Community structure and population trends for bats in Big Bend National Park, Texas over the last 18 years

The Chihuahuan Desert region in west Texas is known to support at least 27 species of bats, 22 species have been documented within Big Bend National Park (BBNP) alone. We examined the relative abundance of 5700 bats of 21 species captured during opportunistic sampling at water sources in BBNP. Sampling took place over 258 net nights (4140 net hours) at 41 sites between 1996-2013. We also noted the results of surveys conducted in BBNP by Easterla between 1967-1971, though site locations and effort varied between the two studies. We found three species were more abundant during our study (Nyctinomops femorosaccus, Tadarida brasiliensis, and Mormoops megalophylla), while Antrozous pallidus and Nyctinomops macrotis were less abundant. Considering four semi-regularly sampled sites with over 30% of captures, we found that T. brasiliensis (33.4%) and A. pallidus (19%) were the most commonly captured species over all years of our study followed by N. femorosaccus (12.7%) and Parastrellus hesperus (12.4%), however relative abundance differed across these sites. We examined May captures in all available years and reported capture rates over time for some species including some known to be susceptible to white-nose syndrome (WNS) in the Eastern US. WNS has not been detected in the park nor in Texas, but reporting these numbers are useful for pre-WNS monitoring.