California Pronghorn Clear Lake Annual Range

The Clear Lake herd contains migrants, but this herd does not migrate between traditional summer and winter seasonal ranges. Instead, much of the herd displays a nomadic tendency, slowly migrating north, east, or south for the summer using various high use areas as they move. Therefore, annual ranges were modeled using year-round data to demarcate high use areas in lieu of modeling specific winter ranges. The areas adjacent to Clear Lake Reservoir were heavily used during winter by many of the collared animals. A few collared individuals persisted west of State Route 139 year-round, seemingly separated from the rest of the herd due to this highway barrier. However, some pronghorn cross this road near Cornell and join this subgroup. Summer ranges are spread out, with many individuals moving southeast through protected forests or over the state border into Oregon. A few outliers in the herd moved long distances south, crossing State Route 139 to Oak Ridge, or east into Likely Tables pronghorn herd areas. Drought, increasing fire frequency, invasive annual grasses, and juniper encroachment negatively affect pronghorn habitat. Recent population surveys indicate a declining population (Trausch and others, 2020). Juniper removal on public and private lands has potential to improve habitat quality and potentially reduce predation (Ewanyk, 2020).
These mapping layers show the location of the annual range for pronghorn (Antilocapra americana) in the Clear Lake population in California. They were developed from 47 migration sequences collected from a sample size of 24 animals comprising GPS locations collected every 1-6 hours.