Impacts of Passage Manipulation on Cave Climate: Conservation Implications for Cave-Dwelling Bats

Abstract

Human disturbance has caused declines in populations of many cave-dwelling bats and other cave-obligate organisms. Cave gating has been used to eliminate human disturbance, but few studies have assessed its impact on internal cave climate. We recorded ambient (air) and substrate (rock) temperatures at specified distances within the entrances of 3 gated and 3 open-passage caves in northeastern Oklahoma during summers 1999 and 2000 and winters 1999–2000 and 2000–2001. No differences occurred in ambient and substrate temperatures at any distance or season between gated and open-passage caves. We also monitored long-term (6 weeks) and seasonal (summer and winter) climate variables at specific distances inside 2 caves (OK-13 and OK-220) before and after modifications of their cave passages/entrances. Ambient and substrate temperatures before and after cave manipulation differed in only 1 of 12 observations in summer but in 9 of 12 observations in winter. We also monitored cave climate 7 days immediately before and after passage modification. Differences occurred at all 8 observations and at 4 of 12 observations before and after entrance and passage manipulation at OK-13 and OK-220, respectively. Airflow did not differ when monitored 7 days before and 7 days after instillation of an internal gate system in the passage of cave OK-220. Our data indicate that caves with modified entrances and passages show no changes in ambient and substrate temperatures in summer and only slight changes in winter. Although temperature changes during winter were statistically different, we posit that their biological implications on endemic cave fauna are minimal.