Roost ecology, population size, behavioral patterns and morphometric analysis

Introduction

Bats are the unique group of sustained-flightmammals like birds belonging to the order Chiroptera(Adhikari et al., 2010). Chiroptera (bats) account forone-fifth of mammalian species and are the secondlargest among 26 mammalian orders (Suga, 2009;Srinivasulu et al., 2010). Traditionally, the orderChiroptera is divided into two distinct subordersMegachiroptera are Old World flying foxesdistributed within a family of 01 and theMicrochiroptera includes laryngeal echolocating batsand are distributed around 18 families (Mickleburghet al., 1992; Koopman, 1993; Hutson et al., 2001,Simmons, 2005; Srinivasulu et al., 2010, Saikia,2019). However, using molecular and phylogeneticmethods, scientists have proposed a new subdivisionof Chiroptera, namely Yinpterochiroptera, whichincludes the megabat family Pteropodidae along withthe Microbat families Rhinolophidae,Rhinopomatidae, and Megadermatidae, andYangochiroptera including the remaining Microbatfamilies (Teeling et al., 2002). Bats are distributedworldwide and are more ecologically diverse than anyother group of mammals (Handley et al., 1996). Theyare widespread and have been recorded worldwide,with the exception of Antarctica and some oceanicislands (Mickleburgh et al., 2002). More than 1,400bat species are known worldwide, 190 species belongto the suborder Megachiroptera, which is distributedwithin a single family Pteropodidae (Bat ConservationInternational 2021; Talmale et al., 2018). 

There are 14 species of Pteropodidae in India andmembers of this family are colloquially known asflying foxes (Saikia et al., 2018). The Indian fruit bat(Pteropus medius) is a species of fruit bat in thePteropodidae family. The Indian flying fox is knownlocally as Pholkhowa Borbaduli (Frugivorous; largebat) in Assamese. Pteropus medius is a social speciesliving in a large daytime roost and is one of the largestflying fox species of the subcontinent stretching fromBangladesh, China, India, Nepal, Pakistan to SriLanka (Khatun, 2014). Most fruit bats studied aremoderately or strongly colonial (Rainey et al., 1992).Perhaps some of them form colonies comprising a fewhundred to millions of individuals (Nowak, 1999).

Their good sense of smell and sight locate sources ofripe fruit. Flowering plants are a good and preferredfood source and all fruit bat species feed only onnectar, flowers, pollen and fruit, which explains theirlimited tropical distribution. It is considered to be anessential means of seed dispersal and pollination forreforestation of the forest ecosystem (Ali, 2010).

Indian flying fox is one of the beneficial members ofthe animal community that acts as a key species tokeep the ecosystem in balance. Despite their highutilitarian role, these bats are mistreated in India andare highly vulnerable to environmental nuisance.Many resting populations of the species have declinedsharply in response to anthropogenic activity. 

They are increasingly threatened locally by the huntfor meat and medicine, the felling of roosting trees forroad construction and other development purposeshave hit the Indian fruit bat population acutely(Bhandarkar et al., 2018).

There is no official protection for Indian fruit bats orthe other two species of fruit bats in India and indeedthe Government of India's Wildlife Protection Act1972 included them all in the schedule IV- Vermin(ENVIS, 2022). The species requires appropriateconservation measures to protect and continue itsecological role in restoring forests. 

Although Northeast India has a rich diversity of bats,this mammalian species has been studied very little inthe region. The north-eastern region of India has anexceptional wealth of mammals, including over 70 batspecies, some of which have only recently beendescribed or reported (Bates & Harrison 1997; Thonget al., 2018). In Assam, there is very little publishedmaterial on the Indian flying fox or the batcommunity as a whole (Sharma et al., 2020).

A monograph by Bates & Harrison (1997) listed 28bat species from Assam. The state's bat diversity isapparently not very high, comprising about 30recorded species (Ali, 2022). A very limitedinformation regarding the status of bat diversity inthe state has found it mentioned in (Bates & Harrison  1997; Sinha, 1999; Ali et al., 2010; Boro et al., 2013;Boro & Saikia, 2015; Rahman et al., 2017; Sharma etal., 2020, Saikia et al., 2022; Ali, 2022). Consideringthe lack of comprehensive surveys and field studiesdocumenting the diversity, distribution and status ofthe state's bat fauna, the reported species richness inthe region would undoubtedly be an underestimate(Saikia et al., 2018). This study was an initial effort inthe area, a newly located roosting site, with the goal ofidentifying the various roosting trees used by Indianflying foxes (P. medius), their diurnal behaviouralpattern, and to estimate the population size as well astheir morphometric variations.