Bats In The Land Of Hornbills
Exploring every chiropterologist’s dream destination of Borneo, Rohit Chakravarty makes the ultimate bat lover’s pilgrimage – to the Gunung Mulung National Park. “Bamboo bat!”
Photo: Rohit Chakravarty.
My eyes gleamed when I heard that and I rushed for the bats, which were hanging in cloth bags. I gently rubbed my fingers on the outside of each bag and picked the one with the smallest bat. I delicately removed the flying mammal, holding it with just the tips of my first three fingers. This was no ordinary bat. Its head was flat as if slammed with a shoe! It also had suction pads on its thumb and toes to help it cling to and sleep inside thin, hollow bamboo culms. The bat in my hand was an evolutionary marvel. The lesser bamboo bat Tylonycteris pachypus marked the beginning of a successful night. After it, eight other species flew into our nets in quick succession. Borneo was beginning to justify itself as a chiropterologist’s dream destination.
In August 2015, I was in Sarawak to attend the 3rd Southeast Asian Bat Conference organised by Universiti Malaysia (UNIMAS), Sarawak, and Southeast Asian Bat Conservation Research Unit (SEABCRU). After four intense days of talks, discussions and workshops with the most renowned bat biologists of the world, we were off on a bat lover’s ultimate pilgrimage – Gunung Mulu National Park.
Southeast Asia is one of the top biodiversity hotspots in the world. And Borneo – the third largest island in the world – is undoubtedly the jewel in its crown. The World Wide Fund for Nature (WWF) estimates that more than 220 species of mammals, 420 species of birds, 200 reptiles and amphibians, and close to 400 species of fish are found in Borneo. A part of this staggering diversity comprises iconic, threatened species like the Bornean orangutan, Bornean pygmy elephant, proboscis monkey and Hose’s palm civet, all found nowhere else on Earth. Eight species of hornbills occur here and it is after them that the state of Sarawak in Malaysian Borneo derives its apt title – Bumi Kenyalang – The Land of the Hornbills. However, unbeknown to many, the major contributors to the mammalian diversity of this incredible island are bats. With roughly 90 species, bats make up about 40 per cent of all the mammals found in Borneo. Once you set foot in Gunung Mulu National Park, you understand why.
Photo: Rohit Chakravarty.
A bat paradise
Gunung Mulu National Park, a UNESCO World Heritage Site, is the most spectacular landscape that I have seen. Around 20 million years ago, this stunning forest was an underwater mountain. Five million years ago, tectonic activity brought the mountain above water. Today, this has metamorphosed into a lush-green rainforest criss-crossed by rain-fed rivers through which emerge jagged limestone mountains that give Mulu its unique prehistoric setting. When rainwater touches limestone it dissolves the rock to form caves. Undulating limestone hills and heavy rainfall are therefore characteristic of Mulu, which is blessed with countless cave systems. Such is the vastness of this pristine and rugged limestone forest that it took 15 months and 115 scientists of the Royal Geographic Society, U.K., just to map its topography in 1977-78!
We arrived in Mulu in the afternoon of August 18, 2015, to assist student-researchers from UNIMAS in their study of Mulu’s bats. On arrival, Ellen McArthur, a masters student working on the bats, greeted us with the delightful news that she had found something special for us during her routine morning reconnaissance. I whiled away my time watching birds and a hungry Prevost’s squirrel gorging on leaves at the canopy until it was time to go bat hunting. Ellen led us to the nature trail and after walking barely a kilometre, she stopped abruptly in front of a wild turmeric plant. Neatly hidden inside a young, rolled-up leaf was a tiny bat. High on my wishlist – the diminutive Hardwicke’s woolly bat Kerivoula hardwickii weighs barely three or four grams. Its body is densely covered with sooty-black, woolly hair. What makes this bat sui generis is its recently-discovered symbiotic association with a carnivorous pitcher plant Nepenthes hemsleyana. In the nutrient-poor peat swamp forests of Borneo, the pitcher has evolved to attract these bats, but the plant does not kill them. Instead, the plant provides lodging and the bat pays its rent by feeding the plant with its nitrogen-rich droppings! Hardwicke’s woolly bats are also the supreme sopranos of the animal world. Their ultrasonic calls start at 250 kHz – that’s 12 times higher than humans can hear!
Photo: Rohit Chakravarty.
The following evening, I had a date with a glorious natural phenomenon; one that I had, hitherto, only seen on television. At 3.30 p.m., a crowd assembled at the ‘Bat Observatory’ outside Deer Cave. The largest cave chamber in the world, Deer Cave is home to an estimated three million wrinkle-lipped bats Chaerephon plicatus. As dusk approached, the anticipation built up at the observatory. I saw a handsome Bat Hawk perched on a vantage point, its eyes fixed on the mouth of the cave. Suddenly a cheer rose from the audience; the bats had begun to emerge en masse. One after the other, clouds of bats flew out of the cave in perfect synchrony like a flock of starlings. Each group formed a different pattern in the sky – ribbons, waves, ‘S’ and even a moustache! It was time for the Bat Hawk to launch its first strike (a success) right in the middle of the bat cloud. At the mouth of the cave, I also briefly saw a large eagle, probably a Wallace’s Hawk Eagle trying to intercept emerging bats. Watching the phenomenon on television was breathtaking enough even before I got interested in bats, but seeing the drama unfold before my eyes was a dream come true.
On our last night in Mulu, we doubled our efforts to catch bats. A mist-net (a thin nylon net used to catch birds and bats for research) was spread on a bridge over a river. An ingenious trap called a ‘harp trap’ was set up along a forest trail. This trap has metal frames with fine plastic strings stretched to full tension and placed in parallel rows as in a harp (hence the name). The frame sits on four legs and a collection bag is placed at its base to allow a safe landing for bats that hit the strings. The bats are then picked up from the bag to be identified. Harp traps are particularly effective for strictly forest-dwelling bats that often detect mist-nets by ultrasound. One of us was also deployed with a hand-held hoop net to catch bats flying in the open air. Ours was a truly global bat trapping team with representation from nine countries! We caught several species that night. Our mist-nets revealed wrinkle-lipped bats that love feeding over wide rivers. They are the most gentle and docile of all bats that I have handled. A not-so-docile bat was the one caught in the hoop net by my Hungarian friend, Tamas Gorfol – a Diadem’s leaf-nosed bat Hipposideros diadema. This is a large bat that typically hawks insects in forest clearings. Its body is a rich beige or orange with characteristic white patches on the flanks. At the harp trap, we caught the Cantor’s H. galeritus and fawn leaf-nosed bats H. cervinus and my favourite, the large-eared horseshoe bat Rhinolophus philippinensis. This is a dense forest species, with large leaf-shaped ears and a peculiar nose that emerges like a unicorn’s horn. Back at the base, another team examined a pretty, spotted-winged fruit bat Balionycteris maculata – a small and timid black bat with chicken pox-like spots on its wings. The best, however, was saved for the last, the miniscule least woolly bat Kerivoula minuta, so tiny that when Tigga Kingston – a leading bat biologist – passed it on to me, she said, “Be careful, you’ll have to hold it like a grain of salt!” A strict inhabitant of primary forests, habitat destruction, unfortunately, has put Kerivoula minuta in the threatened category.
Photo: Rohit Chakravarty.
Bats of India
With more than 120 species, bats are the largest group of mammals in India. Naturally, when there are so many species, there is a great and amusing diversity of shapes and sizes. There are bats that look like foxes, some that look like mice and others that have bizarre noses. Two main types of bats are found in India – one that eats fruits and the other that eats insects. There are also false vampire bats, which are carnivorous and hunt small animals. Bats find their way by producing ultrasound. The frequencies at which different species call can be recorded using an ultrasound recorder called a ‘bat detector’, which can help in species identification. Fruit bats act as gardeners by pollinating flowers and dispersing seeds of several tropical trees. Insectivorous bats, on the other hand, are voracious eaters and efficiently control many nocturnal agricultural pests.
On the flight back to Kuching, I reflected on the immensely thrilling and educative days spent in Mulu. Looking out of the window, I saw a bald patch smack in the middle of the verdant rainforest. There are several such threats that bats face globally. Deforestation impacts forest-dwelling bats. Granite and limestone mining affects cave-roosting species. Recent studies suggest that windmills kill more bats annually than almost any other man-made device. Clearly more research will come up with grimmer results. Our own personal attitudes that stem from superstitious beliefs and myths prevent us from appreciating the crucial role that bats play in maintaining natural ecosystems. In Southeast Asia, hunting and destruction of vast swathes of prime rainforest are undoubtedly the single largest threat to bats. In recent years, ever-increasing logging and oil palm plantations have ravaged the magnificent Southeast Asian rainforests with catastrophic impacts on orangutans, elephants, bats and even its indigenous tribes.
Photo: Rohit Chakravarty.
Should this be of concern only to anthropologists and ecologists? With the world running out of time and climate change hovering over our collective heads like the sword of Damocles, it would be mankind’s greatest cataclysm to allow 140-million-year-old rainforests and other equally miraculous natural ecosystems to be imperilled by little more than our lifestyle choices and by political ignorance.
Author: Rohit Chakravarty, First appeared in: Sanctuary Asia, Vol. XXXVII No. 8, August 2017.