WRITTEN BY MEG COOKSON

Bat field trip to Karnataka

 

If I just posted the endless species list that I collated over last weekend I think it would more than hint at the insane biodiversity Bhimgad Wildlife Sanctuary held, taking up at least two or three densely-packed pages in my field notebook (and these are just the ones identified onsite). However, to give more context than badly spelled latin names and quick notes like ‘up that big hill’ and ‘in the second river I went for a wee near’, I’d like to paint a prettier picture for you because it’s also something I never want to forget myself and better to get that down on paper as soon as possible.

Enter Wild Otters. Keen to learn. Equipped with binoculars, bat detectors and an unrivalled sense of purpose, we were going to study the bats and other creatures populating Bhimgad Wildlife Sanctuary in Karnataka. Nestled in the Western Ghats hills bordering Goa, the 73 square miles of tropical and subtropical broadleaf protected forest hosts numerous endemic plants and animals, whilst acting as a vital tiger corridor between three areas - the Anshi- Dandeli Wildlife Sanctuary, the Radhanagiri Wildlife Sanctuary and Mollem National Park. This incredibly important ecosystem also boasts the Barapede caves, the first discovered home to a rare and unique bat species – the Wroughton’s free tailed bat (Otomops wroughtoni). It has been recorded in only two other locations, Meghalaya in Northern India and the Preah Vihear Province in Cambodia lending to a ‘Data Deficient’ IUCN status with a distinct lack of ecological knowledge surrounding the species. It was my self-appointed mission to record the call of this white-banded, dusty-pink, fawn-coloured creature.

 
 
 
Figure 1 - The Wroughton's free-tailed bat (Otomops wroughtoni) is an extremely rare species of free-tailed bat (Molossidae), formerly considered to be confined to one cave in the Western Ghats. Photos by Jasper Maberly.
 

This weekend was to be remarkable for a number of reasons – other than the general excitement of exploring a true biodiversity hotspot, Wild Otters were to sign papers which would mean official collaboration with BCIT (Bat Conservation India Trust), a respected non-profit organisation conceived for the protection of bat species and their habitat in India, headed by Mr. Rajesh Puttaswamiah. Our shared goal was to create a complete frequency database of Indian bat’s species-specific echolocation calls which would enable and supplement diversity research throughout surrounding regions. Currently, there is no publicly accessible such database for surveying bats throughout India and we were to begin research together that day.

 
 
Figure 2 - Wild Otters team and BCIT signing their MOU's. L to R - Jasper Maberly, Isha Tickoo, Meg Cookson, Katrina Fernandez of Wild Otters and Rajesh Puttaswamiah of BCIT. Photos by Rajesh Puttaswamiah.
 
 

It felt like the second we entered the park, five of us bouncing around in the cab of a pick-up truck laden with tents and multiple packs of deep-fried Indian snacks, that we were hit with the sheer density of wildlife. A glance into the dense vegetation on your right revealed a herd of inquisitive (and mighty intimidating standing at 7-foot-tall) Gaur. Turn left and you were startled by a Grey Hornbill swooping down to land on a broken tree which was surrounded by several large tarantula nests. A couple of minutes down the road and a Green Vine Snake boldly confronts the truck, not phased at all by screeching tires and four enthusiastic researchers leaping out to closer inspect his lime luminosity. With the car engine off, the rising crescendo of (what felt like) a thousand cicadas quickly encompassed us, pressing us to raise our voices in a discussion of the snake’s death wish.

Back on the road again, the dappled sunlight of the afternoon’s leisurely crawl upwards made way for looming dense grey cloud welcoming us to our camp hosted by the anti-poaching unit of the Wildlife Sanctuary. In this season in Goa, there is practically no chance of rain but here, 2,600 feet up, the Western Ghats intercepts the winds arriving from the Arabian Sea which can cause heavy rainfall. The intense smell of rain only served to speed the unloading up. I don’t think I’ve ever put a tent up so fast.

 
 
Figure 3 - Common Vine Snake (Ahaetulla nasuta). One of the most ecologically significant and abundant snake species in the Western Ghats. Photo by Jasper Maberly
 
 

The journey to the cave from the campsite was short. Rajesh pointing out a plateau which the Wroughton’s free-tailed used as a major foraging site – a perfect place to record once the bats had emerged. The cave itself was not very deep but hosted a variety of eerie cave-dwelling species, including cave crickets, spiders, fleas, mites and cockroaches. The bat’s thick layer of faeces (guano) is a nourishing vital food source for many of these cave critters but was especially cherished by the many species of beetle who prevent this cave from filling entirely with the substrate. Standing still for too long is therefore never an option in these habitats (ticks are also rife) so we quickly got to exploring the gaps in the cave’s roof and walls. Straight away, four Pipistrelles cosied up in a nook... then, three Lesser False Vampire bats in the next cranny. A Rufous Horseshoe or two later… along with the Wroughton’s, it was almost too good to be true. We began recording their calls using the bat detector as the evening descended, watching them all ‘test’ the air as most bat species do; dropping out of their crevices, wheeling around to check the temperature, humidity and light levels are just right before quickly reentering to postpone leaving for the night a little longer.

 
 
Figure 4 - A group of Pipistrelles (Pipistrellus sp.) cuddled in a crevice at the roof of the cave. Photo by Jasper Maberly.
 
 

Once happy with the amount of distinct calls for each species we had accumulated, we climbed back up to the plateau to watch the Wroughton’s pursue the innumerable moths above our heads. The crystal clear night revealed the race between predator and prey, with various measures of ‘oohs’ and ‘aahs’ as the bat detector exposed the hidden workings of the Wroughton’s incontestable efficiency.

In other areas (namely the southwestern United States), having been predated on in this merciless fashion for thousands of years, a tiger moth species has evolved to produce it’s own signal which ‘jams’ the bats calls, interfering with the bats' neural processing of the returning echoes. It does this using organs called ‘tymbals’ which produce a rattle-like sound, confusing the bats and allowing the moth to escape. It is likely there are many more species who have evolved similar evasive techniques in this evolutionary arms race.

Rajesh had brought a mist net so we could begin to identify species more accurately using morphological measurements as well as acoustic. Basically a large expanse of fine nylon mesh, the net towered above us at 6 metres tall and 12 metres wide – held up by two extendable poles and hoisted onto the back of our two pick-up trucks which were parked parallel across a forest corridor. Corridors such as this one are crucial components of a bat’s preferred environment. Similar to hedges and hedgerows they provide connectivity, allowing bats to move easily through the landscape to different habitats. They are essential for a bat’s commuting route to water sources or foraging areas miles away and in the case of fruit bats that commuting could be up to 50km per night. Furthermore, the proven overarching ecological usage of these areas by bugs and fruiting trees alike means that they are likely to host a wide diversity of bat species both insectivorous and frugivorous, so it was a prime location for our netting research and we were excited to come across such a perfect placement, eagerly awaiting the first stirring of the net, headtorches at the ready.

 
 
Figure 5 - Two trucks held our mist nets at a perfect height to net low flying species of bats. Photo by Rajesh Puttaswamiah
 
 

Over the course of the evening, we netted one pipistrelle species and two horseshoe bats and recorded a variety of other species including a potential mouse-tailed bat – these were kept for later analyses using the frequency database. Length measurements such as the forearm, tragus, tibia and metacarpals were carefully taken, all lending to a more accurate species identification. Free-tailed and tomb bats are notoriously high fliers (with the Brazilian free-tailed bat clocking 3,300m in altitude!) so we only captured low flying species – one of the disadvantages of mist netting. This is why using two methodologies (such as recording calls and netting) has been proven to be key when accurately completing diversity studies.

Our stomachs now rumbling (we had forgotten to bring snacks – rule 101 of long hours in the field), we took down the nets and trundled back to the camp truly spent, but happy.


References:

Ruedi, M., Mukhim, D., Chachula, O., Arbenz, T. and Thabah, A., 2014. Discovery of new colonies of the rare Wroughton’s Free-tailed Bat Otomops wroughtoni (Mammalia: Chiroptera: Molossidae) in Meghalaya, northeastern India. Journal of Threatened Taxa, 6(14), pp.6677-6682.

Srinivasulu, C., Racey, P. and Mistry, S., 2010. A key to the bats (Mammalia: Chiroptera) of South Asia. Journal of Threatened Taxa, 2(7), pp.1001-1076.

Toffoli, R., 2016. The Importance of Linear Landscape Elements for Bats in a Farmland Area: The Influence of Height on Activity. Journal of Landscape Ecology, 9(1), pp.49-62.