Oreamnos americanus
mountain goat

The native range of this species is from southeast Alaska to Washington, western Montana, and central Idaho. Mountain goats, Oreamnos americanus, are native to the northern Rocky Mountains. They have also been introduced to parts of South Dakota, Colorado, and Washington. ()

Mountain goats prefer steep, rocky areas with cliffs or bluffs in alpine or sub-alpine regions. They prefer areas with sufficient escape terrain (steep rocky areas), moderate slopes, mid-elevations, and southern exposures. They migrate between lowland winter areas and high elevation summer ranges. ()

Mountain goats are stout-bodied with a thick coat made up of white hairs with some brown intermixed dorsally. The pure black horns are about 200 to 300 mm long, rather thin, and present on both sexes. They do not shed these horns--annual growth rings increase the horn size. In this way, the age of the goat can be determined by counting the number of annual growth rings. The male's horn, however, curves back greater than the females. Mountain goats have relatively large, oval hooves with an almost rubber-like sole that aids them in climbing steep rock. They have black scent glands between their horns. The body size of a male and female are similar until 3 years of age. After 3 years of age males are usually 7.5 to 15 cm taller than females. Male mountain goats usually weigh between 61.4 to 81.8 kg and females 56.8 to 70.5 kg. ()

Mountain goats typically live until their teeth have been worn completely down--on average, 12 to 15 years in the wild and 16 to 20 years in captivity. This age can be determined by the number of annual growth rings on the interior of the horns. Most goats, however, do not survive more than 12 years. The oldest reported male and female were 15.5 and 18 years old, respectively. ()

The degree of sociality of mountain goats varies throughout the year. They tend to form large groups during the winter and concentrate at salt licks in the spring, but they form smaller groups or are solitary in the summer. They are active from sunrise to mid-day and again at dusk. Mountain goats establish dominance hierarchies at a young age, by means of the kids' playing behavior. Males are dominant during the breeding season, but non-breeding season hierarchy is unusual. At this time, adult females are dominant, while adult males are subordinate to females and juveniles.

Mountain goats dig 25 - 50 mm deep "bedding depressions," where they rest during the mid-day and night. They also dust bathe in these depressions, possibly to remove parasites or shedding skin/hair. These beds have caused damage to certain rare and endangered plant populations in areas of Washington where mountain goats have been introduced. ()

Home Range

Home ranges are approximately 23 square km in the summer and much smaller in the winter. Mountain goats typically migrate latitudinally, so absolute distance between summer and winter home ranges is rather small. A study by Poole and Heard noted that some radio-collared goats used winter and summer ranges that were 8 to 13 km apart (coupled with less elevational change). ()

Mountain goats communicate through vocalitizations during the mating season to attract mates. They display a high frequency of intraspecific aggression. Aggressive behaviors include present threat (a broadside orientation with apparent size enhancement by arching their backs), horn threat (aggressive movement and display of the horns), rush threat (a sudden quick movement toward the antagonist), and orientation threat (a lower intensity form of rush threat involving walking). All of these are examples of bluffing aggression, as individuals rarely suffer serious injuries. ()

Although their diet varies throughout the year, it generally consists of grasses, woody plants, mosses, lichens, herbaceous plants, and other vegetation. They get most of their water from their food and year-round snowbanks. Mountain goats also travel many kilometers in the spring to mineral-rich salt licks.

The mountain goat's main predators are cougars (Puma concolor). The cougar is versatile enough to move around on the mountains and it is big enough to hunt and kill an adult mountain goat. Bears (Ursus species) may rarely catch a goat when they are on the ground, but if the goats stay on the mountain, it would be extremely difficult for the bear to catch it. Eagles occasionally swoop down and carry off newborns. Wolves (Canis lupus) have been known to also attack mountain goats. In July and August of 1995, one wolf killed a yearling female. However, soon after that incident a adult female successfully defended her kid from an adult wolf. This aggressive defense is rare--a study in 2006 noted just 5 occasions in which mothers defended their kids. ()

Ectoparasites that have been found on mountain goats are Dermacentor andersoni (a tick), and a chewing louse, Bovicola oreamnidis. Endoparasites that have been known to affect mountain goats are three species of cestodes: Moniezia benedeni, Thysanosoma actinioides, and Taenia hydatigena. Also 11 species of nematodes: Protostrongylus stilesi, Protostrongylus rushi (both were found on the lungs), Ostertagia circumcincta, O. ostertagi, O. trifurcata, Trichostrongylus colubriformis, Trichostrongylus axei, Nematodirus maculosus and N. helvetianus (the latter 2 found in the small intestines). Also tapeworms seem to be an endoparasite that have affected goats in South Dakota. ()

It has been reported that in places of high mountain goat populations, they cause destruction to plant populations native to that region. This has become a big concern at Olympic and Yellowstone National Parks. Mountain goats are not native to those areas, and are considered an exotic species there. Like other exotic species there is concern about mountain goats bringing in new diseases that will infect native organisms from these areas. ()

Mountain goat hunting is very challenging due to the habitat the goats inhabit.

Because the number of mountain goats has been relatively stable, they are not in any danger of extinction. Some areas, like Yellowstone National Park, have allowed hunters to hunt under controlled conditions to reduce the number of mountain goats. Hunting is not allowed in any places where mountain goats are declining in number, like Cascade Mountains of Washington. Goats in this region are being tagged with GPS collars to track their progress, and find out why their numbers are slowly declining. ()