In Carlsbad Cavern, New Mexico, a small maternity colony (∼100 individuals) of fringed myotis (Myotis thysanodes) regularly roosts >200 m below the surface of the ground and >1.5 km from the nearest opening to the cavern. With many passageways in the cavern that are closer to surface openings, we investigated why females selected a remote area to bear and raise young. Using radiotransmitters and light tags, we determined that bats traveled 1.8 or 2.1 km, depending on which of only two openings was used to exit the cavern. Air temperatures in the passageway containing the maternity colony and adjacent rooms were the warmest in the cavern, and air moisture also was greater in those areas. Warm and stable air temperatures, high humidity, low predation risk, and infrequent human disturbances were advantages of the roost site. For this colony of M. thysanodes, such advantages seemed to outweigh energetic costs and other disadvantages of commuting to a remote area of the cavern on a nightly basis.