Happy #nationalbisonday! An estimated 30 to 60 million bison once roamed North America, until overhunting caused the population to fall to around 1,000 in the mid-1880s. Today, there are more than 500,000 bison in North America, most of which are privately owned. On tonight's episode of #drjeff: Rocky Mountain Vet, we head to the Rocky Mountain Arsenal National Wildlife Refuge in Denver with Dr. Baier and Hector to treat some bison in need of veterinary care. Tune in later at 9pm ET. . . . . . #bison #bisonday #americanbison #animalplanet #rockymountainvet #endangered #bovine #animals #northamerica #northamericananimals #denver #rockymountains #wildlife #wildliferefuge #pictureoftheday #photooftheday