Toward a Philippine Bat Call Library: Acoustic Characterization of Insectivorous Bats in Bulacan, Luzon Island, Philippines

Abstract

The diversification in call features across different echolocating bat species can provide sufficient information for reliable species identification. In the Philippines, bat bioacoustics is still a growing field. There is a need for a well-developed reference library of calls from different species of insectivorous bats, representing different habitats across each species’ geographic ranges. This study aims to contribute to the building of an echolocation call library for Philippine insectivorous bats. We describe the echolocation calls of 15 species from five families captured in Bulacan province on the island of Luzon. A total of 321 echolocation calls from 105 individuals released in an enclosure were recorded using a Pettersson Elektronik M500 USB ultrasound microphone. Using discriminant function analysis, we assessed the potential of using call parameters in classifying bat echolocation calls to species correctly. Regardless of sample size, correct overall cross-validated classification levels were 92.8% for CF-dominated calls from Hipposideridae and Rhinolophidae families, and 96.9% for FM-dominated calls from Vespertilionidae and Miniopteridae families. When variations in classification levels due to sample size were considered, 98.4% of CF-component dominated calls (four species removed due to small sample size) and 98.9% of FM-component dominated calls (one species removed due to small sample size) were successfully classified into their species. Calls from one species under the Emballonuridae family were characterized. We found some conflicts in identification between species belonging to species complexes, particularly within Hipposideridae. Nevertheless, our results have shown that echolocation calls can be a reliable method in the identification of insectivorous bat species and can complement morphometric and molecular data. The current research contributes to the bat call library we are building as a reference for future taxonomic and ecological studies in the Philippines.