Thai Adventures Part 3: Cave Bats

12/26/19

By Daniel Hargreaves

We arrived at sunset at the OurLand Nature Reserve in Kanchanaburi Province, our home for the next 5 days. We quickly set up a few mist nets and a harp trap and were rewarded with a brace of lesser false vampire bats (Megaderma spasma) and several cave nectar bats (Eonycteris spelaea). Merlin took the opportunity to show the group how to train a bat. Unfortunately, the chosen bat was unusually difficult. However, just over an hour later it eagerly permitted Merlin to approach, enticing it to drink from a syringe filled with sugar water.

The next morning, we climbed 200 steps in search of roosting bats located in two caves above a monastery occupied by Buddhist shrines.

Group climbing the steps to the cave with Kate in the lead.
Group entering cave.
Daniel Hargreaves showing the first tiny bumblebee bat to our group.

Initially, we captured a long-winged tomb bat (Taphazous longimanus) but as the group was looking at that one, I netted two bumblebee bats (Craseonycteris thonglongyai). Both were females weighing around two grams. They were delicately held by group participants while I explained the species’ anatomy, ecology, and conservation status.

Mindy excited to be holding a famously tiny bumblebee bat.

For several people, seeing this bat was a lifelong ambition as it is widely reputed to be the world’s smallest mammal. Nevertheless, as Merlin explained, several bats and a shrew are contenders for this distinction which cannot be resolved until more detail is obtained on annual weight cycles. The contenders are all close to two grams, plus or minus just a half gram! After several photos, the bats were filmed departing for secret recesses.

We next descended deeper inside where we found a group of great roundleaf bats (Hipposideros armiger) and observed as they “boxed” and jostled for social position. These large bats do not need to cluster to share warmth and are likely aided by a combination of body size and warmth of their caves. In fact, each strongly defends a minimum space from its nearest neighbor.

Great roundleaf bats roosting.

In the evening we set nets and traps again in the OurLand reserve and captured five species: one cave nectar bat, four lesser false vampire bats, one greater false vampire bat (Lyroderma lyra) and two new species for the reserve, one croslet horseshoe bat (Rhinolophus coelophyllus) and one eastern bent-winged bat (Miniopterus fuliginosus).

Lesser false vampire bat.
Greater false vampire bat.
Croslet horseshoe bat.
Eastern bent-winged bat.

Merlin demonstrated to the group how he takes his iconic portraits of bats and one lesser false vampire bat was kept for training. While sitting in the small training tent, Kate fed the bat mealworms and slowly gained its trust.

An early start had us riding in dragon boats down the famous River Kwai to a remote cave along the border of Sai Yok National Park.

Dragon boat trip down the River Kwai. Cyndi, Kate and Alyson in foreground.

Following a 30-minute journey, we stopped and decided to hike the remainder of the way. A stream stood between us and the cave so, after finding a shallow point, we all waded across and up into the jungle.

Preparing to cross jungle stream. Brian, Alyson, and Carla midway.
Mindy hiking to remote cave.

The cave sheltered several bumblebee bats and the much larger, great roundleaf bat. I netted one of each to demonstrate the size difference between the species.

Daniel Hargreaves showing large wing of a great roundleaf bat while Daniel Whitby compares the much smaller wings of a bumblebee bat found in the remote border cave.

Several of us crawled through a tight squeeze into a larger chamber where we found the floor littered with the remnants of prey caught by a greater false vampire bat. On the hike back we each enjoyed a refreshing green coconut drink from a local farmer before getting back onto the dragon boats and heading home for lunch.

Drinking coconut juice along return hike to dragon boats. Kate, Alyson, Pongsanant, and Daniel Hargreaves in foreground.
Lunch in a roadside café. Gretchen and Bruce in foreground.
Boarding dragon boat for return trip up the River Kwai.

After lunch we drove a short distance past a Buddhist temple courtyard to explore a large limestone cave with many outcrops.

Buddhist shrine en route to Cave.
Entering the Cave. Melanie and Kate in the lead.
Group inspecting shrines at the cave entrance.

Guarded by the large shrines, we found groups of greater short-nosed fruit bats (Cynopterus sphinx) roosting in ceiling domes.

This is unusual behavior for this genus, something Merlin had not seen before. He speculated their yet undiscovered ability to echolocate. How else could they find a small dome in the ceiling on a dark night, some 60 feet from the entrance? Farther inside we found groups of lesser false vampire bats, bumblebee bats, and intermediate roundleaf bats (Hipposideros larvatus). 

Daniel Hargreaves sharing a greater short-nosed fruit bat.
Melanie, Carla, and Leanne photographing relatively tame lesser false vampire bats, aided by Daniel Whitby. Bats protected in caves with shrines often learn to ignore passing humans.
Daniel Whitby showing a lesser false vampire bat to Kate and Gretchen.

That evening, we set nets close to the river and along forest trails back at the reserve. We caught several more lesser false vampire bats and a single greater false vampire bat.  

Following a hearty breakfast, our hosts at the OurLand reserve provided an outstanding introduction to the area’s snakes. Among other things, they demonstrated that although highly venomous, cobras are actually quite reluctant to bite.

Hosts demonstrating cobra’s preference for bluffing (hood expanded and hissing) instead of biting.
Meeting a tame python.

Following the snake demonstration and a short drive, we visited a different cave owned by another monastery. The monks had built concrete stairs that included 340 steps up a steep ridge to the cave. We enjoyed the view over the valley, but not the climb.

Cyndi and Carla nearing the top of the stairs.
A rest stop inside the cave entrance.

Nevertheless, this vast cave was well worth the extra effort! Close to the entrance we found hundreds of roosting Theobald’s tomb bats (Taphozous theobaldi). Leanne captured several with a hand net to give the group a closer look. We then found several more species, including the area’s ever-abundant bumblebee bat, intermediate roundleaf bat, and the not-previously-seen large-eared roundleaf bats (Hipposideros pomona) and Dobson’s horseshoe bats (Rhinolophus yunanensis).

Carla inspecting a Theobold’s tomb bat.
Daniel helping Mindy, Kate, and Melanie identify a Dobson’s horseshoe bat.
Melanie helping Carla photograph the Dobson’s horseshoe bat.
Carla, Kate, and Jeanette photographing bats inside the cave.

After a late lunch and brief rest we returned, this time climbing the 340 steps with over 100 kilograms of camera equipment. The steps seemed to have grown longer!

We set up a light beam in a narrow spot where exiting bats would have to pass prior to emerging from the cave. We then helped a half-dozen group members position their cameras on tripods, aimed and focused on the beam. As emerging bats struck the beam, everyone got a photo. We shot hundreds of photos of several species before climbing back down the steps in the dark.

A large-eared roundleaf bat in flight.
A bumblebee bat in flight.
A Rhinolophus bat checking us out!

Soon after arriving back at camp we built a set in Merlin’s studio, mimicking the surrounding habitat and forest floor. A half dozen of us positioned our cameras on tripods, again focused on the beam to catch our tamed lesser false vampire bat flying through as it would if hunting.

Bruce, Merlin, Daniel Hargreaves, Brian, and Daniel Whitby, each with a camera poised to catch a lesser false vampire bat flying through a set.

Lesser false vampire bat in flight.

Once finished around midnight, all was disassembled, the now well-fed bat released, and Merlin’s studio packed in preparation for the next morning’s departure. Whilst everyone else slept, I could not resist staying up to photograph a cave nectar bat pollinating banana flowers outside the dormitories.

Cave nectar bat feeding from a banana flower in the wild.

We waved goodbye to our hosts at OurLand and visited one final cave in Kanchanaburi. The cave was hidden on the grounds of a Buddhist monastery and after we gained permission to enter we passed several shrines and large ornate statues. Once we entered the cave, I quickly helped Merlin set up three flashes on stands to photograph a bumblebee bat hanging from my fingers. He wanted to illustrate its tiny size.

The group explored the cave and found a colony of roundleaf bats roosting high in the cave ceiling and a new species for the trip–a Pearson’s Horseshoe bat (Rhinolophus pearsonii)–roosting in a colder part of the cave. Once Merlin had the photos he needed, the group loaded up the vans and we continued our journey South to Ratchaburi.

Daniel helping Merlin photograph a bumblebee bat in a hand inside the Cave.
Bumblebee bat in hand.

NOTE: None of the cave-dwelling bats we handled were reproductively active or attempting to hibernate. They were netted by experts, handled gently, and released promptly at points of capture.