Because of their importance in the maintenance of ecological processes and sensitivity to multiple stressors, bat activity is increasingly being used to study habitat associations, including the effects of urbanization and other land use changes. However, to be effectively used as a bioindicator, baseline information on bat activity patterns must first be established. In this study, we aimed to determine patterns of insectivorous bat activity, richness, and assemblage within an urban green space in the Philippines’ capital region in relation to habitat type, insect abundance, and environmental conditions, with particular focus on activity at dusk emergence. Bat activity was measured as the number of bat passes per minute using a portable bat recorder at five time intervals from 5:30 PM to 7:30 PM, and compared between 10 open and 10 forested sites. Bat calls were classified into sonotypes based on five call variables. There was no difference in bat activity between forested and open sites, but more sonotypes were recorded in open sites. Both bat activity and sonotype richness peaked between 6:00 PM and 6:30 PM, representing a short foraging bout upon dusk emergence. However, we did not observe significant relationships between bat activity and insect abundance, air temperature, and relative humidity. Our study found considerable bat activity and diversity in an urban ecosystem, a poorly explored field of research in the Philippines. Additional studies are necessary to understand the impact of land use changes on Philippine bats , and to inform their conservation and management in anthropogenically altered habitats.

An inventory of the non-avian terrestrial vertebrate species found within the 493-hectare land area of the UP Diliman campus is presented. Visual encounter surveys for amphibians and reptiles, as well as mist-netting and trapping for mammals, were conducted last August 2019 to early February 2020 on selected study grids on campus. To determine habitat associations, the species richness of each vertebrate class (i.e., amphibia, reptilia, and mammalia) was analyzed with habitat characteristics of the grid using regression analysis. Based on the surveys and recent records (2015 onwards) in literature, a total of 33 species were recorded: seven amphibians, 15 reptiles, and 11 mammals. Comparison with historical records from 1998 revealed that an additional two amphibian species, seven reptile species, and six mammalian species have been sighted within the area since 2015. However, a fork-tongued frog, falling under the genus Fejervarya, and four reptilian species that had previously been recorded within the study sites were not observed. Habitat association analysis revealed that building area is correlated with species richness, with reptilian species richness being positively correlated with it. Overall, this study shows that the UP Diliman campus supports considerable urban biodiversity despite recent developments.

We assessed eight acoustic indices as proxies for bird species richness in the National Science Complex (NSC), University of the Philippines Diliman. The acoustic indices were the normalized Acoustic Complexity Index (nACI), Acoustic Diversity Index (ADI), inverse Acoustic Evenness Index (1-AEI), Bioacoustic Index (BI), Acoustic Entropy Index (H), Temporal Entropy Index (Ht), Spectral Entropy Index (Hf), and Acoustic Richness Index (AR). Low-cost, automated sound recorders using a Raspberry Pi were placed in three sites at the NSC to continuously collect 5-min sound samples from July 2020 to January 2022. We selected 840 5-min sound samples, equivalent to 70 hours, through stratified sampling and pre-processed them before conducting acoustic index analysis on the raw and pre-processed data. Wemeasured Spearman’s correlation between each acoustic index and bird species richness obtained from manual spectrogram scanning and listening to recordings. We compared the correlation coefficients between the raw and pre-processed.wav files to assess the robustness of the indices using Fisher’s z-transformation. Additionally, we used GLMMs to determine how acoustic indices predict bird species richness based on season and time of day. The Spearman’s rank correlation and GLMM analysis showed significant, weak negative correlations between the nACI, 1-AEI, Ht, and AR with bird species richness. The weak correlations suggest that the performance of acoustic indices are dependent on various factors, such as the local noise conditions, bird species composition, season, and time of day. Thus, ground-truthing of the acoustic indices should be done before applying them in studies. Among the eight indices, the nACI was the best-performing index, performing consistently across sites and independently of season and time of day. We highlight the importance of pre-processing sound data from urban settings and other noisy environments before acoustic index analysis, as this strengthens the correlation between index values and bird species richness.