsoni. Bighorn are relatively short and blocky in comparison to mule deer. A full-grown bighorn averages from 76 to 100 cm (30 to 39 in) tall at the shoulder and about 152 cm (60 in) long. The males are typically larger than the females. Adult males range in weight from 73 to 91 kg (160 to 200 lb). Adult females, also known as ewes, averages about 48 kg (105 lb).
The great curved horns, which may reach a full curl, attain a length of up to 102 cm (up to 40 in). The horns grow from the base and stop growing during the breeding season, leaving a growth ring that can be counted to determine a rams age (see figure below). The ewes have smaller horns, seldom exceeding 33 cm (13 in).
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The coat is long, full and coarse, something like that of a goat. Coat color ranges from chocolate to gray-brown, and is generally darker in the summer and fall after the spring moult. The animals have exceptionally acute senses of sight, smell, and hearing.
Distribution and Abundance
Desert bighorn sheep were historically present on the Arizona Strip. By the early 1900s desert bighorn were believed to be extirpated from the Virgin and Beaver Dam Mountains and Paria Canyon - Vermilion Cliffs areas. Small remnant populations were still extant in the Grand Wash Cliffs and Kanab Creek. Since the late 1970's, Arizona Game and Fish Department and the BLM have been cooperatively working to re-introduce desert bighorn sheep to the Arizona Strip. As of 1996 there were four separate populations of desert bighorn occupying four distinct habitat areas on the Strip: the Virgin and Beaver Dam Mountains, Grand Wash Cliffs, Kanab Creek, and Paria - Vermilion Cliffs. The four desert bighorn populations were essentially stable in 1996 at a population of approximately 550 animals on BLM administered lands.
Virgin and Beaver Dam Mountains
The Virgin and Beaver Dam Mountains Habitat Area is located entirely within AGFD Game Management Unit (GMU) 13B. The Habitat Area includes over 220 square miles (141,770 acres) of bighorn habitat on BLM lands. The vegetation is primarily Mohave desert shrub community. Dominant species include creosote bush and Joshua tree in the Virgin River Gorge and Beaver Dam Slope. Higher elevations are dominated by blackbrush merging into pinyon-juniper woodlands. Reliable permanent waters include the Virgin River, a number of perennial springs in Hedricks, Frehner, Hancock, and Elbow Canyons, and two wildlife catchments at Figure 4 Canyon and above Hatchet Valley. This habitat area borders a block of suitable bighorn habitat administered by the BLM in Nevada and Utah.
Sixty-two desert bighorn were released into the Virgin and Beaver Dam Mountains from 1979 to 1982 in three locations. Transplants at Buck and Hedricks Springs failed to establish sustainable populations. Key habitat use areas for bighorn sheep include concentration areas along the Virgin River and at reliable waters in the Virgin and Beaver Dam Mountains. More than 86% of the suitable bighorn sheep habitat is unoccupied. Bighorn sheep hunts were initiated in the area in 1989. Nine bighorn rams were legally taken from 1989 through 1996. In 1996, the area supported an estimated population of 120 desert bighorn. The population was stable from 1990 through 1996.
Grand Wash Cliffs
The Grand Wash Cliffs Habitat Area is located within AGFD GMU 13B. The area includes over 175 square miles (113,360 acres) of bighorn habitat on BLM lands. Mohave desert shrub communities are found along the lower Grand Wash Cliffs. Middle and higher elevations are dominated by blackbrush communities merging into pinyon-juniper woodlands. Reliable permanent waters are limited to a few pot holes and developed wildlife and livestock waters. This Habitat Area borders a block of suitable bighorn habitat administered by the Lake Mead National Recreation Area.
Eighty-three bighorn sheep were released into the Grand Wash Cliffs from 1983 to 1996. Key use areas for bighorn include concentration areas around the Squaw Canyon and Olaf Knolls wildlife water catchments, and in the Pigeon and Snap Canyon areas. More than 87% of the suitable bighorn sheep habitat is unoccupied. Four desert bighorn rams were legally taken in the area between 1989 and 1996. In 1996, the Grand Wash Cliffs Habitat Area supported an estimated population of 90 bighorn sheep. The population generally declined from 1993 through 1995.
The Kanab Creek Habitat Area is located within AGFD GMU 12B and 13A. The area includes over 85 square miles (54,495 acres) of bighorn habitat on BLM lands. Kanab Creek flows south from Kanab, Utah, across the Kaibab Indian Reservation, through BLM land, crosses the Kaibab National Forest, and empties into the Colorado River within Grand Canyon National Park. Permanent water flows south from Clearwater Spring for at least five miles. The major side canyons on BLM lands are arid. Important springs in the area include Grama, Willow and Water Canyon. These springs are also impacted by cattle. Suitable bighorn habitat extends well onto adjacent lands administered by the Kaibab National Forest and by Grand Canyon National Park.
Sixty-three bighorn sheep were released at two locations in the Kanab Creek drainage from 1985 through 1996. These transplants were successful in expanding bighorn sheep distribution in the area. Approximately 20% of the suitable bighorn sheep habitat is unoccupied. Bighorn sheep were hunted in the Kanab Creek drainage until the Grand Canyon National Park was expanded in 1975. Nine desert bighorn rams were legally taken in the Habitat Area, north of the new park boundary, from the re-initiation of hunting in 1991 through 1996. In 1996, the Habitat Area supported an estimated population of 200 bighorn sheep on BLM lands.
Paria Canyon - Vermilion Cliffs
The Paria Canyon - Vermilion Cliffs Habitat Area is located within AGFD GMU 12B. The area includes over 105 square miles (62,030 acres) of desert bighorn habitat on public lands in Arizona administered by the BLM. The Paria River flows yearlong through Paria Canyon from the Utah - Arizona state line to Lee's Ferry, where it empties into the Colorado River. The Vermilion Cliffs, a 3,000 foot escarpment forms the southern edge of the Paria Plateau and dominates the landscape. The rough and convoluted terrain provides excellent bighorn habitat. A number of springs and seeps emanate from the base of the cliffs and side canyons. However, the cliffs are more arid than Paria Canyon. All of Paria Canyon and the Vermilion Cliffs were designated wilderness in 1984 and are almost entirely administered by BLM. The Habitat Area borders other suitable bighorn habitat administered by the Glen Canyon National Recreation Area, Grand Canyon National Park, the Navajo Nation, and the Utah BLM.
Fifty-two bighorn sheep were released in the Paria Canyon - Vermilion Cliffs Habitat Area from 1984 through 1985. These transplants were successful in reestablishing bighorn sheep in Paria Canyon and along portions of the Vermilion Cliffs. Approximately 65% of the suitable bighorn habitat is unoccupied, primarily along the western rim of the Vermilion Cliffs. A total of 14 desert bighorn rams were taken in the habitat area from the initiation of hunting in 1991 through 1996. In 1996, the Paria Canyon - Vermilion Cliffs Habitat Area supported an estimated population of 140 bighorn sheep. AGFD surveys indicate populations were stable to slightly declining from 1990 through 1996.
Desert bighorn habitat is typically rough, rocky, and broken by canyons and washes. The low rugged cliffs of the Virgin and Beaver Dam Mountains, the Vermilion Cliffs, and the Grand Wash and Kanab Creek drainages are ideal for bighorn. Much of the western portions of the Arizona Strip lie within the Mohave Desert. The dominant shrubs include Joshua tree, creosote bush, blackbrush, a variety of warm season grasses. The higher elevations are dominated by pinyon-juniper woodlands, though bighorn are not typically found in dense stands.
Certain basic habitat conditions must be present for bighorn to survive. These include food, water, space and escape cover. Water needs of bighorn may be the most difficult habitat requirement to measure. Some studies have suggested that bighorn sheep may be able to get adequate water to survive from succulent plants.
During the hot summer months, wild sheep stay in shaded areas near water as much as possible and are seldom found more than three miles from dependable water sources. When rain or snowfall occurs, bighorn sheep expand their use of suitable habitat and range out from permanent waters. They also commonly drink from ephemeral pools of water found in rock pockets. Bighorn sheep may be found in woodland habitats on canyon rims throughout the year.
The animals have a short mating season, during which the rams clash head-on in a battle for the ewes; for the rest of the year the sheep usually divide into separate male and female herds.
Information on population, production, harvest and general health of the herd is incorporated into annual management recommendations developed by the Arizona Game and Fish Department.