Females with kids and immature animals are generally found in groups but may form larger nursery bands in early to mid-summer. Usually a single kid is born in late May or early June after a gestation period of approximately 180 days. Twinning occurs rarely but is more frequent following mild winters. Kids are precocious and can keep up with adults when only hours old and hardly larger than snowshoe hares. Nannies seek solitude prior to giving birth but soon join other nannies with newborn kids to form nursery flocks.
Kids usually remain with their mothers until the next breeding season.
Mountain goats may live 14 to 15 years, though most live fewer than 12. Many goats show healed wounds and missing teeth, indicating a high incidence of accidents, presumably from falls. Mountain goats are both grazing and browsing animals, depending on the particular habitat and season of the year. They normally summer in high alpine meadows where they graze on grasses, herbs, and low-growing shrubs. Most goats migrate from alpine summer ranges to winter at or below tree line, but some may remain on windswept ridges.