Keywords

15.1 Introduction

The northeastern part of India is a biological treasure trove and the state of Meghalaya is no exception. Being a part of Indo-Burma biodiversity hotspot (Mittermeier et al. 2004), the state exhibits exceptional diversity and endemism of life forms including over 60 species of bats which comprises about 50% of the 125 bat species known from India (Talmale and Pradhan 2009; Ruedi et al. 2012a, b; Senacha and Dookia 2013; Saikia et al. 2017; Thong et al. 2018).

The extraordinary opulence of life forms in Northeast India as a whole can be attributed to a complex variety of factors like geologic age, past and present climatic conditions, geographic location at the confluence of different biogeographic realms, unique zoogeographic history, etc. (Pawar et al. 2007). Meghalaya harbours numerous caves and caverns of which 925 are scientifically explored and mapped (Arbenz 2013).Caves serve as a major roosting place for a large variety of bats since it offers relatively stable microclimate, insulate them from environmental stochasticity and release predatory pressure. Availability of suitable roost is a critical factor that largely determines diversity and distribution of bats (Arita 1993; Kunz 1982). Thus, the state with abundant caves and caverns especially in the limestone belt offers unlimited roosting opportunity for a large variety of bats.

The zoogeographic chronicle of Northeast India as a whole is very fascinating. Situated at the confluence of Indo-Malayan and Indo-Chinese subregions and also juxtaposed to the Palearctic realm (Rao 1994), the faunal composition of northeastern India is complex and composed of elements from the above regions. Northeast India is hypothesized as a gateway for faunal influx from the neighbouring region to mainland India especially the Indo-Malayan and Indo-Chinese fauna (Kurup 1968). Likewise, many of the Palearctic and Indian animal species were supposedly extended to the Southeast Asian region through the northeast Indian corridor (Kurup 1974). This region possibly served as a refugium for flora and fauna during Cretaceous isolation of Indian subcontinent leading to evolution of endemic taxa (Kamei et al. 2012). The Meghalaya subtropical forests ecoregion (IMO126) covering Meghalaya and the adjacent areas of Assam is recognized as one of the most species diverse regions for plants, birds and mammals (Wikramanayake et al. 2002). Unfortunately, this unparalleled biodiversity of the region is facing serious anthropogenic threats especially mining and deforestation which are magnified in recent times.

Compared to other states of Northeast India, the bat fauna of Meghalaya is relatively better known. This is primarily because of the fact that the provincial British administration was based at Shillong, the headquarters of erstwhile Assam Province and naturalists under the patronage of the British government conducted extensive faunal surveys in the Khasi and Jaintia Hills area. Edward Blyth, a British zoologist and curator of the museum of Asiatic Society of Bengal, first reported a collection of birds, mammals and reptiles from Cherrapunji in East Khasi Hills District. His report including the description of Nycticejus ornatus (=Scotomanes ornatus) possibly represents the first scientific record of bats from Meghalaya (Blyth 1851). British geologist and surveyor H. H. Godwin Austen surveyed Khasi and Jaintia Hills in the early 1870s and collected mammalian specimens later to be deposited in the Indian Museum, Calcutta. Subsequently, based on Austen’s and other’s collection in the museum, Edward Dobson, a British army surgeon and a mammalogist par excellence, provided scientific description of Rhinolophus garoensis (= R. subbadius), Phyllorhina leptophylla (= Hipposideros larvatus), Vesperugo (Vesperus) pachyotis (= Eptesicus pachyotis) and Pipistrellus austenianus (= Hypsugo savii) and also published a list of bats inhabiting Khasi Hills (Dobson 1871, 1872, 1874). During 1922, Stanley Kemp and his associates of Zoological Survey of India conducted extensive faunal exploration in Siju cave in South Garo Hills. They recorded Cynopterus sphinx, R. subbadius and Hipposideros lankadiva from the cave (Kemp 1924). As a result of the Mammal Survey organized by Bombay Natural History Society (1911–1923), extensive mammalian collection were made from parts of Khasi, Jaintia and Garo Hills by collectors like H. W. Wells, and the results were published in the Society’s journal. The report included some bat species from Meghalaya like R. affinis, R. lepidus, R. luctus, R. pearsonii, Scotophilus kuhlii, Leuconoe sp. (Myotis sp.), Scotomanes ornatus imbrensis, etc. (Thomas 1921; Hinton and Lindsay 1926). In the early 1950s, Walter Koeltz, an American zoologist and collector affiliated to the University of Michigan, made extensive mammal collection from Khasi Hills (Cherrapunji, Mawphlang, Mawryngkneng). His collections including many bat specimens are now mostly housed in the Field Museum of Natural History, Chicago, and the Museum of Zoology, University of Michigan. After a significant lull, Gyorgy Topal from the Hungarian Natural History Museum conducted bat surveys around Cherrapunji and reported the presence of Ia io and Myotis laniger in Meghalaya (Topal 1970, 1974).Consequently, Lal (1977) reported Rhinolophus macrotis from Cherrapunji area. Thereafter, Y. P. Sinha of Zoological Survey of India reported the occurrence of Eonycteris spelaea, Myotis longipes, Pipistrellus dormeri (=Scotozous dormeri) and Miniopterus schreibersii s.l. from Meghalaya (Sinha 1990, 1994, 1995, 1999a). Bates and Harrison (1997) in their comprehensive account included 50 species of bats from Meghalaya with a few species records now considered redundant. Sinha (1999a) documented the presence of nine species of bats from Siju cave, South Garo Hills. Thabah and Bates (2002) reported Otomops wroughtoni from a cave in East Khasi Hills District, Meghalaya, filling a major disjunction in distribution range of this species. Thabah (2006) conducted a study on the bat diversity of Meghalaya with special reference to caves in East Khasi Hills District. Of late, as an offshoot of an ongoing cave exploration project in Meghalaya, scientists have described two new species of bats, namely, Murina jaintiana and M. pluvialis, and also reported a few additions to the bat fauna of the state (Ruedi et al. 2012a, b). In addition, new roosting colonies of rare Otomops wroughtoni have also been reported very recently from the state (Ruedi et al. 2014). Our own ongoing field surveys further revealed the presence of several other species including some poorly known taxa in the state. In view of remarkable species diversity, scattered nature of information especially on distributional aspects and also the existential threat faced by these animals, the present communication aims to collate the available authentic information on diversity and distribution of bat fauna in the state.

15.1.1 Study Area

The state of Meghalaya is spread between 25002′ and 26007′ N latitude and 89049′ and 92050′ E longitude and encompass an area of 22,429 sq. km (Anonymous 2005).It is bordered by Assam state in the North, East and north-west and by Bangladesh in the South and south-west. Geologically, Meghalaya mostly consists of a stable structural block called the Shillong Plateau, hills of which rise to a maximum height of 1950 m. A sedimentary sequence called Jaintia Group which is a mixture of limestone, sandstone and coal lies South to Shillong Plateau (Tringham 2012). The state receives high annual precipitation with an average of 2689 mm in western Meghalaya and 7196 mm in the central and western Meghalaya (Haridarshan and Rao 1985). Due to high rainfall, the acidic rainwater absorbed in the ground react with the limestone and dissolves them. Ultimately, it creates an extensive network of underground drainage system, including caves, some of which run into several kilometres. Caves are developed intermittently along the whole limestone belt of the state and also in sandstone and quartzites areas of southern Meghalaya (Tringham 2012).The state has a recorded forest cover of 78.74% of the total geographic area of which 45.20% consists of very dense and moderately dense forest (FSI 2013). The vegetation in the state can be grouped into tropical forest, tropical evergreen forest, tropical semi-evergreen forest, tropical moist and dry deciduous forest, grasslands and savannas, subtropical pine forest and temperate forest (Haridarshan and Rao 1985).

15.2 Methods

The present account is a review of the published information on bat fauna of the state. Besides the published results, online collection database of museums abroad especially that of Field Museum of Natural History, Chicago, which houses a considerable collection of bat specimens from Meghalaya is also utilized for retrieving distributional information. This is supplemented by recent field surveys in Meghalaya state (2011–2018) and examination of voucher collections deposited at Zoological Survey of India, Shillong (ZSIS). A total of 511 specimens belonging to 31 species of bats from Meghalaya at ZSIS were examined and data incorporated in the present report. Recent bat surveys in the states were mostly conducted in the cave systems of Jaintia Hills area. Specimens were captured using mist nets and two bank harp traps. For most species where their identity could definitely be established in the field, individuals were released after morphological measurements and photographic documentation (mentioned here as pers. obs.). In case of doubtful species identification, few vouchers were taken and preserved in alcohol for further taxonomic studies.

15.3 Results and Discussion

15.3.1 Bat Diversity of Meghalaya

The latest account on the bat fauna of Meghalaya comprises 60 species belonging to seven families (Ruedi et al. 2012b). Some of the species in the inventory like Murina jaintiana and M. pluvialis have recently been described (Ruedi et al. 2012a), while a few others like Rhinolophus siamensis, Miniopterus magnater and Kerivoula kachinensis were newly reported from the state. This clearly underlines the scope for a much enhanced inventory with intensive field studies and robust analysis. Sinha (1995) reported Pipistrellus (=Scotozous) dormeri from Meghalaya following which it has been included in Ruedi et al. 2012b. This record was based on a partly damaged male specimen collected from Shillong (ZSIS Regn.No.V/M/ERS/270). However, examination of teeth (e.g. two upper bicuspidate incisors, myotodont lower molars) and external characters (e.g. relatively large and angular ears with elongated tragus, forearm 33.6 mm) of this specimen on which Sinha’s record was based revealed that it does not belong to S. dormeri but most probably represents another poorly known species, Hypsugo cadornae. Scotozous dormeri has therefore been excluded from the present report. Likewise, the doubtful record of Hipposideros ater from Cherrapunji in Kurup (1968) has also been omitted from the current inventory. Based on differences in echolocation call frequency and genetic divergence, Thabah et al. (2006) reported the existence of two cryptic taxa in the Hipposideros larvatus species complex in Meghalaya. They referred them as H. khasiana and H. grandis, respectively, but in the absence of designated type material, the former must be considered as a nomen nudum while the taxonomic position of the second is still debated. Before these two species are formally recognized, they are omitted in the present account and are included in the H. larvatus species complex. In view of recent taxonomic revisions and delineation of species boundaries, two species from earlier accounts, namely, Plecotus auritus (confined to Europe, Spizenberger et al. 2006) and Barbastella leucomelas (distributed in Western Asia, Benda et al. 2008), have been substituted with P. homochrous and B. darjelingensis, respectively. Similarly, all records of Miniopterus schreibersii from the Oriental region are based on a previous taxonomic concept considering that this species is polytypic and widespread across the Old World (Simmons 2005). As schreibersii is now clearly restricted to the Western Palaearctic region, populations of large Miniopterus from India should either be assigned to M. magnater or to M. fuliginosus (see, e.g. Appleton et al. 2004; Kruskop et al. 2012). For instance, based on measurements of specimens in ZSIS (e.g. mean forearm length 50.4 mm and mean skull length 16.6 mm), all reported specimens from Siju cave (Sinha 1999a) indeed represent Miniopterus magnater. Our own field observations also confirmed the widespread occurrence of M. magnater in the caves of Jaintia and Khasi Hills. The slightly smaller M. fuliginosus is also likely to be present in the region, although yet to be formally identified. During field surveys conducted in February 2015, we recorded the presence of another, much smaller species of Miniopterus at Umlyngsha village in Jaintia hills. Owing to its distinctly small forearm (43.0 mm) and delicate dentition, we assign this adult female specimen to M. pusillus and are thus reported here for the first time from the state. A few interesting pipistrelles were also captured in the same area including the uncommon Pipistrellus ceylonicus (adult female, forearm length 34.9 mm) and P. cf. paterculus (five individuals, mean forearm length 33.26 mm) which represent first mention of these species in Meghalaya state.

Our ongoing field surveys further revealed the presence of the greater bamboo bat Tylonycteris robustula in small bamboo groves near the village of Kharkhana in East Jaintia Hills. This species represents another addition to the chiropteran fauna of the state. Formerly, T. robustula was restricted to the eastern most parts of the Indian subcontinent (Bates and Harrison 1997). A recent taxonomic revision of genus Tylonycteris further shows that T. robustula is a species complex and the continental representative (including northeastern India) are referrable to the species T. malayana (Tu et al. 2017). A few significant recent bat records from the state include a very poorly known vespertilionid, the Joffre’s Pipistrelle Hypsugo joffrei. Previously known only by a few specimens from Myanmar and Vietnam, it has been found to occur in Shillong, and thus represents an addition to the bat fauna of India (Saikia et al. 2017). Besides this, the Szechwan Myotis Myotis altarium previously known from southeastern China and northern Taniland has also been reported from Cave Khung in East Jaintia Hills and Cave Arwah in East Khasi Hills districts of Meghalaya which also constitutes the newest addition to the bat fauna of India (Thong et al. 2018).

Recent winter surveys of bats in the Jaintia Hills further evidenced the presence of two uncommon species of Pteropodidae, Megaerops niphanae and Macroglossus sobrinus in Meghalaya. The former is being reported for the first time in Meghalaya, whereas the latter was known so far by only a single record from Umkiang, East Jaintia Hills (Das et al. 1995). Both of these species were recorded during the February 2011, 2013 and 2014 surveys in secondary forests with banana plantations near the villages of Kharkhana, Tangsen, Khahnar in East Jaintia Hills. Bats of the genus Cynopterus were also common in these secondary forest habitats, but their taxonomy in northeastern India is still uncertain (Chattopadhya et al. 2016). Besides the common C. sphinx and the rarer C. brachyotis, a further unnamed lineage may exist in Meghalaya. We indeed observed several individuals with morphological character combination that are not typical of either of these species, i.e. a large body size, ears without any pale borders, but further genetic comparisons are necessary before this new lineage can be reported on the species list. Thus, the following account (Table 15.1; Plate 15.1) provides an updated list of 65 species of bats in eight families known from Meghalaya along with distributional information.

Table 15.1 List of bat species authentically recorded from Meghalaya with distributional localities in the state
Full size table

15.3.2 Threats to the Bat Fauna of Meghalaya

The state of Meghalaya has huge reserves of mineral resources including an estimated 15,100 million tons of limestone and 576 million tons of coal (DMR 2015). While planned utilization of these resources can usher in economic prosperity for the state, unrestrained exploitation of the same for long periods has left indelible environmental footprint. The areas with extensive cave systems (which also support large populations of bats and other cavernicoles) harbour most of these mineral deposits and thus bring two sets of competing interest into close proximity and the resultant conflict. Mining in the state is often done using primitive sub-surface mining method without any environmental safeguards and post-mining treatment of mined areas which render the fragile ecosystems more vulnerable to environmental degradation (Tiwari 1996). To make the matters worse, the state government does not have much control over the land and resources of sixth scheduled areas, and mining in the unorganized sector is largely unregulated (Anonymous 2005).This is especially evident in Jaintia Hills region where unregulated coal mining has caused extensive deforestation and pollution of terrestrial and aquatic habitat and destruction of cave environment (Swer and Singh 2003). The Krem Lait Prah-Um-Im Labit cave system in Jaintia Hills recognized as the longest cave system in India is being threatened by indiscriminate coal mining in the nearby areas (Nayak and Bhattacharyya 2008). Also, there is high possibility of tectonic activities accentuated by surface mining resulting caving in of cave roof and annihilating the entire cavernicolous biodiversity. It is likely that cave Mawmluh in Cherrapunji will be destroyed in the near future because of longtime limestone mining by the adjacent cement factory (Biswas 2009; Daly 2013). There have been newspaper reports that illegal mining in the nearby areas is threatening the rich biodiversity of Siju cave in South Garo Hills, one of the most well-known bat caves in India. The biodiversity of Garo Hills region which is one of the last remaining strongholds of tropical forests of the Indo-Myanmar biodiversity hotspot is in great danger especially from conversion of forest land for road construction, farming, mining, etc. (Bera et al. 2006; Kunte et al. 2012). Undoubtedly, the bat fauna of the region especially the forest-dependent species are facing serious threat to their survival.

Widespread consumption of bat as bush meat poses another grave risk for the survival of bat populations of the state. While use of bat meat for purported medicinal value is prevalent among many communities in the North-East India (Hilaluddin and Ghose 2005), this practice is found to be particularly common in many rural areas of Meghalaya where bat meat is also consumed by the village people as a supplementary source of protein (Ruedi et al. 2012b; pers. obs.). During visits to Shnongrim, Piel Klieng Pouk and adjacent areas of East Jaintia Hills District, the authors could observe regular bat trappings by locally improvised techniques in many of the accessible caves. Enquiry with the hunters revealed that a skilled person can easily catch 50–60 bats in one night and the numbers sometimes going over 100 per night. Because of comparatively low rate of fecundity in bats, such overharvesting is certainly not sustainable. Larger species like Hipposideros lankadiva, H. armiger, etc. are preferred catch although smaller and even smelly species like Miniopterus magnater are also consumed. While most of these harvesting are for personal consumption, bat meat reportedly fetch over Rs. 500 per kg in the local market. Knowledgeable sources reported overharvesting and noticeable decline in bat population over the years especially in the well-known bat caves like Krem Labit at Shnongrim in East Jaintia Hills. Bat colonies have reportedly retreated to inaccessible cliffs and caverns in recent times which can be attributed to the severe hunting pressure.

15.3.3 Karst System of Meghalaya as a Priority Area for Bat Conservation

The Shillong Plateau is one of the most tectonically active and wet regions of the world and hosts the richest type of karst phenomena in India (Prokop 2014). Because of high elevation and heavy precipitation, these karstic regions exhibit extensive underground network of caves and drainage channels. They provide unlimited roosting opportunities for a large number of bat species. In karstic regions, most species of bats rely completely on caves as roosting sites (Rodriguez-Duran 1998). Bats are known from most of the caves in Meghalaya (Harris et al. 2008), and some caves harbour dense bat colonies containing thousands of individuals and also a number of poorly known species (Ruedi et al. 2012b, 2014). A majority of bat species in Meghalaya are known to roost in caves and therefore are dependent on caves for survival (Table 15.2). Although locally abundant, a few of these cave-dwelling species like Otomops wroughtoni, Ia io, etc. are rare or unknown in other parts of the Indian subcontinent (Bates and Harrison 1997) and deserve priority conservation attention. Disturbance and destruction of day roost sites is a major factor in bat population declines (Kunz 1982). Thus, protection of these underground roosting sites constitutes a key conservation strategy for bat fauna of the state. Unfortunately, most of the known caves and their resources in Meghalaya are in peril by unregulated mining activities and other forms of human pressure. In the absence of any legal framework for protection of bats and also their habitat, conservation of the bat fauna presents considerable challenges. The priority lies in detailed documentation of the bat caves and assessment of various forms of pressure on them. Based on these inputs, a scientific cave management plan involving the local communities can be evolved. Sustained efforts on the part of conservation organizations and the scientific communities can make a significant difference. It is high time for everybody to appreciate the gravity of the situation and do whatever it takes to protect this priceless natural heritage.

Table 15.2 Cave roosting bat species of Meghalaya
Full size table