The Klamath Basin mule deer herd contains an estimated 10,775 deer and features a mix of resident and migratory animals. Most winter ranges are adjacent to the California border near Bly and Lost River, California, in areas featuring western juniper, low shrublands, and early shrub-tree habitat. In spring, these mule deer either migrate northwest to regional national forest lands or northeast past South Fork Sprague River. Summer ranges contain ponderosa pine, mixed-conifer, and early shrub-tree habitat along with alfalfa and other agricultural crops. Notably, one mule deer migrated southeast into California near Goose Lake in May 2019 and spent a year near Deadhorse Reservoir before returning to Oregon in November 2020. Out of four mule deer outfitted with GPS collars during a separate capturing event, one migrates from Lake Albert to Lakeview, Oregon along U.S. Route 395 in spring. This stretch of U.S. Route 395 experienced an average annual daily traffic (AADT) value of 1,002 vehicles in 2018. Several other mule deer also cross sections of U.S. Highway 97, an even busier road that had an AADT value of 5,298 vehicles in 2018. From 2010 to 2022, ODOT recorded an average 65.7 mule deer-vehicle collisions per year along a 44.8 mi (72.1 km) section of U.S. Highway 97 north of Klamath Falls. Klamath Basin mule deer numbers are slowly declining, in part due to reduced summer forage quality (Peek and others, 2002). Forest fire suppression beginning in the 1920s increased canopy closure in the summer range, reducing preferred understory vegetation such as Purshia tridentata (antelope bitterbrush) and Ceanothus velutinus (snowbrush ceanothus). Without sufficient high-quality forage during drought years, mule deer become more reliant on agricultural fields near Klamath Falls as a dependable water source. Canopy closure also contributed to the severity of the 2021 Bootleg Fire, the third largest recorded fire in Oregon, which burned 413,765 acres (167,445 ha) north of Sprague River. These mapping layers show the location of the winter ranges for mule deer (Odocoileus hemionus) in the Klamath Basin population in Oregon. They were developed from 44 migration sequences collected from a sample size of 27 animals comprising GPS locations collected every 5−13 hours.