First record of a Wrinkle-lipped Free-tailed Bat Chaerephon plicatus Buchannan, 1800 (Mammalia: Chiroptera: Molossidae) colony in Sri Lanka, with notes on echolocation calls and taxonomy

doi: http://doi.org/10.11609/jott.3279.9.4.10115-10120 | ZooBank: urn:lsid:zoobank.org:pub:639DB651-5E25-43DB-A637-4CB539614937

Editor: Anonymity requetsed. Date of publication: 26 April 2017 (online & print)

 

Manuscript details: Ms # 3279 | Received 08 January 2017 | Final received 30 March 2017 | Finally accepted 02 April 2017

 

Citation: Kusuminda, T. & W.B. Yapa (2017). First record of a Wrinkle-lipped Free-tailed Bat Chaerephon plicatus Buchannan, 1800 (Mammalia: Chiroptera: Molossidae) colony in Sri Lanka, with notes on echolocation calls and taxonomy. Journal of Threatened Taxa 9(4): 10115–10120; http://doi.org/10.11609/jott.3279.9.4.10115-10120

 

Copyright: © Kusuminda & Yapa 2017. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use of this article in any medium, reproduction and distribution by providing adequate credit to the authors and the source of publication.

 

Funding: None.

 

Competing interests: The authors declare no competing interests.

 

Acknowledgements: We are extending thanks to Ms. Madumi Kariyawasam, Ms. Sumudu Jayakody and Mr. Malith Wijeratne of University of Colombo for giving their assistance during field works. We thank Director Generals of the Central Cultural Fund (CCF), Archeological Department of Sri Lanka and Department of Wildlife Conservation in Sri Lanka for providing their permission to work in the study site and capture bats (Permit No. WL/3/2/02/2016). We thank Mr. Kusumsiri Kodituwakku (CCF), Mr. Senaka Jayasuriya and Mr. Ranjith Bandara (Archeological Department) for their support given during field works. We acknowledge to Dr. Paul Bates, Dr. Vu Dinh Thong, Dr. Bruce Patterson, Dr. Tamás Görföl, Mr. Timothy Hornby and Mr. Duminda Dissanayake for providing necessary literature on the focal species and photographs of museum specimen to confirm the species identifications. We thank Dr. Jon Flanders for his helpful comments on the manuscript. Finally encouragements received from Mr. Bernard Geeganage, Dr. Amani Mannakkara, Mr. Sameera Suranjan Karunarathna and Mrs. Niroshi Madushani are highly appreciated.

 

 

 

 

 

Free-tailed bats of the family Molossidae are thought to be the swiftest of all bats, and their tendency to fly well above the canopy keeps them out of human reach (Freeman 1981). Members of this widely-distributed family are found in Africa, southern Europe, southern Asia, Australia and North, Central and South America (Bates & Harrison 1997). The number of species in the family continues to grow with current estimates totaling 111 species (Ammerman et al. 2012; Ralph et al. 2015; Tsang et al. 2016). Four species of free-tail bats belonging to three genera are reported from southern Asia (Bates & Harrison 1997; Srinivasulu et al. 2010). In Sri Lanka only two species of free-tail bats have been recorded: Egyptian Free-tailed Bat Tadarida aegyptiaca and the Wrinkle-lipped Free-tail Bat Chaerephon plicatus Buchannan 1800 (Phillips 1980; Bates & Harrison 1997).

C. plicatus is a geographically widespread species ranging from India and Sri Lanka to Myanmar, Thailand, Cambodia, Vietnam, southern China, Hong Kong, and southeast to Philippines, Malaysia, Lao PDR and Indonesia (Csorba et al. 2014). The current literature gives very little information on the population status and roosting ecology of this species in the Indian subcontinent (Bates & Harrison 1997). C. plicatus was first recorded in Sri Lanka in 1931 from Kumbalgamuwa in the Central Province (Phillips 1932) (Fig. 1). It was described as a subspecies, Chaerephon plicatus insularis, based on the three specimens collected by shooting free flying bats (Phillips 1932). After 65 years a single specimen was captured in a mist net in Bulathsinhala of the Western Province of Sri Lanka in 1996 (Bates & Harrison 1997) (Fig. 1). Bates & Harrison (1997) speculated that this species probably roosted in a crevice in the sheer rock face above the Pahiyangala temple. Chaerephon plicatus has therefore only been recorded twice in Sri Lanka despite several extensive field studies on Sri Lankan bats being carried out in the recent past (Digana et al. 2001; Yapa et al. 2002). At present, C. plicatus is listed as a Critically Endangered species in Sri Lanka and presumably Least Concern worldwide due to its wide distribution (Ministry of Environment 2012; Csorba et al. 2014). In this paper we report the discovery of a roosting colony of C. plicatus in Sri Lanka for the first time.

 

 

Materials and Methods

Study site

Field studies were conducted in the Sigiriya rock fortress (7057’N & 80045’E) in the Matale District near Dambulla City, Central Province, Sri Lanka in May 2016 (Fig. 1). Sigiriya rock fortress is a UNESCO World Heritage Site and one of Sri Lanka’s most well-known and popular tourist destinations, visited by thousands of people every year. The gigantic granite rock rises 200 m above the surrounding plain (377 m above sea level), which lies within the Sigiriya sanctuary and surrounded to the west by 40ha of parkland and ornamental gardens, situated in the dry zone. The study area receives a mean annual rainfall of 1,750mm with a distinct dry season from May to September. The mean annual daytime temperature is approximately 300C, although the maximum temperature may exceed 370C (Pavey et al. 2001; Perera 2012; Dissanayake et al. 2014).

 

Field sampling

There is a man-made observation platform at a feature known as the Mirror Wall at the bottom of the western rock face. A network of staircases leads from the base of the rock to this platform, from which during the initial survey on 14 December 2015 a colony of bats was recorded and observations of the roosting site were made using a 10x26 binocular (Bushnell Outdoor Products, USA). GPS coordinates were taken using a Garmin eTrex 20 hand-held GPS receiver (Garmin International, Inc., USA). Roosting bats were counted using photos of the site (Thomas & LaVal 1988; Sutherland 2006), and during a subsequent visit on 08 May 2016 a mist net was set near to the Mirror Wall in front of the entrance of the roosting site from 17:45–18:30 hr. Dimensions of the mist net were 2.5x6 m, and mesh size was 38mm. Captured bats were immediately removed from the net and kept in clean cotton bags for identification. A wing punch from the left wing of each specimen was taken using 3mm Miltex biopsy punch (Integra Lifescience Corporation, USA) after sterilizing the cutting edge. Tissue samples were stored in 99% ethanol for future molecular analysis.

Morphological measurements

Measurements of captured individuals were recorded using a digital vernier caliper (Mitutoyo, Japan): forearm length (FA), head and body length (H&B), tail length (T), tibia length (Tib), hind foot length (HF), length of third metacarpal (3mt), length of first phalange of 3mt (1ph 3mt), length of second phalange of 3mt (2ph 3mt), length of fourth metacarpal (4mt) and length of fifth metacarpal (5mt). Weights were measured using a 100g spring balance (Pesola AG, Switzerland). Photographs of bats were taken using Fujifilm finepix S4000 digital camera (Fujifilm Holding Corporation, Japan). Species identification was done using the original description of the species (Buchannan 1800) and other local and regional bat guides (Phillips 1980; Bates & Harrison 1997).

Acoustic measurement

After recording morphological and morphometric data, bats were released at the capture site and their echolocation calls were recorded during release using a Pettersson M500 microphone (Pettersson Elektronik AB, Sweden) and BatSound Touch software (Pettersson Elektronik AB, Sweden) on a Dell Core i5 laptop (Dell Inc., USA) as sound files (.wav) (Audio 1). A total of 10 individuals, unambiguous echolocation calls with high signal to noise ratio of four free flying individuals of C. plicatus were selected for further analyses. Bat echolocation calls were analysed using BatSound Pro v.3.32 (Pettersson Elektronik AB, Sweden) with software settings at FFT size = 1024 samples, with 95% overlap in a Hanning Window. From spectrograms, standard acoustic parameters of the fundamental calls were measured manually in kilohertz (kHz): Start Frequency (SF), End Frequency (EF) and Frequency with maximum Energy (FmaxE) or Peak Frequency. Call duration (t), and Inter-Pulse Interval (IPI) of selected calls were measured in milliseconds (ms) from the Oscillograms (Brigham et al. 2004; Hughes et al. 2011).

Results

Four bats were captured during evening emergence: three males and a female (weight 15–28 g). Morphometric data for these specimens were compared with published data (Tables 1 & 2). Forearm measurements obtained from this study (45.2–49.1 mm) are within the forearm measurements (43.1–50.2 mm) compared in Table 1 except for measurements published by Phillips (1932). External morphological features confirm that this species is a member of the Family Molossidae, and it can clearly be distinguished from all other bats so far recorded in Sri Lanka (Image 1A). Ears are large and irregular in shape with their anterior borders connected with a skin fold. A strip of fur is visible dorsally, just below the anterior edge of ears, starting from inner base of ear. Antitragus well developed and prominent. Tragus very small, truncated (Image 1B), and concealed entirely by the antitragus. Muzzle almost naked, but has several long, erect bristles and more short bristles, muzzle broad and blunt with very thick, fluted lips, the upper lip overhanging the lower. Eyes relatively large. Wings long (Wingspan: 30–33 cm) and narrow with the membranes arising from tibia. Interfemoral membrane poorly developed. Tail relatively shorter (47–63 %) than the head and body length, stout, naked and major portion free and protruding from the outer edge of the interfemoral membrane; Thumb small with a well-developed pad at the base. Feet rather short, the toes and their small claws are partially concealed by longish hair; outer toes relatively thickened and the spatulate hairs densely on ventral surface of the first and fifth digits. Pelage short, very dense and soft, somewhat velvet, dark brown on upper side, slightly paler on ventral surface. Another distinct feature of the captured bats is that the rump on the dorsal surface is characteristically naked (Image 1C). The dorsal fur coat never extends to the lateral margins of the wing membranes. In contrast, fur extends to the ventral surface of wing-membrane including the interfemoral membrane.

The focal colony of C. plicatus was roosting inside vertical crevices in the west face of Sigiriya Rock (Image 2). The crevice runs vertically about 3m and the width is rather narrow, not more than 10cm. The colony size appeared to be about 300 individuals. Bats were clinging on to the rock surface using their hind feet and thumbs while keeping heads downward. Loud social calls were very distinct even at a distance of 10–15 m from the roost, but as Little Swifts Apus affinis are also occupying nearby crevices of the rock surface it can be hard to detect the colonies of the bats for an inexperienced observer. Emergence occurred at 3 minutes before sunset (18:18) on 08 May 2016 with one or two individuals leaving at a time. The returning bats first landed on the vertical rock face closer to the crevice and then crawled in to the crevice forward.

Analysis of the echolocation calls of each of the four released bats (n=10 calls) were distinctly narrow band, shallower frequency modulation calls with low peak frequency (24.9–30.3 kHz) with an average call duration of 7.7ms (Table 3). For each call the spectrogram clearly shows one fundamental signal, one harmonic and a partial echo of the fundamental signal (Image 3). The calls are characterized with the presence of a distinct small hook at the beginning of the call (Image 3).

 

 

 

 

 

 

 

 

 

 

Discussion

This is the first confirmed record of a roosting site of C. plicatus in Sri Lanka, and the first report of this species on the island in almost 20 years. C. plicatus has never been captured in several island-wide surveys conducted previously (Digana et al. 2001; Yapa et al. 2002). Free-tailed bats are fast flying bats and tend to fly well above the canopy and out of human reach (Freeman 1981). They use a wide variety of roosts in caves, rock crevices, tree cavities and manmade structures (Altringham 2011). Shek (2006) reported that nothing is known about the roosting sites of this species in Hong Kong. According to Thong (2014), C. plicatus roosts in a cave of limestone karst and crevices of rocks in Vietnam. Colonies range between thousands and millions of individuals. Aye (2006) reported that the larger roosts of focal species are mainly recorded in spacious dome-shaped caves with large entrances in Myanmar. In Thailand, there are 18 known caves with large colonies of C. plicatus (Boonkird & Wanghongsa 2001). In South Asia this species is widely distributed in range but found only in a few localities within each country (Molur et al. 2002). Knowledge of a roosting site is vitally important in studying life history traits such as breeding biology, social behavior, diet, and activity patterns (Altringham 2011). It is our belief that the discovery of a natural roost of C. plicatus for the first time in Sri Lanka will pave the way for a number of future studies to understand the biology of this species and to adopt necessary conservation measures.

Echolocation calls recorded as part of this study are similar to those previously documented for this species (Borissenko & Kruskop 2003; Utthammachai 2009; Deshpande & Kelkar 2015), although there is some variation as shown in Table 3. Geographical variation is common in the echolocation calls of bat species (Altringham 2011; Chattopadhyay et al. 2012).

Measurements of the specimens captured in the present study, corresponds to the published and available measurements by Bates & Harrison (1997) in Sri Lanka and Thong (2014) in Vietnam but different from the C. p. insularis recorded by Phillips (1932) from Sri Lanka. Moreover, there are few prominent morphological differences found between original description of Chaerephon plicatus by Buchannan (1800) and original description of Chaerephon plicatus insularis by Phillips (1932), such as naked rump area and fur spreading into the wing membrane of C.plicatus: however in C. p. insularis rump area is not naked and fur not spread into the wing membrane. Hill (1961) reviewed the genus Tadarida (including Chaerephon) in Indo-Australian region but had not elaborated on these prominent variations and Sri Lankan specimens are classified as subspecies of C. plicatus (C. plicatus insularis) based on darker colour and slightly smaller size. Bates & Harrison (1997) who reviewed the taxonomy of the bats of Indian Subcontinent had also documented the Sri Lankan species as C. plicata insularis based on Hill’s (1961) classification.

It is clear that there are significant morphological variations between the specimens recorded by Phillips (1932), with the subsequent records of C. plicatus by Bates & Harrison (1997) and by us in the present study, as well as with the type specimens by Buchannan (1800). Therefore, the taxonomic status of the Chaerephon plicatus insularis described by Phillips (1932) needs to be studied in detail to resolve this taxonomic ambiguity.

 

 

Conclusion

The taxonomic status of the Chaerephon plicatus insularis described by W.W.A. Phillips in 1932 needs to be studied in detail to resolve this taxonomic ambiguity between these two specimens. The discovery of a natural roost of C. plicatus for the first time in Sri Lanka will pave the way for a number of future studies to understand the biology and taxonomy of this species.

 

 

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