One way in which caves retain low temperatures is through a constant input of cold air from outside the cave. Typically, the caves supporting the largest populations have multiple entrances that allow cool air from outside the cave to come in, creating a circulation of fresh, cooled air. Gates that are meant to keep vandals out of caves have altered the temperature and airflow of hibernacula, resulting in population declines of Indiana bats at many major hibernacula throughout their range. Removing or modifying gates at some of these have given these populations a chance to rebound. Also, the bats seem to prefer a relative humidity of 74 to 100%, although the air is not commonly saturated. Relative humidities of only 50.4% have also been recorded.