"he knew that they would be coming out onto the plain in the new snow to run the antelope in the moonlight"
Pronghorn antelope (Antilocapra americana)
Creative Commons Attribution Share AlikePronghorn antelope (Antilocapra americana) - Credit: Rvannatta

The herd being chased by the wolf pack are not true Antelope, but belong to the family Antilocapra Americana, the only surviving member of the 5 Antilocaprid species which existed when humans entered North America about 13,000 years ago.

The animal is often known colloquially in North America as the Prong Buck, Pronghorn Antelope, or simply Antelope, as it closely resembles the true antelopes of the Old World and fills a similar ecological niche.