We describe dung pellets identified as bighorn sheep (Ovis canadensis; Bovidae, Caprinae) radiocarbon dated to ∼12,500 cal BP, late Pleistocene. Pellets were excavated from a layer of trampled and butchered bison bones in Eagle Cave located in a box canyon tributary of the entrenched Rio Grande, southwestern Texas. Wild sheep are not known historically or from the Pleistocene from this region of the Lower Pecos Canyonlands. Phytolith analysis of the fossil dung revealed that the Ovis diet was predominantly a mixture of cool and warm season grasses, but dominated by warm season grasses. Morphology and content analysis imply that the dung represent a late-summer, or more likely, winter season accumulation.