Because this species likely uses small caves that see little recreational use and rock crevices that are typically in remote settings internal disturbances should be minimal. When such disturbances do occur abandonement of the roost, at least during the time of the disturbance, might be expected. However, certain populations are tolerant of some disturbance as shown by individuals night roosting in the tunnels at Colorado National Monument (Adams 1993). Surface disturbances could affect M. yumanensis when using rock crevices through leaching of toxicants, impoundment of water, and recreational activities such as climbing. Very little work has been done to document such effects on bats and roosting data available for this species in CO is minimal.