Bioacoustic Study of Insectivorous Bats

The microbat has developed advanced echolocating ability compared to the megabats or old-world fruit bats that relies mainly on vision and olfaction for food hunting. The microbats orient and capture their prey by means of echolocation that involves ultrasonic calls >20kHz, in which a frequency beyond the range of human hearing. Their morphological features and echolocation calls are designed in correlate with their adaptability with the environment especially with their superiority maneuver, detection and localize targeted object in cluttered environment. In Borneo, there are a total of 100 bats’ species with 85 species from Sarawak (15 Megabats and 70 echolocating microbats). The use of ultrasonic detectors in monitoring echolocation calls by using bat detectors has surged the researchers’ interest to study on bats and their habitat relationship as well as addressing questions concerning their activity patterns despite the limitations in this method. Present study intends to build a call library comprising of different species call frequencies as well as bat activity patterns in Kubah National Park via acoustic measures. To date, higher elevations recorded the highest activity that is determined by the number of passes but lower by species richness as compared to the lower elevation. Acoustic monitoring provides additional data of bat species that occur at each elevation that were not caught during trapping. These data will be highly useful in studying effect of landscape changes in the future

A machine learning framework to classify Southeast Asian echolocating bats

Bats comprise a quarter of all mammal species, provide key ecosystem services and serve as effective bioindicators. Automated methods for classifying echolocation calls of free-flying bats are useful for monitoring but are not widely used in the tropics. This is particularly problematic in Southeast Asia, which supports more than 388 bat species. Here, sparse reference call databases and significant overlap among species call characteristics makes the development of automated processing methods complex. To address this, we outline a semi-automated framework for classifying bat calls in Southeast Asia and demonstrate how this can reliably speed up manual data processing. We implemented the framework to develop a classifier for the bats of Borneo and tested this at a landscape in Sabah. Borneo has a relatively well-described bat fauna, including reference calls for 52% of all 81 known echolocating species on the island. We applied machine learning to classify calls into one of four call types that serve as indicators of dominant ecological ensembles: frequency-modulated (FM; forest-specialists), constant frequency (CF; forest-specialists and edge/gap foragers), quasi-constant frequency (QCF; edge/gap foragers), and frequency-modulated quasi constant frequency (FMqCF; edge/gap and open-space foragers) calls. Where possible, we further identified calls to species/sonotype. Each classification is provided with a confidence value and a recommended threshold for manual verification. Of the 245,991 calls recorded in our test landscape, 85% were correctly identified to call type and only 10% needed manual verification for three of the call types. The classifier was most successful at classifying CF calls, reducing the volume of calls to be manually verified by over 95% for three common species. The most difficult bats to classify were those with FMqCF calls, with only a 52% reduction in files. Our framework allows users to rapidly filter acoustic files for common species and isolate files of interest, cutting the total volume of data to be processed by 86%. This provides an alternative method where species-specific classifiers are not yet feasible and enables researchers to expand non-invasive monitoring of bat species. Notably, this approach incorporates aerial insectivorous ensembles that are regularly absent from field datasets despite being important components of the bat community, thus improving our capacity to monitor bats remotely in tropical landscapes

BATS

A hundred species of bats, representing nine families, are now known from Borneo. Classifi ed as either frugivorous, nectarivorous or insectivorous feeder, their diets permit them to play important roles in the maintenance of ecosystem functions and dynamics, through their action as seed dispersers, pollinators and regulators of insect populations. Of these, the insectivorous bats of the families Hipposideridae, Rhinolophidae and Vespertilionidae contribute the most to species numbers

Survey on the small mammals in Sg. Kangkawat research station Imbak canyon conservation areas

Sg. Kangkawat Research Station is a newly established research station in the Imbak Canyon Conservation Area, Sabah which encompasses both primary and secondary forest areas. Limited data is available on the small mammal diversity for this particular area. Therefore, a survey-based study on small mammal diversity was carried out between the 29th September – 8th October 2018 along the established trails within the vicinity areas of this research station. Small mammal trapping was done using traps (mist nets, harp traps, cage traps and pitfall traps) employed randomly along the Nepenthes trail, the Kawang trail, the South Rim trail and the Pelajau trail. This study documented a total of 32 small mammal species i.e. represented by 26 species (15 spp. of new records for ICCA ) of volant small mammals (Chiroptera) and 6 species of non-volant small mammals (Rodentia, Scadentia, Insectivora, Carnivora). The total number of specimens recorded was 108. A new distribution record on the Free-tailed Bat, Chaerephon cf. johorensis, was documented for Sabah and Borneo during this study

Acoustic Survey on Insectivorous Bats Activity Pattern at Contrasting Elevation in Kubah National Park, Sarawak

Bat monitoring mostly done by using mist nets and harp traps but species that fly high still to be missed out. Additional methods such as acoustic sampling would be able to monitor echolocating bats the tend to avoid the nets. Acoustic sampling gives a better perspective for bat activity monitoring including study their habitat use. Bats activity may vary spatially and temporally. In an area with elevational gradient, it is possible to study the activity of bats simultaneously at different elevation by acoustic monitoring. But first, bat echolocation call libraries are needed as a reference to identify the calls of free-flying species. Therefore, the objectives of this study are to build echolocation call library of Kubah National Park for the purpose of species identification of insectivorous bats through echolocation call; compare the activity pattern of insectivorous bats at contrasting elevation by acoustic monitoring; and identify the other factors affecting activity of bats at contrasting elevation in Kubah National Park. Between November 2018 and February 2019, insectivorous bats were trapped at lower elevation (100-250m a.s.l.) and higher elevation (700-800m a.s.l.) in Kubah National Park and echolocation calls were recorded from a total of 68 individuals, representing 13 species from 4 families. The discriminant function analysis indicated that constant frequency (CF) bats comprised of Families Hipposideridae and Rhinolophidae could be easily distinguished from their calls recorded in the detectors. Acoustic survey on their activity was conducted from November 2018 to August 2019 at lower elevation covered with mixed dipterocarp forests, and at higher elevation covered with Kerangas forests, scrub forests and lower-montane forest. The activity of insectivorous bats at higher elevation is higher compared to lower elevation with 69% of the total bat passes counted from both elevations. In addition, more species were recorded at higher elevation compared to lower elevation. The result was related with iv insect biomass at each elevation but not significantly affected by temperature and moon phase. This study showed that elevational gradient does affect the activity of bats, considering the availability of their food abundance and the habitat use. Overall, acoustic monitoring does provide better way to document species occurrence and ecology information of insectivorous bats. Further investigations on species-specific in response to elevations and climate variables are needed and may increase the power of understanding on factors that influence the bat activity

First recorded sighting of the Critically Endangered Tricolour Langur, Presbytis chrysomelas cruciger (Thomas, 1892) (Primates, Cercopithecidae), in Jemoreng Protected Forest, Sarawak, Malaysia

Presbytis chrysomelas cruciger (Thomas, 1892) is a Critically Endangered langur subspecies that has rarely been studied due to the difficulty of encountering it in the wild. Previously, this subspecies was sighted in Maludam National Park, Sarawak, Malaysian Borneo. Here, we provide the first sighting record of P. c. cruciger in Jemoreng Protected Forest in Sarawak, where a total of eight groups were observed. We urge for further comprehensive studies and immediate conservation action

A machine learning framework to classify Southeast Asian echolocating bats

Bats comprise a quarter of all mammal species, provide key ecosystem services and serve as effective bioindicators. Automated methods for classifying echolocation calls of free-flying bats are useful for monitoring but are not widely used in the tropics. This is particularly problematic in Southeast Asia, which supports more than 388 bat species. Here, sparse reference call databases and significant overlap among species call characteristics makes the development of automated processing methods complex. To address this, we outline a semiautomated framework for classifying bat calls in Southeast Asia and demonstrate how this can reliably speed up manual data processing. We implemented the framework to develop a classifier for the bats of Borneo and tested this at a landscape in Sabah. Borneo has a relatively well-described bat fauna, including reference calls for 52% of all 81 known echolocating species on the island. We applied machine learning to classify calls into one of four call types that serve as indicators of dominant ecological ensembles: frequency-modulated (FM; forestspecialists), constant frequency (CF; forest-specialists and edge/gap foragers), quasi-constant frequency (QCF; edge/gap foragers), and frequency-modulated quasi constant frequency (FMqCF; edge/gap and open-space foragers) calls. Where possible, we further identified calls to species/sonotype. Each classification is provided with a confidence value and a recommended threshold for manual verification. Of the 245,991 calls recorded in our test landscape, 85% were correctly identified to call type and only 10% needed manual verification for three of the call types. The classifier was most successful at classifying CF calls, reducing the volume of calls to be manually verified by over 95% for three common species. The most difficult bats to classify were those with FMqCF calls, with only a 52% reduction in files. Our framework allows users to rapidly filter acoustic files for common species and isolate files of interest, cutting the total volume of data to be processed by 86%. This provides an alternative method where species-specific classifiers are not yet feasible and enables researchers to expand non-invasive monitoring of bat species. Notably, this approach incorporates aerial insectivorous ensembles that are regularly absent from field datasets despite being important components of the bat community, thus improving our capacity to monitor bats remotely in tropical landscapes

Survey on the Small Mammals in Sg. Kangkawat Research Station Imbak Canyon Conservation Areas

Sg. Kangkawat Research Station is a newly established research station in the Imbak Canyon Conservation Area, Sabah which encompasses both primary and secondary forest areas. Limited data is available on the small mammal diversity for this particular area. Therefore, a survey-based study on small mammal diversity was carried out between the 29th September – 8th October 2018 along the established trails within the vicinity areas of this research station. Small mammal trapping was done using traps (mist nets, harp traps, cage traps and pitfall traps) employed randomly along the Nepenthes trail, the Kawang trail, the South Rim trail and the Pelajau trail. This study documented a total of 32 small mammal species i.e. represented by 26 species (15 spp. of new records for ICCA ) of volant small mammals (Chiroptera) and 6 species of non-volant small mammals (Rodentia, Scadentia, Insectivora, Carnivora). The total number of specimens recorded was 108. A new distribution record on the Free-tailed Bat, Chaerephon cf. johorensis, was documented for Sabah and Borneo during this study

ChiroVox : A public library of bat calls

Recordings of bat echolocation and social calls are used for many research purposes from ecological studies to taxonomy. Effective use of these relies on identification of species from the recordings, but comparative recordings or detailed call descriptions to support identification are often lacking for areas with high biodiversity. The ChiroVox website (www.chirovox.org) was created to facilitate the sharing of bat sound recordings together with their metadata, including biodiversity data and recording circumstances. To date, more than 30 researchers have contributed over 3,900 recordings of nearly 200 species, making ChiroVox the largest open-access bat call library currently available. Each recording has a unique identifier that can be cited in publications; hence the acoustic analyses are repeatable. Most of the recordings available through the website are from bats whose species identities are confirmed, so they can be used to determine species in recordings where the bats were not captured or could not be identified. We hope that with the help of the bat researcher community, the website will grow rapidly and will serve as a solid source for bat acoustic research and monitoring