In 1927 Lawrence M. Huey described a new subspecies of round-tailed ground squirrel (Xerospermophilus tereticaudus apricus) from the southernmost extreme of the species, in the geographically isolated valley ‘Valle de la Trinidad’ in Baja California, Mexico. The valley has been subject to extensive agricultural conversion and severe overgrazing, which had already begun when X. t. apricus was described. Despite the loss of natural habitat, a single remaining population of this isolated subspecies was re-discovered in 2015. Acoustic surveys documented individuals at 195 of 456 points sampled. The population does not appear to be adversely affected and may actually benefit from some disturbance from cattle. The densest populations were found in open communities of large leguminous trees or shrubs, principally mesquite, which may be critical seasonal diet components. Conservation considerations are discussed.