Indian Flying Fox: Roost Ecology in Goalpara, Assam
Abstract
The present study was conducted at Krishnai Forest Range Office Campus (26°2′ 0″ North, 90°40′ 0″ East) situated at Goalpara district of Assam. Throughout the pre-monsoon season (March–May 2022), the survey location was periodically visited. The current study aims to identify the numerous roosting trees used by Indian flying foxes (P. medius), their diurnal behavioral pattern, and to assess the population size of the species together with their morphometric variations. A large mean colony size (5479 332.99) of P. medius bats was found in the study site, residing in a number of preferred roosting trees (n = 101). In April 2022, a population count of 5509 bats was recorded as the mean population size. However, the population count varies in March (5871) and May (5057). Population fluctuation was mainly due to inter-colony migration and other environmental factors. A very high population density of 4094.91 was recorded. Direct roost count method was used to estimate the population size following standard literature key (Bates and Harrison, 1997). Different times of the day were used to record the diurnal roosting habit patterns of the bats. The most frequent behavior was sleeping, which was followed by grooming, wing flapping, and wing spreading. Two of the few captured bats (n) were used to analyze the morphometric variances. The average body weight of the specimens that were caught was 699 ± 26.87g, and the average forearm length was 172.05 ± 2.616g. When compared to the caught (P. medius) bat species, the mean value of the morphometric measurements revealed a substantial variation. Roosting site selection depends on their abundance, risk of predation, availability and distribution of food resources and physical environment. An essential species for maintaining the ecosystem’s equilibrium is the Indian flying fox. For the reforestation of the forest environment, it is regarded as a crucial method of seed dissemination and pollination. The study site was selected based on the very fact that earlier no prior study was carried out in this roosting site and proved to be a significant area sustaining bats for more than 30 years with approximately 80–85 % of the species (P. medius) roosts as year round.
Introduction
Bats are the unique group of sustained-flight mammals like birds belonging to the order Chiroptera (Adhikari et al., 2010). Chiroptera (bats) account for one-fifth of mammalian species and are the second largest among 26 mammalian orders (Suga, 2009; Srinivasulu et al., 2010). Traditionally, the order Chiroptera is divided into two distinct suborders Megachiroptera are Old World flying foxes distributed within a family of 01 and the Microchiroptera includes laryngeal echolocating bats and are distributed around 18 families (Mickleburgh et al., 1992; Koopman, 1993; Hutson et al., 2001, Simmons, 2005; Srinivasulu et al., 2010, Saikia, 2019). However, using molecular and phylogenetic methods, scientists have proposed a new subdivision of Chiroptera, namely Yinpterochiroptera, which includes the megabat family Pteropodidae along with the Microbat families Rhinolophidae, Rhinopomatidae, and Megadermatidae, and Yangochiroptera including the remaining Microbat families (Teeling et al., 2002). Bats are distributed worldwide and are more ecologically diverse than any other group of mammals (Handley et al., 1996). They are widespread and have been recorded worldwide, with the exception of Antarctica and some oceanic islands (Mickleburgh et al., 2002). More than 1,400 bat species are known worldwide, 190 species belong to the suborder Megachiroptera, which is distributed within a single family Pteropodidae (Bat Conservation International 2021; Talmale et al., 2018).
There are 14 species of Pteropodidae in India and members of this family are colloquially known as flying foxes (Saikia et al., 2018). The Indian fruit bat (Pteropus medius) is a species of fruit bat in the Pteropodidae family. The Indian flying fox is known locally as Pholkhowa Borbaduli (Frugivorous; large bat) in Assamese. Pteropus medius is a social species living in a large daytime roost and is one of the largest flying fox species of the subcontinent stretching from Bangladesh, China, India, Nepal, Pakistan to Sri Lanka (Khatun, 2014). Most fruit bats studied are moderately or strongly colonial (Rainey et al., 1992). Perhaps some of them form colonies comprising a few hundred to millions of individuals (Nowak, 1999).
Their good sense of smell and sight locate sources of ripe fruit. Flowering plants are a good and preferred food source and all fruit bat species feed only on nectar, flowers, pollen and fruit, which explains their limited tropical distribution. It is considered to be an essential means of seed dispersal and pollination for reforestation of the forest ecosystem (Ali, 2010).
Indian flying fox is one of the beneficial members of the animal community that acts as a key species to keep the ecosystem in balance. Despite their high utilitarian role, these bats are mistreated in India and are highly vulnerable to environmental nuisance. Many resting populations of the species have declined sharply in response to anthropogenic activity.
They are increasingly threatened locally by the hunt for meat and medicine, the felling of roosting trees for road construction and other development purposes have hit the Indian fruit bat population acutely (Bhandarkar et al., 2018).
There is no official protection for Indian fruit bats or the other two species of fruit bats in India and indeed the Government of India’s Wildlife Protection Act 1972 included them all in the schedule IV- Vermin (ENVIS, 2022). The species requires appropriate conservation measures to protect and continue its ecological role in restoring forests.
Although Northeast India has a rich diversity of bats, this mammalian species has been studied very little in the region. The north-eastern region of India has an exceptional wealth of mammals, including over 70 bat species, some of which have only recently been described or reported (Bates & Harrison 1997; Thong et al., 2018). In Assam, there is very little published material on the Indian flying fox or the bat community as a whole (Sharma et al., 2020).
A monograph by Bates & Harrison (1997) listed 28 bat species from Assam. The state’s bat diversity is apparently not very high, comprising about 30 recorded species (Ali, 2022). A very limited information regarding the status of bat diversity in the 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 et al., 2020, Saikia et al., 2022; Ali, 2022). Considering the lack of comprehensive surveys and field studies documenting the diversity, distribution and status of the state’s bat fauna, the reported species richness in the region would undoubtedly be an underestimate (Saikia et al., 2018). This study was an initial effort in the area, a newly located roosting site, with the goal of identifying the various roosting trees used by Indian flying foxes (P. medius), their diurnal behavioural pattern, and to estimate the population size as well as their morphometric variations.
