Where their ranges overlap, western yellow bats (Lasiurus xanthinus) often select roost sites in the fronds of native desert fan palms (Washingtonia filifera) as well as in other palm species. Roost occupancy patterns and characteristics of palm trees or palm oases important for roost selection across the Colorado Desert are unknown. We surveyed 41 palm oasis sites throughout the Colorado Desert and found 33 of those locations to have western yellow bat activity, and we confirmed day roosts at 19 sites. Compared to unoccupied palm sites, bats were found roosting in palm oases that were at higher elevations, had evidence of new palm growth, and where palms had a full range of skirt lengths. Our findings have implications for managing palm oases for western yellow bats.