Diversity and threats to cave-dwelling bats in a small island in the southern Philippines

Abstract

More than 2,000 caves have been documented in the Philippines, yet cave research is very limited. This study was conducted to provide benchmark information on the diversity and ecology of cave-dwelling bats from Samal Island, a small island in the southern Philippines. Bats were surveyed from thirty caves of varying physical features and disturbances. Fifteen species of bats were identified in the island; 14 of which are new records for the island, increasing the island distribution of the identified bats in the country. The abundance of cave-dwelling bats varied from low to high density, with some caves estimated to harbor more than 10,000 individuals. Abundance and richness of cave-dwelling bats positively increased with longer cave length, higher ceilings, bigger and multiple entrances, and presence of water. The Bat Cave Vulnerability Index (BCVI) revealed three high priority caves, 12 medium priority caves and 15 low priority caves, indicating the importance of standardized method in assessing cave disturbance. Traces of tourism and hunting were the most common disturbance factors. The results of this study highlight the need for fundamental data on the distribution, diversity, and ecology of cave-dweling bats in the Philippines. Keywords: BCVI, Cave assessment, Cave disturbances, Mindanao, Samal island