Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 October 2021 | 13(12): 19675–19688
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.7468.13.12.19675-19688
#7468 | Received 24 May 2021 | Final received
13 August 2021 | Finally accepted 12 September 2021
Roosting habits and habitats of
the Indian Flying Fox Pteropus medius Temminck, 1825 in the
northern districts of Tamil Nadu, India
M. Pandian 1 & S.
Suresh 2
1 No. F1901, Taisha, Natesan Nagar West, Virugambakkam,
Chennai, Tamil Nadu 600092, India.
2 Department of Statistics,
University of Madras, Chepauk, Chennai, Tamil Nadu
600005, India.
1 pandian.m14@gmail.com
(corresponding author), 2 sureshstat22@gmail.com
Editor: C. Srinivasulu,
Osmania University, Hyderabad, India. Date of
publication: 26 October 2021 (online & print)
Citation: Pandian, M. & S. Suresh (2021). Roosting habits and habitats of
the Indian Flying Fox Pteropus medius Temminck, 1825 in the
northern districts of Tamil Nadu, India. Journal of Threatened Taxa 13(12): 19675–19688. https://doi.org/10.11609/jott.7468.13.12.19675-19688
Copyright: © Pandian & Suresh 2021. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: None.
Competing interests: The authors
declare no competing interests.
Author details: M. Pandian has completed MSc, PhD, in
Botany and BLIS from University of Madras and Bachelor of Education (BEd) from Annamalai University, Chidambaram and now serves
in Tamil Nadu Police Department. His area of interest is ecology and nesting
biology of birds and has published a few papers on house sparrows, weaver
birds, munias and ring-necked parakeets.
S. Suresh has completed
MSc, and PhD, in Manonmaniam Sundaranar
University, Tirunelveli and a recipient of INSPIRE Fellow under Department of
Science and Technology. He has published few articles in the field of time
series analysis and data mining in reputed journals. He is a life member of
statistics forums IISA and ISPS. He has rich knowledge in R programming
languages.
Author contributions: MP has conceptualized, designed
the research, performed survey, wrote paper, reviewed and edited the paper for
final approval. SS has analysed the data and gave
interpretations.
Acknowledgements: We thank D. Balaji (Villupuram
district), Minnal A. Giridharan,
Chitteri S. Prabakaran,
Teacher (Ranipet district) and Minnal
T. Selvapandian (Mumbai) for assisting in the survey
by data collection, data analysis and taking photographs/ videography of bats
in the field.
Abstract: This paper pertains to the study
on roosting habits and habitats of the Indian Flying Fox Pteropus
medius Temminck, 1825
in 12 villages of four northern districts—Vellore, Krishnagiri,
Tiruvannamalai, and Viluppuram—of Tamil Nadu. Studies
targeted roosting tree species, population status, diurnal-roosting behaviour,
interactions with other animals, and probable threats to the species. A total
of 22,365 individuals of the species were observed in 72 roosting
colonies in 72 trees belonging to nine families, 11 genera, and 13 species. The
tree species that harbored the greatest population of
P. medius (n= 12,465) were those of Tamarindus indica L.
(Fabaceae) (n= 39), followed by Ficus religiosa L. (Moraceae) (n=
3,960), Madhuca latifolia
J.F. Macbr. (Sapotaceae)
(n= 2,760), and Ficus benghalensis
L. (Moraceae) (n= 1,620). One-Way ANOVA revealed that
a significant relationship exists between
colony size and tree diameter at breast height (dbh),
and their canopy size (p <0.05). However, no significant difference occurred
between the colony size and tree height. The time taken for emergence of
individuals of the colony from the canopy for foraging varied between 20 and 40
min after 1750 h in the evening. The species mostly roosted on trees proximal
to human settlements, electrical power lines, and water bodies. Individuals of P.
medius used various tree species in different
areas in different geographical regions and did not maintain any consistency in
roosting tree species selection. A majority of individuals (88.7 %; n= 887)
were found roosting using both legs and a minority of P. medius
(11.3 %; n= 113) were clinging to tree branches using one. Individuals of P.
medius flew to nearby water bodies to quench
thirst and cool their bodies. Mating was observed during day roost in 146 pairs
including male-female fellatio in seven pairs. Smoke from shrines in sacred
groves, pruning of branches for various cultural reasons, populations of House
Crow Corvus splendens
(Vieillot, 1817) (Corvidae),
Black-winged Kite Elanus caeruleus
(Desfontaines, 1789) and Black Kite Milvus migrans (Boddaert, 1783)
(both Accipitridae) were key disturbances to roosting
populations of P. medius.
Keywords: Diurnal behaviours fellatio,
mating, Pteropus giganteus,
roosting trees, threats.
INTRODUCTION
The order Chiroptera
consists of over 1,400 species of bats worldwide, of which 148 species occur in
southern Asia (Simmons & Cirranello 2020; Srinivasulu et al. 2021a). Pteropodidae,
the Old-World fruit-eating bats, are well adapted to live in the tropics,
particularly in India, Bangladesh, Bhutan, Nepal, China, the Maldives, Myanmar,
Pakistan, and Sri Lanka (Helgen et al. 2009; Jnawali et al. 2011). India harbors
12 species of fruit bats and among them three occur commonly; they include Pteropus medius, P.
leschenaultii, and Cynopterus
sphinx (Srinivasulu et al. 2021b). The Indian
Flying Fox Pteropus medius
Temminck, 1825 (earlier treated as P. giganteus) is one of the largest bats and is widely
distributed in southern and south eastern Asia (Marimuthu
1996). This species is a gregarious, colonial mammal that roosts in large trees
that possibly protect them from strong winds and offer an easy updrift access
for flight. The number of individuals of P. medius
per colony was found to be varied. Between 260 and 1,550 individuals were
recorded during different months (January–October) in a single colony in the
Kathmandu valley, Nepal (Manandhar et al. 2018),
whereas a colony of 2,844 individuals was recorded in the Lower Dir district,
Pakistan (Khan et al. 2021). A total of 11,000 individuals were counted on 182
trees in Jambughoda Wildlife Sanctuary, Gujarat (Vyas
& Upadhyay 2014). An average of 43 to 6,141 individuals was counted in the
colonies on 19 tree species in Odisha (Rao & Poyyamoli
2017). In Tamil Nadu, over 600 individuals in Nallur
near Chennai (Smith 1998), 16,000 individuals in Srivaikundam
(Sudhakaran et al. 2010), and 431 individuals in Pudukottai district were enumerated. They usually prefer to
roost on tall trees in urban areas of Lahore, Pakistan (Gulraiz
2014). In Tamil Nadu, they preferred Terminalia
arjuna trees in Srivaikundam (Sudhakaran
et al. 2010) whereas Vachellia leucophloea (= Acacia leucophloea)
and Pongamia pinnata
in Pudukottai district (Tangavelou
et al. 2013)
Generally,
bat roosting sites are found adjacent to water bodies (Fenton & Barclay
1980; Kunz 1982; Thomas 1988). The colonies of P. medius
mostly preferred to choose trees for roosting near human settlements in India
and Nepal (Bates & Harrison 1997; Katuwal et al.
2019). They exhibit various diurnal behaviour during day roost and
belly-soaking behaviour is very common among this species during summer in
Purulia district of West Bengal probably to regulate body temperatures (Dey et al. 2015). This species utilizes rain water droplets
to quench its thirst by licking rain droplets from its patagium (Baskaran et
al. 2016). The majority of individuals cling to the branches using either both
legs or with single leg (Rao & Poyyamozhi 2017).
Mating in the day roost and fellatio behaviour in hetero-sexual pairs was
common among bats (Wilkinson 1986; Kerth et al. 2003;
Tan et al. 2009), and so in P. medius
individuals (Maruthupandian & Marimuthu
2013). The emergence time of P. medius
individuals from the roosting trees varied: early emergence occurred during
winter (1720‒1837 h) and delayed emergence during summer (1838‒1946 h) in
Mohanlal Ganj, Uttar Pradesh (Ramkumar et al. 2019).
Populations
of flying foxes are declining worldwide (Mildenstein
et al. 2005; Stier & Mildenstein 2005) due to
growing human population, destruction of habitats by felling of trees
(Chakravarthy & Yeshwanth 2008), hunting by
humans (Marimuthu 1996), shortage of their food
resources, and urbanization (Fujita & Tuttle 1991; Mickleburgh
et al. 2002). Deforestation, electrocution, expansion of highways, construction
of buildings, and hunting reduces populations of P. medius
(Molur et al. 2008; Ali 2010). A variety of birds of
prey and various reptiles including snakes and lizards prey upon bats (Pierson
& Rainey 1992). Ethnic communities usually hunt the Indian Flying Fox for
meat as they believe it to have medicinal value (Acharya 2008; Thapa 2008).
Various conservation attempts have been made for tree roosting P. medius (Katuwal et al. 2019).
The IUCN Red List of Threatened Species categorises conservation status of this
species as ‘Least Concern’ (Tsang 2020). No detailed studies were carried out
on the habits and habitats of P. medius in the
northern parts of Tamil Nadu. Hence to fill up this gap the present study was
carried out.
This study,
focussing on how habitat disturbances will affect the populations of P. medius, will contribute to future studies on the role
of habitat disturbances on species in southern India. In this study, we aimed
to document the diurnal roosting behaviour of P. medius
with special reference to trees utilized in northern Tamil Nadu. The following
objectives were targeted: (1) to assess the population status of P. medius and roosting tree species in the study area; (2) to
understand the relationship between the roosting sites of P. medius and distances from human settlements, electric
power lines, water bodies, and mobile-phone towers; (3) to document diurnal
behaviours including mating and pre-emergence patterns; (4) to know interaction
with other animals; and (5) to access the probable threats to their
populations.
MATERIALS
AND METHODS
Study Area
The study was carried out in 12
villages (listed in the legend of Figure 1) located in Krishnagiri,
Vellore, Tiruvannamalai, and Viluppuram districts of
northern Tamil Nadu (c. 17,000 km2, c. 80,40,000 human population).
Agriculture is the principal occupation of the residents. The maximum and
minimum annual temperatures in these districts are 36 oC
and 20 oC, respectively. The average
annual rainfall is 1,060 mm (www.tn.gov.in).
Methods
We selected 72 active roosting
colonies of P. medius distributed on 72 trees
belonging to 13 species in 12 villages where P. medius
populations were known to be locally present through nomadic gypsies. The
number of P. medius observed on each tree was
considered a single roost/colony. The roosting colonies and trees were surveyed
between 0600 and 1900 h from June 2020 to January 2021.
Questionnaire study: Eighty
respondents, all above 60 years old, residing adjacent to the roosting sites
were interviewed as they have information from the past, in the selected 12
villages using a questionnaire survey form (in the Tamil language). The
questionnaire form included questions on time periods of existence of the local
P. medius colonies, population trends, details
on roosting trees and tree selection, persecution and hunting of the flying
fox, and perception of the local community about the animal as a nuisance, and
the probable threats to the populations of local P. medius
colonies.
Population count: A population count of the
selected P. medius colonies was carried out
visually and by using a pair of Super Zenith field binoculars (Model No. 20 x
50 Field 3O, Jack Berg, El Paso, Texas, USA) following Barlow’s
(1999) direct roost-count method. The count was conducted fortnightly during
June‒July 2020 and the numbers were arithmetically averaged.
Behavioural study: Some behaviours of the species in
the colonies such as grooming, mating, and interactions with other animals were
also observed. Anthropogenic impacts such as smoke from cooking, hunting, and
pruning of trees chosen for roosting were observed and the level of impact was
categorized. The height was measured using Silva Clinometer (Gulraiz 2014), dbh (diameter at
breast height), canopy width and distance between roosting trees were measured
using 100 m measuring tape. The nearest human settlements, power lines, water
bodies, and mobile-phone towers were measured using a 100 m measuring tape. The
canopy width was obtained by cross method (Blozan
2006) by measuring the edge of the canopy shadow on the ground. The
pre-emergence and emergence activities were observed between 1700 and 1900 h
for 20 days in January 2021. Locations of the colonies and mobile-phone towers
were determined using a standard GPS (Garmin Etrex
20x, 2017, Garmin Corporation, Taiwan). Photographs and videography were made
using a digital camera (Nikon Coolpix P1000 Super-telephoto, Nikon).
Data Analysis
One-way analysis of variance
(ANOVA) was used to test the difference in means between the numbers of P. medius counted and the types of roosting tree species
by using Statistical Package for Social Science (SPSS version 25.0 software).
Roosting tree species having more than two individuals were considered for analysis.
Those tree species with less than two individuals were ignored. One-way ANOVA
was used to test the significance between the numbers of individuals of P. medius counted and the height, dbh,
and canopy size of roosting trees. Test of significance between the variables
was assessed at p <0.05.
RESULTS
Tree species selection for
roosting
A total of 22,365 individuals of P.
medius were counted from 72 colonies (Table 1).
The roosting sites occurred in and around 11 human settlements, 11 sites in
farmlands, and five sites near shrines within sacred groves. Out of the 12
villages, the maximum individuals that is 32.64 % (n= 7,298) occurred in Ongapadi (Vellore district) and the least 1.77 % (n= 398)
in Junjupalli (Krishnagiri
district). Among four districts, the highest population of P. medius (n= 9,268; 41.45 %) occurred at Vellore district
on 10 trees, followed by 23.68 % (n= 5,298) on 47 trees in Tiruvannamalai
district, and 20.91 % (n= 4,678) on seven trees in Krishnagiri
district. The least populations of 13.95 % (n= 3,121) were counted on eight
trees in Viluppuram district. On an average, 310
individuals of P. medius /tree existed in the
study area. (Table 1, Image 1).
Altogether, 13 species belonging
to 11 genera and nine families of 72 trees were roosted upon by P. medius. Bambusa arundinacea (L.) Voss (Poaceae),
a large, arborescent herb, was one among the 13 species. A total of 12,465
individuals (55.73 %) of P. medius lived on 49
trees of the family Fabaceae. Most of the colonies (53.9 % of their total
population, n= 12,055) were on Tamarindus indica L. (n= 39) and a minimum population (0.12%, n=
28) on a single Lannea coromandelica
(Houtt.) Merr. (Table
2).
The tree species used for
roosting, such as Delonix regia (Boj. ex Hook.) Raf., Azadirachta indicaA. Juss., Ceiba speciosa (A.St.Hil.) Ravenna, Lannea coromandelica (Houtt.) Merr., Madhuca longifolia J.F.Macbr., Syzygium cumini (L.) Skeels., and Terminalia arjuna L. were represented
only by either one or two trees which were excluded from the analysis.
Statistical testing (ANOVA) revealed a significant relationship between the
means of P. medius individuals and the tree
species chosen by P. medius for roosting (F5,56=
5.35, p <0.05).
One-way ANOVA
shows the relationship between the height, dbh, and
canopy size of the roosting trees. However, no significant relationship
occurred between the average number of P. medius
and heights of the trees (F2,69= 1.42, p >0.05). Nevertheless,
there was a significant difference between the average number of P. medius and the dbh of trees
used by P. medius for roosting (F2,69=
8.25, p <0.05). In addition, significant differences occurred between the
number of P. medius and the canopy size of
roosting trees (F2,69= 10.34, p <0.05).
Apparent preference of trees
close to human settlements
Sixty per cent of the trees used
for roosting (n= 43) and 80 % individuals of total population of P. medius (n= 17,880) occurred within 100 m radius from
human settlements. No roosting trees were located between 100 and 250 m. Only
40 % trees used for roosting (n= 29) and 20 % individuals (n= 4,485) of P. medius were found beyond 250 m (Figure 2).
Forty-three per cent of trees
used for roosting (n= 31) and 64.75 % of P. medius
(n= 14,482) occurred within a 25-m radius from electric power lines. A maximum
of 84.72 % of trees used for roosting and 92.1 % P. medius
(n= 20,600) occurred within a 100-m radius from power lines. Only 15.28 %
of trees used for roosting (n= 61) and 7.9 % of P. medius
(n= 1,765) occurred beyond 100 m. No mortality of P. medius
due to electrocution was noticed during the study period (Figure 3).
Ninety-six per cent of trees used
for roosting (n= 69) and 80.86 % of P. medius
(n= 18,085) occurred within 1,000-m radius from water bodies such as lakes,
ponds, rivers, and canals (Figure 4). Thirty-two per-cent of trees used for
roosting (n= 23) and 50.4 % P. medius individuals
(n= 11,272) occurred within a 500-m radius from mobile-phone towers and 62.5 %
trees (n= 45) and 28.62 % P. medius (n= 6,403)
were observed within a 501‒2000 m radius from mobile-phone towers. The
remaining 5.55 % trees (n= 4) and 20.97 % P. medius
(n= 4,690) occurred beyond 2001 m from mobile-phone towers (Figure 5).
Perception of local people
Of the 80 local respondents
interviewed, 87 % residents (n= 66) were concerned over the declining
populations of P. medius and the numbers of
trees used for roosting. That the residents of these villages consider roosting
populations of flying foxes important in their culture and life is notable. For
example, if they considered it a bad omen, they would have either cut those
trees that accommodate roosting populations of P. medius
or chased the roosting colonies away from the trees. However, in Junjupalli village, we observed that soon after a marriage
ceremony, the married couple worshipped the tree (Ficus
benghalesnsis) supporting a roosting population
of P. medius. Residents from the villages
reported that the numbers of P. medius had
reduced, compared to six decades ago. Thirty-five residents (44 %) indicated
either occasional or clandestine hunting of P. medius
for folk-medicinal reasons. Seventy-four residents (92 %) considered the
presence of a roosting colony as a sign of prosperity to their village. Sixty
residents (75 %) indicated that cracker bursting was always done only after
sunset when P. medius population was away from
the trees for foraging. To protect roosting colonies of P. medius residents of Ongapadi village
avoided bursting crackers during festive times. Seventy-four residents (92 %)
considered P. medius populations within the
village were never a nuisance; despite the fact that these animals desecrate
houses, walls, and other common public areas under the roosting trees, and the
foul odour emanating from the droppings. Sacredness and an environmental value
addition because of culture, offer ‘protection’ to populations of P. medius contributing to their conservation.
Behaviour of P. medius
During the north-east monsoon
rains (October—November 2020), individuals of P. medius
were observed clinging to tree branches with their heads and ventral parts of
their body wrapped with their membranous wings. Immediately after the rain,
they flap their wings speedily and move from one branch to another. After the
rain, they groom, scratch, and lick water droplets from their body (Image 2).
During hot summer days
(June—July), individuals of P. medius moved
from the top of the canopy downwards, i.e., midparts of the tree and roosted on
large tree trunks, probably to avoid direct exposure to sunlight. In June‒July
2020 in Marudhadu village, five incidents of P. medius individuals flying to a nearby lake and soaking
the ventral part of their body were observed.
Mating
One-hundred-and-forty-six
incidents of mating were observed in the studied villages between 0700 h and
1645 h during October—December 2020. A maximum of 26 pairs engaged in courtship
and copulation was observed in Kesavapuram village,
and two mating pairs in Anumandhai village. Before
copulation, seven incidents of males licking the genitalia of the females were
observed, which occurred for 2—4.5 min. After copulation, both pairs moved away
from each other and female‒male fellatio stopped. Two instances of males
licking their own penises before copulation were observed in Padhiri village (Table 3; Image 3).
Emergence from trees
A total of 20 pre-emergence and
emergence activities were observed for 20 days continuously from 1700 to 1900 h
in Kazhuperumbakkam and Maruvur
(Viluppuram district). Frequent and irregular
migrations of individuals from one branch to another either in the same tree or
between different trees occurred between 1710 and 1750 h. From a minimum of one
to a maximum of 11 were found flying, encircling the canopy for a few minutes
and returning to the tree used for roosting. Wing flapping and grooming
activities were high and almost all individuals of P. medius
concurrently made vocal communications, resulting in a loud, collective noise
around the roost. The emergence of the first batch of individuals (10‒50) from
the colony occurred between 1750 and 1810 h. The emergence time of the last
batch of the colony was between 1820 and 1840 h. The time taken for emergence
of individuals (80‒100) of the colony from the canopy varied between 20 and 40
min.
Interactions with other animals
Twelve incidents of Macaca radiata (E. Geoffroy, 1812) (Cercopithecidae) living on T. indica
trees in Gudiyatham and Rayandapuramwere
observed. When a troop of M. radiata climbed over T. indica trees to feed on flowers and raw fruits, P. medius individuals from the nearby branches flew away
from these trees to nearby trees. In one instance, one M. radiata was
found slapping a roosting P. medius when the
latter hindered it while plucking fruits of T. indica.
Corvus splendens
frequently visited the trees used by P. medius
for roosting, disturbing them. When the P. medius
started to fly, C. splendens selectively
chased the juveniles of P. medius away. A
total of 36 incidents of C. splendens chasing P.
medius individuals from roosting colonies were
observed. But no incidents of C. splendens
predating on the juveniles of P. medius were
found during the study (Fig 10).
Threats
Smoke disturbance to roosting
colonies of P. medius was common around
shrines located within sacred groves. Local residents cook porridge on firewood
stoves to offer to deities in the sacred groves in Marudhadu,
Kazhuperumpakkam, Padhiri, Maruvur, and Chenur during
July‒August and January‒February. The emerging smoke disturbed P. medius individuals, driving them away from the trees to
migrate to other trees (e.g., T. indica and F.
religiosa) situated outside the villages for
roosting.
Trees chosen for roosting by P.
medius adjacent to residential areas and farm
lands are frequently pruned because the village administrators see them as
obstructions to electric power lines and villagers who see them preventing
sunlight to crop plants. One P. medius
individual was noticed with a damage on its patagium. Although the exact cause
for the damage was unknown. One Black-winged Kite Elanus
caeruleus (Desfontaines,
1789) was seen hovering and roosting on power lines in the vicinity of trees
used by P. medius for day roost at Maruvur village, although no incident of attack by E. caeruleus on P. medius
was observed. Villagers remarked that Black Kites, Black-winged Kites, and
House Crows occasionally predate on the juveniles of P. medius.
DISCUSSION
Tree species selection for
roosting
The Indian Flying Fox has been
known to use nine tree species in avenues in Delhi (Mishra 2010) and 18 tree
species in Uttar Pradesh (Kumar et al. 2017). In the present study conducted in
Vellore, Krishnagiri, Tiruvannamalai, and Viluppuram districts in northern Tamil Nadu, P. medius populations used 13 tree species belonging to
nine families and 11 genera for roosting. Among the 13 species of roosting
trees, T. indica and L. coromandelica
are the most preferred by the flying fox in Tamil Nadu. The same taxa also
commonly occur in Vellore, Krishnagiri,
Tiruvannamalai, and Viluppuram districts, except H.
brasiliensis (Vijayasankar
et al. 2012) but these tree species were not selected by P. medius populations for roosting. Tree species such as P.
longifolia, Neolamarckia
cadamba (Roxb.) Bosser. (Rubiaceae), Eucalyptus
citriodora (Hook.) K.D.Hill
& L.A.S. Johnson (Myrtaceae), Mimusops
elengi L. (Sapotaceae),
Samaneae saman
(Jacq.) Merr. (Fabaceae), Tectona
grandis L.f. (Lamiaceae), Peltophorum
pterocarpum (DC.) K.Heyne,
and Lagerstroemia speciosa (L.) Pers. (Lythraceae) (Rao & Poyyamoli
2017) were not used by P. medius in Vellore, Krishnagiri, Tiruvannamalai, and Viluppuram
disricts. In Pudukkottai district, central Tamil
Nadu, P. pinnata and V. leucophloea,
especially in the sacred groves, were the trees used maximally for roosting (Tangavelou et al. 2013). In the present study, P. pinnata was the tree that housed maximum roosting
populations of P. medius (n= 71). Different
species of Eucalyptus (Myratceae) were the
most used trees for roosting in Kathmandu (Nepal) (Manandhar
et al. 2018). But in the present study area no Eucalyptus tree species
was used by P. medius for roosting, although
various species of Eucalyptus occur abundantly in the studied districts.
The reason may be due to the felling of Eucalyptus trees periodically by
the social forestry department because these trees were not allowed grow for
long periods and hence, P. medius might have
avoided selecting this tree species. These findings indicate that P. medius use various tree species in different
geographical regions and do not maintain any consistency in tree selection for
roosting.
No positive relationship occurred
between the numbers of P. medius and heights
of the trees used for roosting (F2,69= 1.42, p >0.05).
Significant relationship existed between the dbh and
canopy size of trees selected for roosting and the number of P. medius individuals in urban and semi-urban areas in
Uttar Pradesh (Kumar & Elangovan 2019). In the
present study, a significant, positive relationship occurred between the means
of P. medius individuals and numbers of A. lebbeck, P. pinnata, T.
indica, B. arundinacea,
F. benghalensis, and F. religiosa
chosen by P. medius for roosting (F5,56=
5.35, p <0.05). There was a significant difference between the average
number of P. medius and the dbh (F2,69= 8.25, p <0.05) and the canopy
size of trees used by P. medius for roosting
(F2,69= 10.34, p <0.05). It indicates that individuals of P. medius preferred trees with larger dbh
and larger canopy size for roosting in the study area.
Apparent preference of trees
close to human dwellings
In the Indian
subcontinent, populations of P. medius mostly
preferred to choose trees for roosting near human settlements (Bates &
Harrison 1997). In lower Nepal, most of the colonies of P. medius were recorded close to human settlements and in
farmlands (Katuwal et al. 2019). This species roosts
on trees that occur close to human settlements in Tirunelveli district, viz.,
sacred groves, and agricultural lands (Jayapraba
2016). In the present study, 60 % of trees (n= 43) chosen for roosting and 80 %
P. medius individuals (n= 17,880) were found
within 100 m radius from human settlements and hence it is in accordance with
the observations of Bates & Harrison (1997), and Katuwal
et al. (2019).
Behaviours observed
In New South Wales, Australia,
flying foxes were observed to visit nearby water bodies in peak summers
to soak their fur and wings to cool their bodies (Welbergen
et al. 2008). Belly-soaking behaviour is very common among the Indian Flying
Fox during summer in Purulia district of West Bengal (Dey
et al. 2015). In the present study, the observations of partial dipping of its
ventral body surfaces in water might have been to quench its thirst and to
reduce its body temperatures during hot summer and hence it matches with the
views of Dey et al. (2015) and Welbergen
et al. (2008).
Populations of P. medius usually roost on trees for 12‒14 h daily hanging
from branches. A majority of individuals (88.7 %) were found roosting using
both legs and a minority of P. medius (11.3 %)
were clinging to tree branches using one. They probably relax their leg muscles
by alternately using both or a single leg and it requires further studies. The
majority of individuals clinging to the branches used both legs during day
roost as stated by Rao & Poyyamozhi (2017).
After rainfall the individuals of
P. medius, groom, scratch, and lick their body
to remove the water droplets (Maruthapandian & Marimuthu 2013). This species utilizes rain water droplets
to quench their thirst by licking rain droplets from the wing membrane
(Baskaran et al. 2016). As stated by the above authors, in the present study
also we observed similar behaviours of P. medius
individuals scratching and licking its body and removing water droplets. The
droppings of P. medius desecrate human
residences, common usage areas, and cause foul odour, but the residents
tolerate it and allow roosting colonies on trees in their villages.
The occurrence of mating in the
day roost and fellatio behaviour in hetero-sexual pairs was common among P. medius individuals (Wilkinson 1986; Kerth
et al. 2003; Maruthupandian & Marimuthu
2013; Tan et al. 2009). Similar behaviours while mating during day and
female-male fellatio were observed in the current study as stated by the above
authors.
Emergence from trees
The emergence time of P. medius individuals from the trees varied: early
emergence occurred during winter (1720‒1837 h) and delayed emergence during
summer (1838‒1946 h) in Mohanlal Ganj, Uttar Pradesh (Ramkumar et al. 2019). In
the present study the emergence period during the winter season was between
1750‒1840 h and it nearly corroborates with the observations of Ramkumar et al.
(2019). The time taken for emergence of all the individuals of the colony was
found to vary: 21 min to 39 min. The variations of emergence time during summer
have not been studied.
Interactions with other animals
A variety of birds of prey, both Falconiformes and Strigiformes,
various reptiles including snakes and lizards prey upon them (Pierson &
Rainey 1992). Though monkeys and house crows caused disturbance to P. medius individuals, no incidents of predation was
reported in the present study area. Villagers remarked that individuals of
Black Kites and Black-winged Kites had frequented roosting colonies and predate
of juveniles of P. medius and hence it
corroborates with the findings of and Pierson & Rainey (1992). However, no
predation by Black Kites, Black-winged Kites, and reptiles were noticed in the
study sites.
Threats
This species
roost on trees that occur close to human settlements, farmlands and sacred
groves. Because of human habitation, electrical power lines usually occur close
to those roosting trees. Ali (2010) reported small numbers of P. medius were found electrocuted and died in Dhubri district, Assam. The present survey revealed that no
mortality of P. medius individuals was found
in the surveyed four districts. Although 84.72 % trees chosen for roosting and
92.1 % P. medius individuals (n= 20,600)
occurred within a 100-m radius from electrical power lines, no mortality due to
electrocution was observed.
Hunting of bats for meat is still
prevalent in some parts of Nepal (Katuwal et al.
2019). The meat of flying foxes (‘valguli mamsa’ in local language) is believed to be of some
therapeutic value and its consumption is recommended locally. Meat of this
species is consumed for treating rheumatism in India (Nowak 1999) and the
people of Attapadi region (Kerala) believe that the
meat of P. medius treats asthma and chest pain
(Padmanaban & Sujana
2008). During the survey, 44 % of residents (n= 35) indicated either occasional
or clandestine hunting of P. medius for
folk-medicinal reasons.
Electromagnetic
radiations exert an abnormal behaviour and affect the foraging activities of
bats in Aberdeen, Scotland. Their activity was more rigorous in the control
sites than the sites exposed to a high level (>2v/m) of electromagnetic
radiation (Nicholls & Racey 2007). In Mumbai, the
number of flying foxes was found to have decreased when mobile-phone towers
occurred within 80 m from a roosting colony (Kumar 2010). In the present study
the minimum distance between a tree used for roosting and a mobile-phone tower
was 40 m at Ongapadi (Vellore district) and the
maximum 6,000 m in Maruvur
(Viluppuram district). The trees used for roosting
and P. medius populations revealed that a
large number of trees chosen for roosting (31.94 %; n= 23) and P. medius individuals (50.4 %; n= 11,272) occurred within
500 m radius from the mobile-phone towers. However, in the event of the
existence of mobile-phone towers in almost all villages, the situation of a
tree 40 m distance from the mobile-phone tower, the exact impact of the
mobile-phone tower on the roosting colonies of P. medius
needs further study.
CONCLUSION
The populations of P. medius used 13 tree species belonging to 11 genera and
nine families for roosting at various habitats, such as human dwellings, farmlands,
and water bodies. No positive relationship occurred between the numbers of P.
medius and heights of the trees used for
roosting. There was a significant difference between the average number of P.
medius and the dbh and
the canopy size of trees used by P. medius for
roosting. The individuals of P. medius were
found soaking themselves in water during summer probably to reduce body
temperatures. While roosting, they mostly cling on to tree branches using both
legs, rarely using one. Mating and fellatio behaviour in hetero-sexual pairs
were observed during the day roost. The time taken for emergence of individuals
of the colony from the canopy varied between 20 and 40 min. No mortality due to
electrocution was observed. The impact of mobile-phone towers on roosting
colony needs further study. The roosting populations were disturbed by
individuals of Bonnet Macaque, House Crow, Black Kite, and Black-winged Kite.
Anthropogenic impacts like hunting, pruning trees used for roosting and smokes
emanated from sacred groves during festivals
pose a threat to the populations of P. medius.
In spite of rapid urbanization,
industrialization, population increase, habitat destruction, hunting by
villagers and decreasing areas of cultivation including orchards, considerable P.
medius populations exist in the study area. A special management plan could be devised
for the area, considering the anthropogenic and natural stresses to which the
habitat is currently subjected. The present roosting sites should be declared
as protected areas and further organisations (NGOs) have to play a major role
in creating awareness among the general public to protect this species. This
study clearly demonstrates the presence of 22,365 Indian Flying Fox individuals
in their natural habitats and identifies current and emerging challenges in
conservation of habitats of such key species in the natural ecosystems.
Table 1. District-wise details of
villages, GPS co-ordinates, number of roosting trees and total number of Pteropus medius counted in the
study area.
|
District |
Name of the village |
GPS |
Total no. of trees have
roosting colony |
Total no. of P. medius counted on these trees |
Percentage (%) of P. medius |
1 |
Vellore |
Gudiyatham |
12.938438oN,
78.861062oE |
4 |
1970 |
8.8 |
2 |
Ongapadi |
12.822734oN,
78.946628oE |
6 |
7298 |
32.63 |
|
3 |
Krishnagiri |
Junjupalli |
12.564656oN,
78.164119oE |
4 |
398 |
1.64 |
4 |
Chenur |
12.360311oN,
78.583989oE |
3 |
4280 |
19.13 |
|
5 |
Tiruvannamalai |
Rayandapuram |
12.092188oN,
78.928710oE |
13 |
2723 |
12.17 |
6 |
Kesavapuram |
12.655683oN,
79.126282oE |
18 |
1417 |
6.33 |
|
7 |
Vandavasi |
12.510984oN,
79.597503oE |
10 |
700 |
3.12 |
|
8 |
Marudhadu |
12.490742oN,
79.653357oE |
6 |
458 |
2.94 |
|
9 |
Viluppuram |
Kazhuperumpakkam |
12.067317oN,
79.829502oE |
1 |
780 |
3.48 |
10 |
Anumandhai |
12.131800oN,
79.911418oE |
4 |
1251 |
5.59 |
|
11 |
Maruvur |
12.164664oN,
79.515650oE |
1 |
410 |
1.83 |
|
12 |
Padhiri |
12.314802oN,
79.755639oE |
2 |
680 |
3.04 |
|
Total |
4 |
12 |
|
72 |
22365 |
100 |
Table 2. Details on the diversity
of roosting trees and total Pteropus medius counted in the study area.
|
Type of roosting
trees |
Family |
Total no. of trees have P. medius roosting |
Total no. of P. medius individuals counted |
1 |
Albizia lebbeck (L.) Benth. |
Fabaceae |
5 |
219 |
2 |
Dellonix regia (Boj. ex Hook.) Raf. |
Fabaceae |
1 |
120 |
3 |
Pongamia pinnata (L.) Panigrahi |
Fabaceae |
4 |
71 |
4 |
Tamarindus indica L. |
Fabaceae |
39 |
12055 |
5 |
Azadirachta indica A.Juss. |
Meliaceae |
1 |
46 |
6 |
Bambusa arundinacea (L.) Voss |
Poaceae |
7 |
468 |
7 |
Ceiba speciosa (A.St.Hil.) Ravenna |
Malvaceae |
2 |
175 |
8 |
Ficus benghalensis L. |
Moraceae |
4 |
1620 |
9 |
Ficus religiosa L. |
Moraceae |
3 |
3960 |
10 |
Lannea coromandelica (Houtt.)
Merr. |
Anacardiaceae |
1 |
28 |
11 |
Madhuca longifolia J.F.Macbr. |
Sapotaceae |
1 |
2760 |
12 |
Syzygium cumini (L.) Skeels. |
Myrtaceae |
2 |
56 |
13 |
Terminalia arjuna (Roxb.) Wight & Arn. |
Combretaceae |
2 |
787 |
Total |
9 |
72 |
22365 |
Table 3. Details of mating pairs
and female-male fellatio observed during day roost in October and December 2020
in the study area.
|
District |
Name of the village |
Total no. of mating individuals
observed |
Female-male fellatio observed |
1 |
Vellore |
Gudiyatham |
12 |
2 |
2 |
Ongapadi |
08 |
0 |
|
3 |
Krishnagiri |
Junjupalli |
14 |
0 |
4 |
Chenur |
04 |
1 |
|
5 |
Tiruvannamalai |
Rayandapuram |
22 |
0 |
6 |
Kesavapuram |
26 |
2 |
|
7 |
Vandavasi |
08 |
0 |
|
8 |
Marudhadu |
14 |
0 |
|
9 |
Viluppuram |
Kazhuperumpakkam |
20 |
1 |
10 |
Anumandhai |
02 |
0 |
|
11 |
Maruvur |
06 |
0 |
|
12 |
Padhiri |
12 |
1 |
|
Total |
4 |
12 |
146 |
7 |
For figures
& images - - click here
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