Oreamnos americanus (Blainville, 1816)
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publication ID |
https://doi.org/ 10.5281/zenodo.6512484 |
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DOI |
https://doi.org/10.5281/zenodo.6636909 |
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persistent identifier |
https://treatment.plazi.org/id/03F50713-992A-FF91-03D9-F877F77BF203 |
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treatment provided by |
Conny |
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scientific name |
Oreamnos americanus |
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Rocky Mountain Goat
Oreamnos americanus View in CoL
French: Chévre des Rocheuses / German: Schneeziege / Spanish: Cabra blanca de las Rocosas
Other common names: Mountain Goat, Snow Goat, White Goat
Taxonomy. Antilope (Rupicapra) americana de Blainville, 1816 ,
America (probably near Mt. Adams, Washington).
Phylogenetic relationships of Oreamnos to other genera in the tribe Caprini are unclear. Monotypic.
Distribution. W Canada (Yukon, Northwest Territories, British Columbia & Alberta), W USA (SE Alaska, Washington, W Montana & Idaho); its native occurrence in Oregon has not been definitely established. Introduced into several other US states: Alaska (Kodiak, Chichagof, Baranof Is), Washington (Olympic Peninsula), Oregon, C & S Montana, Wyoming, South Dakota (Black Hills), Colorado, Utah, and Nevada. View Figure
Descriptive notes. Head-body 155-180 cm (males) and 140-170 cm (females), tail 10-20 cm, shoulder height 90-110 cm; weight 95-115 kg (males) and 60-75 kg (females). Horn length 21-30 cm (males), horn basal girth 11-16 cm (males). Female horn lengths can equal those of males, but male horns have greater basal girth. Majority of horn growth is completed by the age of three. Males and females have a shaggy, uniformly white, long winter pelage and a prominent mid-dorsal mane. Adult males and females have beards. Males are 40-60% larger than females. Nonetheless, differentiating males from females in the wild is difficult. Females attain peak mass at age six, but males continue to gain mass with age. Maximum longevity in the wild is 15 years for males and 18 years for females, but few goats survive more than twelve years. Diploid chromosome numberis 42.
Habitat. Usually occur in rugged, precipitous terrain under extreme climate conditions from near sea level in coastal areas to above 2700 m. Habitats consist of a mosaic of forage-rich alpine meadows, timbered areas, high-mountain ridges, scree, and barren cliffs that provide escape terrain, especially for females with young. During winter, they use areas within 300-500 m of escape terrain. Nursery groups in summer use habitats from the tree line to higher vegetation, and in winter are found near the tree line and slightly below it on snow-free south and west-facing slopes. Male groups and solitary males can remain in forested areas near the tree line throughout the year. Some populations do not make altitudinal movements. Specific habitat use varies regionally. In the Cascade Range, Washington, Rocky Mountain Goats occur principally at 600-2400 m. In the Caw Ridge area of western Alberta, Canada, they occur at 1700-2180 m in rolling hills with limited rocky, precipitous terrain. Following the rut, females use more rugged, steeper terrain than males and stay closer to escape terrain. Rocky Mountain Goats can move across inhospitable habitat to an unoccupied area of suitable habitat by temporarily using small, isolated patches of landscape. Predation is probably the most significant mortality factor. Major predators include Pumas (Puma concolor ), Gray Wolves (Canis lupus), Brown Bears ( Ursus arctos), and occasionally Coyotes (C. latrans), Black Bears (U. americanus ), Wolverines (Gulo gulo), and golden eagles (Aquila chrysaetos).
Food and Feeding. Mainly graminivorous. Based on food habits throughout their range, summer diet consists of 52% grasses, 30% forbs, and 16% browse. Winter diet is 60% grasses, 8% forbs, and 32% browse. However, diets vary regionally. In Colorado, captive mountain goats ate 88% forbs in summer and 59% in winter, and 11% grasses in summer and 27% in winter. Mosses and lichens comprised 60% of the diet in winter in South Dakota. Bunchgrasses comprised 90% of the diet in Colorado; in another area, annual diet was 60-68% grasses, 25-29% forbs, and 7% browse. In general, grasses or forbs dominate diets in spring and summer and browse, including conifers, dominates in winter.
Breeding. Mating peaks in November-December, and births occur in May-June after a gestation period of 185-195 days. Dominant males probably guard an individual female from other males when the female is in estrus. Prior to parturition, females separate from female groups to give birth. The newborn remains hidden for about a week after birth, until it is strong enough to follow the mother in rugged terrain. Nannies with kids form nursery groups. Nursery groups can exceed 100 individuals, but rarely exceed 30 animals by late autumn and winter. Most births are singletons, and twinning is rare, although triplets have been documented. Females in the established population in Caw Ridge, Canada,first give birth at four or five years of age. They attain mass at a slower pace than other ungulates, reaching peak kid production at eight to twelve years; most yearlings are the offspring of females eight to twelve years of age. On average at Caw Ridge, 87% of kids survived to weaning age and 64% survived to one year of age. Kid survival ranged from 38% to 92%. Survival to two years was 73-5% for yearling males and 84-7% for yearling females. After the age of eight, adult females experienced higher survival rates than males. Over 50% of yearling females and less than 10% of yearling males survived to ten years. Survival of females two to seven years of age was 94%.
Activity patterns. In summer, mountain goats are most active during the cooler periods of early morning and late afternoon but also have activity periods during the night. They usually have six to seven feeding-resting cycles throughout the day.
Movements, Home range and Social organization. Male and female groups are spatially segregated except during the mating season. Only during the rut are adult males dominant over adult females. At other times of the year, adult females are dominant over all age and sex classes. Adult females are highly aggressive and form linear hierarchies. Males can be solitary or form bachelor groups. Horn size, body mass, and body size are not related to social status; age is the most important factor. Males have larger home ranges than females during the rut but smaller home ranges during summer. Nursery groups (females with kids and 1-2year-olds) make longer daily movements than bachelor groups or solitary males. Male home ranges encompass 6-3-21-5 km? and those of females are 8-9-25 km®. Differences in home ranges are probably due to topography and proximity to neighboring groups during the rut. In east-central British Columbia, some mountain goats used separate winter and summer ranges 8-13 km apart; most exhibited seasonal shifts in elevation. In winter, they often used southerly aspects at lower elevations in commercial forest stands. Mountain goats use declined in areas farther than 500 m from escape terrain. The goats were found at lower elevations from evening to dawn more often than they were during the day. They used high-elevation licks that were within their home range or 6-14 km from their typical home range. In coastal Alaska, where goats selected elevations at 300-1200 m, females moved 0-9-5-5 km along valleys during the winter; males moved 1-4-4-3 km. Annual movements of females ranged from 2 km to 6 km and those of males varied from 3 km to 10 km. Mean winter home range size was 1-4 km? for females and 2-7 km? for males and included burned timbered areas. Forty-two percent of male goat use was in mature or old forest (greater than 80 years old) compared to 29% for females. Males and females made less use of young forest (less than 40 years old) and used slopes between 41° and 60° and up to 70° for females.
Status and Conservation. Classified as Least Concern on The IUCN Red List. An estimated 75,000 -110,000 occur in North America, 36,000 -63,000 in British Columbia, Canada, and 24,000 -30,000 in Alaska. Mountain goats occurring outside protected areas are vulnerable to human disturbance because of unregulated tourist activities and habitat destruction resulting from mineral and oil and gas exploration and extraction and clear-cutting forestry practices. Habitat fragmentation is also a concern due to road construction and other developments. Introduction of mountain goats into areas not historically occupied should be done with caution, because they can cause degradation to alpine environments. Mountain goat populations are particularly sensitive to indiscriminate age and gender hunting, so a conservative management strategy is required.
Bibliography. Bailey & Klein (1997), Brandborg (1955), Coté & Festa-Bianchet (2003), Cowan & McCrory (1970), Festa-Bianchet (2008), Festa-Bianchet & Coté (2008), Geist (1964, 1971), Groves & Grubb (2011), Grubb (2005), Hall (1981), Laundré (1994), Lemke (2004), Peek (2000), Pettorelli et al. (2007), Poole & Heard (2003), Rice (2008), Rideout (1978), Rideout & Hoffmann (1975), Shackleton et al. (1997), Taylor, Wall & Kulis (2006), Verts & Carraway (1998), Voyer et al. (2003), White (2006).
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