Cryptic Rhinolophus pusillus Temminck , 1834 ( Chiroptera , Rhinolophidae ) : a new distribution record from the Chittagong Hill Tracts , Bangladesh

Rhinolophus pusillus is a common species of India and Nepal in South Asia. Here, we report a new record of this bat captured in the mixed evergreen forest in Rangamati, southeastern part of Bangladesh. The identification was based on external morphology along with cranio-dental measurements. Roost counts was conducted through direct observation.


Introduction
The Least Horseshoe Bat, Rhinolophus pusillus Temminck, 1834 is native to Southeast Asia and can be found in Myanmar, Thailand, Laos, Vietnam, Cambodia, Peninsular Malaysia, Borneo and also including India, South China to Indonesia (Francis 2008, Hutson et al. 2008).Like other horseshoe bats, it naturally resides in caves, clumps of bamboo, or more seldom in houses (Hutson et al. 2008), but recent study suggests that this species is more suited to evergreen forests (Soisook et al. 2016).Although R. pusillus is widely distributed on the eastern part of Asia, little information is available from the southern part of its range, with just a few records from India and Nepal (Bates andHarrison 1997, Molur et al. 2002).
The Chittagong Hill Tracts (CHT) is positioned at the southeastern part of Bangladesh and border the Indo-Burma biodiversity hotspot (Myers et al. 2000).The CHT is a mixed-evergreen forest, the last remaining habitat for several endangered species in Bangladesh (IUCN Bangladesh 2015, Khan 2015).Among these species, bats are an important part of the fauna because of the availability of caves, gorges and crevices in the hills, but unfortunately they are least studied.During a survey of bats in the CHT, a colony was detected in a small cave at Rajasthali upazila, Rangamati district (22°20.914ʹN, 092°16.676ʹE) on 6 August 2016 (Fig. 1).The cave is roughly 12.2 m long, 3.1 m high and 0.6 m wide, but the entrance was narrower.It hosted a mixed colony of up to 20 individuals of horseshoe bats and leaf-nosed bats.

Methods
Two individuals were captured with a mist net while the remainder of the bats hid inside the chamber.Standard protocol was maintained in the bat's capture (Kunz and Kurta 1988) and measurements were taken with digital NOTES ON GEOGRAPHIC DISTRIBUTION slide caliper with accuracy to the nearest 0.01 mm.Among the 2 captured bats, 1 was identified as Hipposideros larvatus (Horsfield, 1823) and the one was an unidentified adult horseshoe bat.Unable to be identified in the field, it was deposited as a voucher specimen (WLMA-0011) in the Wildlife Lab, Department of Zoology at Jahangirnagar University, Bangladesh.

Discussion
Bat diversity and abundance studies are rare in Bangladesh with only a few checklists published (Khan 2001, 2015, Sarker and Sarker 2005, Srinivasulu and Srinivasulu 2005).Recently, previous works were compiled by IUCN Bangladesh (2015); the resulting list includes 35 bat species from throughout the Bangladesh, but R. pusillus was not among the known species.The new locality of R. pusillus reported here from the southeastern Bangladesh

B A
is the first for the country and extends the range of this species by approximately 550 km south from the nearest previously known occurrence in India (Fig. 1).
Apparently, no obvious threats are known because the ethnic people residing nearby do not hunt bats for meat or medicine.The entrance of the cave is narrow, which minimizes the chance for disturbance.Further investigation is recommended on ecological aspects of R. pusillus from the study area.

Figure 1 .
Figure1.The new record of Rhinolophus pusillus from Bangladesh; the green square is the cave site from Bangladesh whereas the blue squares are the nearest records of R. pusillus reported from Meghalaya, Assam and northern Myanmar.