Bats occupy a great variety of roost sites during their diurnal refuge, for reproduction and breading activities, like hollow trees, leafs, rocks, buildings and caves. The 45 % of Mexican bat species (60 spp) use caves roosts like obligated or alternative cave-dwelling species. The San Francisco Cave in the municipality of La Trinitaria in the state of Chiapas, is considered one of the most important bat refuge in Mexico but there have not existed complete and actualized information about the bat fauna of this cave. We conducted a bat survey from January to October, 2005, in order to identify the bat species richness, relative abundance of each species and the temporal changes on diversity and utilization patterns of the cave. Bats were captured with mist nets at the cave entry during two nights in each month. Captured animals were identified and marked with temporal marks, and were released after taking standard body measurements, age class and reproductive data.

Results/Conclusions

We captured 1035 individuals of 16 accumulated species from four bat families (Chiroptera: Mormoopidae, Phyllostomidae, Vespertilionidae, Molossidae). Richness varied among sampling months recording lower species number in February (7 spp) and higher richness in April (10 spp). Seven species (Pteronotus parnellii, Artibeus jamaicensis, A. intermedius, A. lituratus, Glossophaga comissarissi, Desmodus rotundus, Tadarida brasiliensis) are considered resident in the cave due to their stable presence in all the sampling months; this species have all their life cycle in this cave. The other species use the cave temporally like alternative diurnal roost or like reproduction site. Relative abundance was fluctuating, and we encountered breeding (pregnant or lactating) females in case of 12 species, which use the cave like a secure roosts in their breeding season. Our results affirm the high importance of this cave for bat conservation: 1) it is the most bat-diverse Mexican cave known at the time, basing on both richness and abundance; 2) in this cave roosts the unique known big colony of the migrating Mexican free-tailed bat (Tadarida brasiliensis) in South-Mexico with an apparently resident population; 3) Is a breeding refuge of almost 12 bat species. Also taking account the actual perturbation and contamination of the cave by the human activities is urgent to find out viable managing alternatives for the conservation of the San Francisco Cave.