The Sierra Nevada bighorn sheep (Ovis canadensis sierrae) is a subspecies of Bighorn sheep found only in the Sierra Nevada mountains of California. It was listed as a federally endangered subspecies in 2000. In 2016, over 600 Sierra bighorn remained in the wild; however, in 2023, more recent studies indicate that the population has dropped to approximately 300 individuals.
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DiurnalDiurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
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HerbivoreA herbivore is an animal anatomically and physiologically adapted to eating plant material, for example, foliage, for the main component of its die...
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GraminivoreIn zoology, a graminivore (not to be confused with a granivore) is an herbivorous animal that feeds primarily on grass. Graminivory is a form of g...
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ViviparousAmong animals, viviparity is the development of the embryo inside the body of the parent. The term 'viviparity' and its adjective form 'viviparous'...
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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CursorialA cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. chee...
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CongregatoryCongregatory animals tend to gather in large numbers in specific areas as breeding colonies, for feeding, or for resting.
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GrazingGrazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae. In agriculture...
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PrecocialPrecocial species are those in which the young are relatively mature and mobile from the moment of birth or hatching. Precocial species are normall...
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HerdingA herd is a social grouping of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with...
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Dominance hierarchyA dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social gr...
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Altitudinal MigrantAltitudinal migration is a short-distance animal migration from lower altitudes to higher altitudes and back. Altitudinal migrants change their ele...
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starts withSierra Nevada bighorn sheep range in color from white to dark brown, with a white rump and dark tail. There is some seasonal change in coloration due to the shedding of a thicker winter layer. Specialized hooves with adhesive soles provide traction in steep rocky terrain. Female bighorn (ewes) have shorter, narrow horns, while male bighorn (rams) have massive, curving horns. The horns of both rams and ewes are composed of a dense layer of keratin covering a core of bone. The Sierra Nevada bighorn sheep's specialized hooves are not only essential for navigating their rocky habitats but also play a crucial role in their mating rituals, where males engage in horn-clashing contests to establish dominance. Their horns, which grow continuously, add a new layer each year, creating distinct growth rings that can be used to estimate the animal's age.
Sierra Nevada bighorn sheep are found in the Sierra Nevada located along the eastern boundary of California in Tuolumne, Mono, Fresno, Inyo, and Tulare Counties. They inhabit open areas where the land is rocky, sparsely vegetated, and characterized by steep slopes and canyons. Bighorn prefer open ground with high visibility to better detect predators and allow enough time to reach steep, rocky areas (escape terrain). They try to avoid forests and thick brush if possible. Most bighorn live in subalpine and alpine areas during the summer. During winter, some bighorn occupy high-elevation, windswept ridges, while others migrate to lower elevations to avoid deep snow and to find forage.
Sierra Nevada bighorn sheep are social and live in groups. The group size and composition depend on gender and season. Bighorn sheep females (ewes) generally remain with the same herd in which they were born. Males older than two 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 on suitable winter habitat. During this time, males compete for dominance with behaviors like horn clashes.
Sierra Nevada bighorn sheep are ruminant herbivores (graminivores). They are primarily grazers, consuming various grasses, forbs, and woody vegetation depending on season and location. They often visit naturally occurring mineral licks which provide necessary minerals for bone and muscle growth. In the spring and summer, Sierra Nevada bighorn sheep primarily feed on grasses and forbs, while in the fall and winter, they shift their diet to include more woody vegetation.
Sierra Nevada bighorn sheep breed 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 where they can hide from predators.
Centuries of unregulated hunting, disease outbreaks, and mountain lion predation caused a big decline in this subspecies population. Human-induced threats include habitat loss due to development and climate change, hunting, and competition for food with domestic livestock. However, disease played the largest role in the decline of the subspecies with domestic sheep transmitting virulent diseases, in particular pneumonia from Pasteurella, beginning in the 1870s. By the 1970s about 250 animals remained, occupying only two small areas of their former vast range. Translocations by the California Department of Fish and Wildlife (CDFW) helped to reestablish bighorn herds in their historic habitat, but in spite of these efforts, the population hit a low of about 100 total individuals in 1995. On January 3, 2000, Sierra Nevada bighorn sheep were listed as a federally endangered subspecies.
According to the Wikipedia resource, in 2013, the total population size of the Sierra Nevada bighorn sheep was 300 individuals. Presently, this subspecies is not included in the IUCN Red List and its conservation status has not been evaluated.
Social animals are those animals that interact highly with other animals, usually of their own species (conspecifics), to the point of having a rec...