A relict on a lava plateau
The Putoran snow sheep (Ovis nivicola borealis) lives in one of the most remote landscapes on Earth: the Putorana Plateau in northern Siberia. This population is separated from its closest relatives in Yakutia by about 1,000 kilometers of forest, a geographic isolation that makes it a distinct subspecies. The sheep's habitat is a expanse of basalt tablelands formed 250 million years ago by one of the largest volcanic events in planetary history, known as the Siberian Traps. This event created a landscape of flat-topped mountains dissected by deep canyons and fjord-like lakes up to 400 meters deep.
Genetically, snow sheep are more closely related to North American species like the Dall sheep and bighorn sheep than to other Eurasian sheep. Their ancestors crossed the Bering Land Bridge from Siberia into Alaska around 750,000 years ago. The Putoran population became isolated on its basalt plateau thousands of years ago, possibly after the last glacial period, and has adapted to conditions at the extreme northern limit of ungulate life. The total population is estimated to be between 1,500 and 6,000 individuals, and they are listed in the Red Book of the Russian Federation.
Engineered for arctic extremes
Survival on the plateau demands extreme adaptations. The subarctic climate features severe winters that last for nine months, with temperatures plunging as low as -60°C (-76°F). The sheep possess a dense, grayish-brown wool coat that provides insulation against the cold. Both males and females have horns, though the rams' are much thicker and more curved. A large adult ram can weigh up to 120 kg (265 lbs).
During the long winter, the sheep remain on the windswept tops of the plateaus. The high winds clear away some snow, exposing the vegetation below. Their diet consists primarily of lichens, mosses, grasses, and shrubs, which they access by digging through the snowpack. They live in small, sex-segregated groups for most of the year, with males forming bachelor herds. Their main predators in this harsh environment are wolves and occasionally wolverines. The sheep's agility on the steep, rocky terrain of the canyons is their primary defense, allowing them to retreat to precarious ledges where predators cannot follow.