Effects of passage manipulation on cave climate and bat behavior: Management implications for cave-dwelling bats

Scope and method of study. The intent of this study was to compare abiotic (ambient temperature, substrate temperature, and airflow) and biotic (initiation of exit flights by bats) characteristics in caves that have modified entrances and passages to those with unmodified open-passages in eastern Oklahoma. Variables were recorded at caves during summers 1999 and 2000 and winters 1999--2000 and 2000--2001.; Findings and conclusions. No differences occurred in mean ambient and substrate temperatures inside three gated and three open-passage caves during summers or winters 1999--2001. Differences in ambient and temperature ranges occurred between gated and open-passage caves only in winter 1999--2000 at distances closest to cave entrances. Initiation of flight emergence measured at three gated and three open-passage caves inhabited by colonies of gray bats in summer 1999 and 2000 showed no differences. Statistical differences between long-term summer ambient conditions monitored inside two additional caves before and after management efforts modified their respective cave passages were rare. However, differences in ambient and substrate temperature means during winter were more common. Few differences occurred in ambient or substrate temperatures and relative humidity at any of three distances between natural airflow and intentionally obstructed airflow conditions in caves OK-8 and OK-9. It is apparent from these data that caves with modified entrances and passages, exhibiting what might be considered moderate to low volumes of airflow, show no changes in ambient and substrate temperatures when airflow moves outward in summer and only slight changes in winter. Data also show that internal gate systems do not impede or delay exit flights of colonies of gray bats <30,000 individuals, or result in increased predation.