Bison buyers are set to descend on the Black Hills and northern Panhandle this weekend.

Custer State Park holds its annual buffalo auction Saturday, while the Crawford Livestock Market on Sunday hosts the annual buffalo and longhorn sale for Fort Robinson State Park.

The Custer State Park auction features 256 animals including 62 bull calves, 43 two-year-old pregnant heifers, and  3 heifers that aren’t pregnant.

Park Resource Program Manager Gary Brundige says officials decided to sell more animals than initially planned because of the summer’s drought.

The Fort Robinson sale…which is paired with the annual sale of the Tri-State Longhorn Association…has 88 bison, but also 5 burros and between 135 and 140 longhorns going on the block. The bison sale begins Sunday at 11:00, the longhorn sale at noon.

The goal of both annual sales is the same: to thin each respective park’s herds so that the numbers don’t get too big for the land too support. Officials say that’s especially important after a mild winter and dry summer left the grassland parched and at risk for over-grazing.