Sierra Nevada Bighorn Sheep
Encyclopedia
Sierra Nevada bighorn sheep (Ovis canadensis sierrae) is a subspecies of bighorn sheep
. Early taxonomic schemes included herds from British Columbia
to southern California
in a broader subspecies Ovis canadensis californiana. More recent genetic testing has indicated that O. c. californiana consists of only a small population located in the southern and central Sierra Nevada, hence should be renamed Ovis canadensis sierrae.
in Tuolumne
, Mono
, Fresno
, Inyo
, and Tulare
Counties. Habitat occurs from the eastern base of the range as low as 4790 feet (1,460 m) to peaks above 14100 feet (4,297.7 m). Sierra Nevada bighorn sheep inhabit open areas where the land is rocky, sparsely vegetated, and characterized by steep slopes and canyons. Wehausen provides a detailed description of Sierra Nevada bighorn sheep habitat throughout its range. They prefer open ground to better detect predators and allow enough time to reach steep, rocky terrain (escape habitat). Forests and thick brush are usually avoided if possible.
Most of the sheep live at higher elevations 10000–14000 ft (3,048–4,267.2 m) in subalpine
and alpine areas
during the summer. During winter, these sheep occupy high-elevation, windswept ridges and tend to prefer south-facing slopes where snow melts more readily or migrate to lower elevations (4800 ft (1,463 m)) in sagebrush-steppe areas to avoid deep snow and to find forage.
Sierra Nevada bighorn sheep are gregarious, with group size and composition depending on gender and season. Spatial segregation by gender occurs outside of the mating season. Bighorn sheep ewes generally remain
with the same band in which they were born. Males older than 2 years of age remain apart from females and younger
males for most of the year. During the late fall and winter, the groups come together and concentrate in suitable
winter habitat. Breeding takes place in late fall, generally November and December. Lambing occurs between late April and early July on safe, precipitous, rocky slopes; most lambs in the Sierra Nevada are born in May and
June. Ewes and lambs often occupy steep terrain that provides a diversity of exposures and slopes for escape cover. The lifespan for both Sierra Nevada bighorn sheep males and females has been observed as
8 to 12 years.
Bighorn sheep are primarily diurnal. They are primarily grazers; however, they may browse woody vegetation at times. Plants consumed include various grass
es, browse, and forb
s, depending on season and location. Naturally occurring mineral licks provide necessary minerals for bone and muscle growth.
on January 3, 2000, following emergency listing on April 20, 1999. In 1995, these genetically distinct Bighorn Sheep
hit a population low of about 100 total individuals, distributed across 5 separate areas of the southern and central Sierra Nevada, and had increased to about 125 in 1999. Since then conditions have been particularly favorable for population growth, with the total number of individuals reaching about 250 as of 2002. Significant population declines beginning in the late 1980s were associated with the bighorn sheep avoiding low elevation winter ranges.
The Nevada Department of Wildlife
estimates that there are 1500 California bighorn sheep located in northwestern Nevada as of 2004. However this population appears to be genetically distinct from the Sierra Nevada population, and may be more properly classified as Desert Bighorn Sheep
(O. c. nelsoni).
Bighorn Sheep
The bighorn sheep is a species of sheep in North America named for its large horns. These horns can weigh up to , while the sheep themselves weigh up to . Recent genetic testing indicates that there are three distinct subspecies of Ovis canadensis, one of which is endangered: Ovis canadensis sierrae...
. Early taxonomic schemes included herds from British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
to southern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
in a broader subspecies Ovis canadensis californiana. More recent genetic testing has indicated that O. c. californiana consists of only a small population located in the southern and central Sierra Nevada, hence should be renamed Ovis canadensis sierrae.
Habitat and behaviors
Sierra Nevada bighorn sheep inhabit portions of the Sierra Nevada located along the eastern boundary of CaliforniaEastern California
Eastern California is a term that refers to the eastern region of California, United States. It can refer to either the strip to the east of the crest of the Sierra Nevada, or to the easternmost counties of California.-Culture and history:...
in Tuolumne
Tuolumne County, California
Tuolumne County is a county in the Sierra Nevada of the U.S. state of California. The northern half of Yosemite National Park is located in the eastern part of the county. As of the 2010 census, the population was 55,365, up from 54,501 at the 2000 census...
, Mono
Mono County, California
Mono County is a county located in the east central portion of the U.S. state of California, to the east of the Sierra Nevada between Yosemite National Park and Nevada. As of the 2010 census, the population was 14,202, up from 12,853 at the 2000 census...
, Fresno
Fresno County, California
Fresno County is a county located in the Central Valley of the U.S. state of California, south of Stockton and north of Bakersfield. As of the 2010 census, it is the tenth most populous county in California with a population of 930,450, and the sixth largest in size with an area of . The county...
, Inyo
Inyo County, California
-National protected areas:* Death Valley National Park * Inyo National Forest * Manzanar National Historic Site-Major highways:* U.S. Route 6* U.S. Route 395* State Route 127* State Route 136* State Route 168* State Route 178...
, and Tulare
Tulare County, California
Tulare County is a county located in the Central Valley of the U.S. state of California, south of Fresno. Sequoia National Park is located in the county, as are part of Kings Canyon National Park, in its northeast corner , and part of Mount Whitney, on its eastern border...
Counties. Habitat occurs from the eastern base of the range as low as 4790 feet (1,460 m) to peaks above 14100 feet (4,297.7 m). Sierra Nevada bighorn sheep inhabit open areas where the land is rocky, sparsely vegetated, and characterized by steep slopes and canyons. Wehausen provides a detailed description of Sierra Nevada bighorn sheep habitat throughout its range. They prefer open ground to better detect predators and allow enough time to reach steep, rocky terrain (escape habitat). Forests and thick brush are usually avoided if possible.
Most of the sheep live at higher elevations 10000–14000 ft (3,048–4,267.2 m) in subalpine
Sierra Nevada subalpine zone
The Sierra Nevada subalpine zone refers to a biotic zone below treeline in the Sierra Nevada mountain range of California, United States. This subalpine zone is positioned between the upper montane zone at its lower limit, and tree line at its upper limit.The Sierra Nevada subalpine zone occurs...
and alpine areas
Alpine tundra
Alpine tundra is a natural region that does not contain trees because it is at high altitude. Alpine tundra is distinguished from arctic tundra, because alpine soils are generally better drained than arctic soils...
during the summer. During winter, these sheep occupy high-elevation, windswept ridges and tend to prefer south-facing slopes where snow melts more readily or migrate to lower elevations (4800 ft (1,463 m)) in sagebrush-steppe areas to avoid deep snow and to find forage.
Sierra Nevada bighorn sheep are gregarious, with group size and composition depending on gender and season. Spatial segregation by gender occurs outside of the mating season. Bighorn sheep ewes generally remain
with the same band in which they were born. Males older than 2 years of age remain apart from females and younger
males for most of the year. During the late fall and winter, the groups come together and concentrate in suitable
winter habitat. Breeding takes place in late fall, generally November and December. Lambing occurs between late April and early July on safe, precipitous, rocky slopes; most lambs in the Sierra Nevada are born in May and
June. Ewes and lambs often occupy steep terrain that provides a diversity of exposures and slopes for escape cover. The lifespan for both Sierra Nevada bighorn sheep males and females has been observed as
8 to 12 years.
Bighorn sheep are primarily diurnal. They are primarily grazers; however, they may browse woody vegetation at times. Plants consumed include various grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es, browse, and forb
Forb
A forb is a herbaceous flowering plant that is not a graminoid . The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory.-Etymology:...
s, depending on season and location. Naturally occurring mineral licks provide necessary minerals for bone and muscle growth.
Species recovery
Sierra Nevada bighorn sheep were listed as an endangered speciesEndangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
on January 3, 2000, following emergency listing on April 20, 1999. In 1995, these genetically distinct Bighorn Sheep
Bighorn Sheep
The bighorn sheep is a species of sheep in North America named for its large horns. These horns can weigh up to , while the sheep themselves weigh up to . Recent genetic testing indicates that there are three distinct subspecies of Ovis canadensis, one of which is endangered: Ovis canadensis sierrae...
hit a population low of about 100 total individuals, distributed across 5 separate areas of the southern and central Sierra Nevada, and had increased to about 125 in 1999. Since then conditions have been particularly favorable for population growth, with the total number of individuals reaching about 250 as of 2002. Significant population declines beginning in the late 1980s were associated with the bighorn sheep avoiding low elevation winter ranges.
The Nevada Department of Wildlife
Nevada Department of Wildlife
The Nevada Department of Wildlife is the state agency responsible for the restoration and management of fish and wildlife resources, and the promotion of boating safety on Nevada’s waters. NDOW has responsibility for the wildlife resources and enforcement of the wildlife and boating safety laws on...
estimates that there are 1500 California bighorn sheep located in northwestern Nevada as of 2004. However this population appears to be genetically distinct from the Sierra Nevada population, and may be more properly classified as Desert Bighorn Sheep
Desert Bighorn Sheep
The Desert Bighorn Sheep is a subspecies of Bighorn Sheep that occurs in the desert Southwest regions of the United States and in the northern regions of Mexico. The trinomial of this species commemorates the American naturalist Edward William Nelson...
(O. c. nelsoni).