Indian Institute of Science Education and Research-Pune
We received our SM4BAT recorders and an Echo Meter Touch 2 Pro in early February, and have been hard at work getting them tested and recording bats in Pune, prior to fieldwork in the Himalayas. First, we tested each of the recorders overnight on the IISER Pune Campus, and recorded a great deal of bat activity as the weather warms up! We have trained a student volunteer, Ram Mohan, in the use of these bat detectors and in basic analytical tools, and he will play a major part in this season's fieldwork. To get our educational and outreach activities started, we also conducted a bat walk on campus using the Echo Meter Touch 2 Pro. During both these activities, we identified and recorded calls of at least five bat species, including the Indian pipistrelle (Pipistrellus coromandra), the greater yellow house-bat (Scotophilus heathii) and the Egyptian free-tailed bat (Tadarida aegyptiaca).
All the other equipment for fieldwork has also been procured, and RC has now left for the Himalayas in Uttarakhand to begin our first field season. This work will last until mid-June at least, and will involve both our student volunteer and two field assistants (both of whom will also be trained in the use of recorders). Fieldwork from now on will focus on identifying suitable recording sites at four different elevations and getting acoustic data. Bat activity is likely to pick up by late March, so hopefully we will gather useful data on distributions and activity patterns soon!
In mid-March we were into the most anticipated leg of our project: field work! We reached Kedarnath Wildlife Sanctuary on 13 March and conducted fieldwork up till 15 May. After nine days of reconnaissance, we had finalised our recording sites. In order to have coverage of various habitat types and species, we placed our recorders in three habitat types: forest, forest edge and open areas. Our sampling locations also covered an elevational gradient from 1400 to 3700 m above sea level. Depending on the area of the sampling location and the habitat heterogeneity at various elevations, we had up to three spatial replicates of each habitat type. A breakdown of our recording sites is given in the following table. We recorded for two consecutive nights at each recording site. Assuming the night length to be 10 hours on an average, we collected roughly 760 hours of acoustic data!
During the course of fieldwork, we trained our field assistants Zareef Khan Lodha and Baseer Baniya Gujjar. Zareef and Baseer are from a small village in Uttarakhand and have been assisting biologists for the last five years. We have trained them in all aspects of bat research, and they are now well-trained not only in setting up bat detectors but also in identifying different genera of bats from recordings!
We are now back at IISER Pune and we have started analysing the recordings. Our intern, Ram Mohan is playing an important role in this step. Preliminary checks suggest that we have recorded about 15 species of bats across the elevational gradient, including the highest elevation record of the European Free-tailed Bat (Tadarida teniotis). We also have possibly the first recordings of social calls of bats from the Himalayas. We cannot wait to unravel more exciting distribution and activity patterns!
After the end of this year’s field work, we have been busy getting the data labeled and analyzed. Our intern, Ram Mohan, has been heavily involved in this aspect of the research up until the completion of his internship in August. The work has involved digitizing a call library of bats mist-netted during fieldwork. In order to recognize the species that has been detected during acoustic monitoring with the SM4BAT recorder, we must first reference the call to a known species. This is especially critical for bats, a poorly studied group whose calls remain largely unknown. In addition, their nocturnal habits make it impossible to identify vocalizing species without mist-netting them. Therefore, we mist-netted, identified and recorded bats during fieldwork, and have now digitized a call library to use as a reference for acoustic identification.
Our count indicates the presence of at least 13 species of bat across our study sites. From these calls, we calculated a set of 10 frequency and temporal parameters, and this combination of parameters serves as a signature that can be used to detect the presence of a particular species whenever it shows up in our SM4BAT recordings. We are now in the process of labeling bat detections within the larger monitoring dataset collected using the SM4BAT. So far, we have analyzed one night of recording each from 8 different sites, and have found 219 individual bat detections, an average of approximately 3 bat detections per sampling hour. The maximum detections so far have been from recordings made during the dusk and dawn hours, indicating an activity peak during those hours.
About half the SM4BAT data still remains to be digitized, following which we will reference labeled bat call to the call library using a custom tools and semi-automated routines. This will allow us to identify, to the best possible resolution, which species of bat are present at each site, and at what times of night. Thus, using a call library allows us not only to build an acoustic space within which we can identify bat species to a reasonable degree of confidence, but also allows to examine how multiple species of echolocating bat interact with each other across this montane ecosystem.
A European Free-tailed Bat (Tadarida teniotis) recorded at Tungnath, graphed using Raven Pro 1.5.0 (Cornell University, Ithaca, NY, USA).