The Lassen herd winters in lower elevations in the Secret Valley, Bull Flat, and the Five Springs Wilderness Study Area north of the Skedaddle Mountains and east of Shaffer Mountain, as well as in the Dry Valley Rim Wilderness Study Area. Summer ranges are spread out, with some individuals migrating north to the Madeline Plains and others heading west to Willow Creek Valley, Grasshopper Valley, and Eagle Lake (fig. XXX). An unknown portion of the herd are better characterized as residents. The primary threat to pronghorn in the Lassen herd is the conversion of perennial shrublands to exotic annual grasslands following wildfires. The 2012 Rush Fire burned 271,911 acres in Lassen County within the boundary of the Lassen herd, expanding invasive annual grasslands with altered fire regimes which increase fire frequency and promote the further expansion of exotic grasses. Overabundant free-roaming equids, feral horses and burros, regularly exceed the appropriate management level of the Twin Peaks Herd Management Area, thereby reducing forage and water available for pronghorn. The expansion of juniper into the shrub steppe limits the amount of forage available for pronghorn while increasing the risk of mountain lion predation. The population has been stable to slightly increasing since the 1992-1993 winter die off in northeast California, averaging 974 animals counted during aerial winter surveys (B. Ehler, California Department of Fish and Wildlife, written commun., 2023). CDFW is planning to mark 35 pronghorn with GPS collars in winter 2024 to estimate the population using mark resight surveys. These mapping layers show the location of the migration corridors for pronghorn (Antilocapra americana) in the Lassen population in California. They were developed from 14 migration sequences collected from a sample size of 7 animals comprising GPS locations collected every 1-6 hours.