The question of whether sheep are native to North America has two distinct answers depending on the type of animal being considered. The continent is home to species of wild sheep that have lived here for millennia, representing a truly native lineage. However, the familiar, wool-producing livestock most people associate with the word “sheep” are not native. These two separate groups arrived on the continent at vastly different points in history, leading to the current distinction between wild and domestic populations. This difference is biological, influencing their physical characteristics, behavior, and ecological roles.
North America’s Indigenous Wild Sheep
North America is home to two primary species of wild sheep: the Bighorn Sheep (Ovis canadensis) and the Dall Sheep (Ovis dalli). These animals are truly indigenous, as their ancestors migrated from Asia across the Bering Land Bridge approximately 750,000 years ago during the Pleistocene epoch. This ancient migration established a presence that predates human arrival on the continent.
The Bighorn Sheep, named for the massive, tightly curled horns of the males, spread throughout western North America, ranging from southwestern Canada down to Mexico. They are specialized inhabitants of rugged, mountainous terrain, using rocky cliffs and steep slopes to evade predators.
The Dall Sheep, often recognizable by their striking white coats, inhabit the colder, high-altitude regions of Alaska and northwestern Canada. These wild species are hardy and self-sufficient, relying on natural instincts and physical adaptations to survive in extreme environments. The Bighorn and Dall sheep represent the wild, native branch of the Ovis genus in North America.
The Arrival of Domestic Sheep
In contrast to the wild species, the domestic sheep (Ovis aries) is an introduced species, having originated in the Old World. Domestication began in ancient Mesopotamia and Central Asia, estimated between 9,000 and 11,000 years ago. These animals were selectively bred over millennia for traits useful to humans, such as high wool production and docility, making them genetically distinct from their wild ancestors.
The introduction of domestic sheep to the Americas began with the arrival of European explorers and colonists in the late 15th century. The first documented transatlantic shipment occurred during Christopher Columbus’s second voyage in 1493, bringing sheep to the Caribbean. Subsequent shipments landed sheep in Mexico, and their flocks spread northward with Spanish settlers into what is now the Southwest United States.
English colonists later introduced their own breeds to the East Coast, with permanent flocks established in places like Virginia by the early 1600s. These animals were primarily livestock, serving as a source of wool, meat, and milk for the growing colonial populations. They are entirely reliant on human management and agriculture for their survival and health.
Distinguishing Wild and Domestic Sheep
The differences between North America’s native wild sheep and the introduced domestic sheep are evident in their morphology, coat structure, and behavior. Wild sheep, such as the Bighorn and Dall, possess a coat composed of stiff outer hair and a fine wool undercoat, which naturally sheds each year. This hair-and-wool combination is essential for thermoregulation in their harsh, mountain habitats and means they do not require shearing.
Domestic sheep, however, have been selectively bred to retain a thick, crimped fleece that grows continuously, making them dependent on humans for shearing. The horns also differ significantly; wild rams have impressive, massive horns used for dominance rituals and defense. In contrast, many domestic breeds are intentionally bred to be “polled,” or hornless, or have much smaller horns.
Ecologically and behaviorally, the two groups are worlds apart. Wild sheep are agile, muscular animals adapted for climbing and surviving in predator-rich environments. Conversely, domestic sheep exhibit a heightened gregarious instinct and a diminished natural defense response due to their long history of domestication. Their reliance on human intervention for health and protection highlights the profound genetic and behavioral divergence from their native North American counterparts.