Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 September 2020 | 12(13): 16752–16763
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
doi: https://doi.org/10.11609/jott.3034.12.13.16752-16763
#3034 | Received 28 August 2019 | Final
received 04 September 2020 | Finally accepted 11 September 2020
The Critically Endangered White-rumped Vulture Gyps bengalensis
in Sigur Plateau, Western Ghats, India: Population,
breeding ecology, and threats
Arockianathan Samson 1 & Balasundaram
Ramakrishnan 2
1 Vulture Programme, Bombay Natural
History Society, Mumbai, Maharashtra 400001, India.
2 Mammalogy and Forest Ecology Lab,
Department of Zoology and Wildlife Biology, Government Arts College,
Udhagamandalam,
The Nilgiris,
Tamil Nadu 643002, India.
1 kingvulture1786@gmail.com (corresponding
author), 2 bio.bramki@gmail.com
Editor: Chris Bowden, The Royal Society for the Protection of
Birds, Sandy, UK. Date of publication:
26 September 2020 (online & print)
Citation:
Samson, A. & B. Ramakrishnan (2020). The Critically Endangered White-rumped
Vulture Gyps bengalensis in Sigur Plateau, Western Ghats, India: Population, breeding
ecology, and threats. Journal of
Threatened Taxa 12(13): 16752–16763. https://doi.org/10.11609/jott.3034.12.13.16752-16763
Copyright: © Samson & Ramakrishnan 2020. 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: A. Samson is a research biologist
under the Vulture Programme at Bombay Natural History
Society, Mumbai, India. He submitted his PhD on “Studies on Population,
Breeding Ecology and Conservation Threats of Critically Endangered White-rumped Vulture (Gyps bengalensis)
in Mudumalai Tiger Reserve, Southern India”. He
worked a decade for vulture conservation in Tamil Nadu especially Nilgiris Eastern Ghats Landscapes. At present, he is
working the Vulture Safe Zone project in the Bundhalkand
region, Mathiya Pradesh. Dr. B. Ramakrishnan is working as Assistant Professor in
wildlife biology in the Department of Zoology and Wildlife Biology at
Government Arts College, Udhagamandalam. He organized the southern Indian leave
vulture conservation workshop in 2018 to resolve the conservation threats as
well as management recommendations to secure the southern Indian vulture
population. He is currently a member in IUCN-Asian Elephant, SBW-Tamil Nadu,
NBA-Invasive Alien Species, SLSC-NBR, NTCA- Governing Body Mudumalai,
and Sathyamangalam TR.
Author
contribution: AS
conceived and designed the experiments, performed the experiments, and analyzed
the data. AS and BR wrote the paper.
Acknowledgements: Our wholehearted thanks to the principal chief
conservator of forests and chief wildlife warden of Tamil Nadu State for giving
us the necessary permission to carry out the fieldwork. We are grateful to the chief conservator of
forests & field director, deputy director of Mudumalai
and Sathyamangalam tiger reserves, and the district
forest officer of the Nilgiri North Forest Division
for providing permission and all logistical supports to carry out the
fieldwork. This work was not possible without the support of our field
assistants Mr. K. Manigandan, Mr. R. Bomman, and Mr. B. Vishnu for taking a lot of pain in
collecting field data in the forests amidst with elephants and tigers.
Abstract: The present study aimed to assess
the population status, breeding ecology, and conservation threats of Critically
Endangered White-rumped Vulture in Sigur Plateau, Tamil Nadu, India from June 2011 to May
2012. The population of White-rumped vulture was estimated
in the roosting and nesting sites twice in a month. Nesting colonies were
systematically visited four times in a month during the breeding season to
study nesting and breeding ecology. Carcasses and vulture counting was done by
opportunistic count method. Two sets of questionnaires namely ‘precise and
closed’ and ‘broad and open-ended’ were developed to asses
the people’s perception on vulture conservation. The overall population of White-rumped Vultures was estimated about 70 to 115
individuals. In total, 68 nests were
observed in two nesting colonies. Most of the nests (97%) were recorded on Terminalia
arjuna and only 3% on Spondias mangifera. Among the 68 constructed nests, 34 were
incubated and 30 chicks were fledged out from the nests with 88% breeding
success. Feeding behavior was observed from 28
carcasses, Vultures were attended only 15 caracasses
an average of 56.04±3.29 individuals of vultures were recorded. Interestingly,
Elephant (61.8±5.1) and Indian Gaur (58.5±0.3) carcasses were attracted in
greater numbers of vultures in susiquent days
(3.5±0.2) than other carcasses. People’s attitude to vulture conservation was
positive and useful in 90.82% of the cases (n=99). Cattle carcass disposal
method favored to vultures in these regions. The Sigur Plateau
to be declared as “Vulture Sanctuary” in order to legally protect and conserve
the country’s southern-most wild and viable Critically Endangered White-rumped Vulture population in the landscape.
Keywords: Carcass, conservation, feeding behavior, Mudumalai Tiger
Reserve, nest, Nilgiri Hills, population estimation,
vulture sanctuary.
Introduction
White-rumped Vulture Gyps
bengalensis was once abundant in southern and southeastern Asia. Populations of the White-rumped Vulture and other resident Gyps vulture
species have declined very rapidly since the mid-1990s across the Indian
subcontinent (Prakash 1999; Gilbert et al. 2006; Prakash et al. 2007; Chaudhary
et al. 2012). Declines in numbers of the White-rumped
Vulture have exceeded 99.9% in India (Prakash et al. 2007) and the species is
now classified as Critically Endangered (BirdLife
International 2001, 2018). The cause of these declines has been due to the
veterinary drug diclofenac (Green et al. 2004; Oaks et al.2004), which was
widely used to treat livestock in Asia. Vultures are exposed to diclofenac by
feeding on livestock carcasses which contain residues of this drug. Efforts to achieve
the voluntary withdrawal of diclofenac for veterinary use began in 2004. The
license to manufacture veterinary formulations of diclofenac was withdrawn by
the Drug Controller General of India via a letter dated 11 May 2006 addressed
to all the state drug controllers. A similar ban on the veterinary use of
diclofenac was also introduced in Nepal and Pakistan in 2006 and Bangladesh in
2010. Despite the ban of this drug in the veterinary sector since 2006, the spillover of human diclofenac multi-dose formulations into
the veterinary sector has continued to be the major threat along with other
vulture-toxic veterinary drugs (Cuthbert et al. 2016). Vultures play an
important role in the ecosystem by scavenging dead animals (Moleón
et al. 2014) and the sharp decline of vultures in India has impacted disposal
of livestock carcass, sky burial of Zoroastrians and is implicated in increases
in human-related diseases such as rabies (Pain et al. 2003).
In southern India there are six species of vultures,
viz.: Egyptian Vulture Neophron percnopterus, Red-headed Vulture Sarcogyps
calvus, White-rumped Vulture Gyps bengalensis, Long-billed Vulture Gyps indicus
and two migrants namely, Cinereous vulture Aegypius
monachus, and Himalayan Griffon Vulture Gyps himalayensis are found. Some short term and sporadic
studies have been carried out in Tamil Nadu (Davidar
& Davidar 2002; Davidar
2007; Ramakrishnan et al. 2010, 2012, 2014; Praveen et al. 2014; Samson et al.
2014a, 2015, 2016a,b,c, 2017, 2018, 2019; Samson & Ramakrishnan 2017a,b,
2018a,b,c; Ramakrishnan et al. 2018; Kalanithi et al. 2018; Sebastián-González
et al. 2019), Karnataka (Subramanya & Naveen 2006; Thejaswi
2004; Samson et al. 2014b; Samson & Ramakrishnan 2016; Padma 2018; Rajkumar 2018) and Kerala (Sashikumar
2001; Sashikumar & Vishnudas
2018). In Sigur Plateau, populations of the four
resident species excluding Cinereous and Himalayan Griffon vultures mainly
depend on wild carcasses (90%) (Ramakrishnan et al. 2010). Previous studies in
the study area reported that the retaliatory killing of carnivores through
poisoning the carcasses was one of the threats to the vulture population (Davidar & Davidar 2002). The
present study was aimed to assess the population status, breeding ecology, and
conservation threats of Critically Endangered White-rumped
Vulture in Sigur Plateau, Tamil Nadu, India from June
2011 to May 2012.
Study Area
The Sigur Plateau is located
in Mudumalai Tiger Reserve and its strategically
situated between the Nilgiri Hills and the Eastern
Ghats landscape (Figure 1). It covers an area of 778.80km2 at an
average elevation of 280m above mean sea level. The boundaries of the Sigur Plateau are Bandipur
National Park (Karnataka) in the north, Wayanad Wildlife Scantuary
to the west, and Sathyamangalam Tiger Reserve to the
south and east. It harbors a diverse range of wild
animals including Asian Elephant Elephas maximus, Tiger Panthera tigris,
Leopard Panthera paradus,
Indian Gaur Bos gaurus, Chital Axis axis, Sambar Rusa
unicolor, and numerous other important mammal and bird species. The
Critically Endangered Gyps vultures such as Long-billed, White-rumped, & Red-headed vultures and Endangered Egyptian
vultures are also known to occur in this plateau (Ramakrishnan et al.
2012; Samson et al. 2016). The five major streams in the Sigur
Plateau are the Moyar River, the Sigur River, the Avarahalla
River, the Kedarhalla River, and the Gundattihalla River crisscrosses
the Moyar Valley and finally end up into the Bhavanisagar reservoir.
Materials and Methods
Nest site count
A preliminary survey was conducted in June 2011 to
identify the nesting and roosting sites of White-rumped
Vulture in the Sigur Plateau (Image 1). Information
was also gathered from past literature and questionnaire survey was conducted
to the local and tribal people (n=60) in six villages viz. cattle grazers
(n=25), NTFP collectors (n=40) and forest field staff (n=35) to locate roosting
and nesting colonies of White-rumped Vultures in Sigur Plateau. Once the roosting and nesting locations were
confirmed. Population estimation was done twice (15 days interval) in a month.
The rivers and nullas (streams) were thoroughly
searched for nesting sites’ shreds of evidence of White-rumped
Vulture to monitor the population. We divided the age-class of White-rumped Vultures into two categories namely Adult (Fully
matures after five years) and Immature (1–4 years). The population size of
White-rumped vultures was estimated by counting the
individuals in the roosting and nesting sites during the early morning
(06.30–09.30 h) and late evening (17.30–19.30 h) hours. We assumed fidelity of
nesting sites, fixed time of roosting and geographic closure, no movement into
(immigration), or out of (emigration) sites to estimate population size as
described by Baral et al. (2005).
Breeding ecology
To study the nesting and breeding ecology of White-rumped Vulture, each nesting colony was systematically
visited four times (Seven days interval) in a month during the breeding season
(September-2011 to May-2012) to check the status and number of vultures present
in each nest. All nesting colonies’ observations were done using binoculars
(Nikon 52×10) from an appropriate distance (100–300m). The focal animal
sampling method (Altmann 1972) was used to monitor the status and behavior of the White-rumped
Vulture in nesting colonies (Postupalsky 1974;
Acharya et al. 2009). Every visit, five to 10 minutes were spent to check the
breeding status of each nest. All observations were made between 07.00h and 12.00h.
Nests were identified by the presence of fresh nesting materials and whitewash
(excreta) below the nesting tree or by the presence of the incubating vulture
in the nest. All the nests were identified and nesting trees were tagged for
future monitoring (Postupalsky 1974). The nesting
variables such as tree height, Diameter at Brest Height (DBH), trunk size,
primary branch, branch start, branch
end, nest height, number of nests in a tree, nest dimension, nest position, and
nest location were recorded. Tree height was measured using a rangefinder
(Bushnell) and diameter at breast height (DBH) was measured using a measuring
tape. All nesting trees were tagged (using a metal plate by numbering the
nesting trees). The direction of nests on the nesting trees was determined by
compass. Nest locations on trees were determined by visual estimation, viz.,
top of the crown, and limb (offshoot growing directly out of a tree trunk).
Confirmation of active (occupied) and abandoned (unoccupied) nests was done
based on the criteria laid down by Postupalsky
(1974). An active breeding pair was defined as that laid an egg, and
non-breeding pair was confirmed that occupied the nest at least for three weeks
but did not lay an egg. Breeding success was calculated based on the number of
fledglings divided by the number of breeding pairs (that laid eggs). On each
visit, an active nest was considered occupied by a pair by only when a single
or two adult vultures were observed at the nest, one standing and one
incubating or one incubating adult was present or one adult with a chick or a
young chick alone was presented in the nest. A colony was considered as active,
only if it contained at least one active nest with egg (Xirouchakis
& Mylonas
2005).
Counts at carcasses
In this, we counted the number of carcasses found by
the opportunistic count method (Information gathered by forest officials and
local people) as well as the number vultures intake the carcasses. Similarly,
other scavenger animals were also noted. Besides the type of carcass, the cause
of death, type of habitat, domestic or wild, and locations were recorded.
People’s on
vulture conservation
Questionnaire survey was carried out between the
months of April and May 2012 in the villages and settlements located in the
vicinity of vulture colonies to understand inhabitant’s perceptions about
vulture population, carcass disposal methods, livestock holdings, livestock
depredation by wild animals, veterinary practice, forest resource use, and
conservation attitudes. A total of 109 persons were interviewed (87 cattle
holders, six veterinary doctors, and 12 quacks, and four medical shops
keepers). Two sets of questionnaires were developed for this study. One was
‘precise and closed’ and the other one was ‘broad and open-ended’. Most of the
people in this plateau are illiterate, so the questions were asked in local
language for easy communication., Questions were asked concerning diclofenac
usage and knowledge about diclofenac and their perceived effect on vulture
populations and sale of diclofenac in drug stores. Mode of veterinary practice
and treatment to injured livestock was interviewed to the veterinary doctors
and veterinary assistants (quacks).
Statistics and mapping
Statistical analyses were done using past3 statistical
software and mapping on nest locations was done using Quantum GIS 1.7.1walcrow
version computer software with the help of GPS field data.
Result
Population
status
Although three colonies namely Anaikatty,
Jagalikadvu, and Siriyur
were found during our study, the Anaikatty nesting
colony was abandoned by the White-rumped vultures.
Monthly two visits (once in a fortnight) were carried out in two colonies
namely, Jagalikadavu and Siriyur
from June 2011 to May 2012. The numbers recorded are presented in Table 1.
There is a significant variation was found in the numbers of White-rumped Vultures observed between breeding 108.75±2.91 (October–May)
and non-breeding 79.25±2.06 (June– September) seasons in both the vulture
nesting colonies (t=4.74; P<0.0000).
Nesting behavior
The breeding season of White-rumped
Vulture was observed from September 2011 to May 2012. The nesting colonies were
located in the riparian ecosystem of Sigur and Gundattihalla rivers (Figure 2). Two tree species namely Terminalia
arjuna and Spondias mangifera
were utilized for nesting by White-rumped Vultures in
the study area. A total of 31 trees with 51 nests were recorded in the Jagalikadavu nesting colony (49 nests in Terminalia
arjuna and 2 nests in Spondias mangifera). On the other hand, 17 nests were seen in 10
Terminalia arjuna trees at the Siriyur nesting
colony. The mean height of the nesting
tree was 26.73±0.76 and the DBH was 478.43±36.27 irrespective of the tree
species in both the nesting colonies. The maximum height of the nesting tree
was 36m and a minimum height was 17m in the Jagalikadavu
nesting colony. The average trunk size of the nesting trees was 10.15±0.54m
irrespective of the tree species in both the nesting colonies. Similarly, the
branch start and branch end of the nesting trees showed that 9.92±0.54m and
23.80±0.75m respectively. The primary branch was 4.39±0.21m and the canopy size
shows much higher values on length 16.82±0.68 and width 28.63±0.75 the nest
height from the ground level shows 24.72±0.62. The height of the nest location
was ranged from 14m to 36m. White-rumped Vultures
construct cup type nests and the nest dimension was approximately 1m length and
40cm width and 15cm depth. Most of the nests (34%) were positioned towards
north-east direction (NE) (n=23) followed by south-west (SW) (29%; n=20), south-east
(SE) (25%; n=17) and north-west (NW) (12%; n=8) (Figure 3). Most of the nests
were located on the tree crown (n=51) and a considerable number of nests were
located on the limb (n=15) portion of the tree. The percentage of canopy cover
was classified into four categories (0% to 25%, 25% to 50%, 50% to 75% and 75%
to 100%). The result showed that the most nesting trees (n=15) were in the
25%–50% canopy cover, followed by 50%–75% (n=12), 75%–100% (n=9) and 0%–25%
(n=5) (Table 2).
Breeding success
Although nest-building activity of White-rumped Vultures started from September–October, the
intensive nest construction was observed in October (n=48) and nest attendance
by parent birds was until the end of chicks fledged out from the nests (May).
The nests (n=68) were classified as occupied and abandoned. It was unfortunate
to note that the proportion of abandoned nests were gradually increased during
the breeding i.e in the month of October 52% (n=20),
in November 38% (n=14), and in even in December it was 10% (n=4) during nest
construction and egg-laying stages. Among the 68 constructed nests, 50% (n=34)
completed incubation. Of which, 88% (n=30) of nests had successfully hatched,
and all hatched young ones were successfully fledged out. The incubation took
place from November to January (55 to 60 days). Hatchlings were seen from the
first week to the second week of January 2012 (30 chicks). The breeding success
has differed between the nesting colonies. Siriyur
nesting colony (100%) had higher breeding success than the Jagalikadavu
colony (85%) (Table 3). The nesting success in the nesting trees was also
measured in which 56.41% (n=22) was observed from T.arjuna
trees. On the other hand, 100% of the failure of nesting was recorded in S.mangifera trees (n=2). The overall breeding success of both the
nesting trees was 41.07% in T.arjuna followed
by 0% in S.mangifera.
A total of 24 visits, we had observed 30.12±5.36
individuals of both Tufted Grey Langur Semnopithecus
priama and Bonnet Macaque Macaca
radiata were disturbed on the nesting trees. Four broken eggs and eight
destroyed nests were recorded during our fieldwork envisaged that there was a
severe disturbance by these primates.
Observation of carcasses
A total of 28 ungulate carcasses were observed during
the study period, which incuded 16 domestic and 12
wild animals (Table 4). Among the
carcasses, most of them were found near human settlements (n=15) and
considerable numbers were in forest areas (n=13). Out of 28 carcasses, 11 of
them were Tiger kills, just one was Wild Dog kill and others (n=16) were
natural deaths. Vultures were attended only 15 caracasses
an average of 56.04±3.29 individuals of vultures were recorded viz White-rumped
Vultures (51.62±3.1), Long-billed Vultures (2.2±0.2), and Red-headed Vultures
(2.5±0.2). Interestingly, Elephant (61.8±5.1) and Indian Gaur (58.5±0.3)
carcasses were attracted in greater numbers of vultures in subsequent days
(3.5±0.2) than other carcasses. It is
very important to note that out of 15 domestic animal carcasses, just 3
carcasses (2 cow and 1 buffalo) were attended by vultures and the rest of them
(1 buffalo and 11 buffalo calves) were
not attended by vultures. But these 12 carcasses were fed by wild boars (16.2±4.7)
and stray dogs (5.4±2.1) as these carcasses were found very close to human
habitations.
People’s perceptions on vulture conservation
A total of 109 local people were interviewed on
vulture conservation which includes cattle owners and local veterinarian and
drug store owners. Of which, 90.82% (n=99) of them were opined that the vulture
conservation is good for ecosystem services. Interestingly most of them were
opined that the vultures are nature scavengers (73.39%; n=80) and some of them
were also presumed that the vulture is a bird (20.18%; n=22), and few of them
were also opined that the vultures are hunter bird (6.42%; n=7). The questionnaire
survey revealed that most of the cattle holders were illiterate (93.10%; n=81)
and unaware of the drug diclofenac and the threat it poses to vultures. The
respondents opined that the tiger has killed their livestock more (n=252)
followed by leopard and wild dogs each consumed 14 individuals during the last
five years. The mode of livestock carcass disposal by the livestock holders
revealed that most of them were (83.90%; n=73) just throw their carcasses into
forests in the distance between 300-500m from the villages and rests (16.09%;
n=14) were buried their cattle carcasses. All the veterinarians and quacks who
were interviewed responded that they used meloxicam to treat livestock and none
of them used diclofenac through 4 medical shops were selling diclofenac for the
human purpose near vulture habitats in the study area.
DiscussioN
The population of vultures has declined dramatically
across South Asia due to the drug diclofenac, a Non-Steroidal Anti-Inflammatory
Drug (NSAID), and other veterinary drugs (Prakash et al. 2003; Oaks et al.
2004; Margalida et al. 2015). In Sigur
Plateau, the vulture population is possibly protected from some of these drug
effects, as they depend on 90% of their food from wild carcasses (Ramakrishnan
et al. 2010), even though the remaining 10% could still pose risks. The present
study recorded the minimum and the maximum number of White-rumped
Vulture populations viz. 44-98 and 22-38 in Jagalikadavu
and Siriyur colonies respectively from June 2011 to
May 2012. It was quite interesting to note that the vulture population was very
low In June, and gradually increased subsequent months and reached its maximum
numbers at the end of May. A similar pattern was also noted by Baral et al. (2005) in the White-rumped
Vulture population in Nepal. This could be mainly because, during non-breeding
seasons, the adult’s birds fly far away for food, and may not return to nesting
colonies on the same day (Rabenold 1987). Therefore, the maximum number of vultures
were seen in and around nesting colonies only during breeding months, unlike
non-breeding seasons.
The nests were located on the fork of the trees which
are well-foliaged along the watercourses. Similar observations were documented
in India by (Das et al. 2011; Pande et al. 2013; Khan
2013; Ramakrishnan et al. 2014; Majgaonkar et al. 2018; Jha et al. 2020). The present study has
recorded two tree species were preferred by White-rumped
vultures for nest construction in the study area. Of which, more number
(94.12%) of nests on Terminalia arjuna trees and just 4.88% of nests on Spondias mangifera trees
in the riparian ecosystem. Because these two tree species were only seen as
tallest trees in the study area. Similarly, many tree species were preferred by
White-rumped vultures for nest construction across
India and Bangladesh was documented by several authors. Tectona
grandis, Bombax ceiba, Terminalia tomentosa, Dalbergia sissoo in Uttarakhand (Das et al. 2011); Terminalia
arjuna, Terminalia bellerica, Alstonia scholaris, Mangifera indica in
Maharashtra (Pande et al. 2013); Ficus benghalensis,
Ficus religiosa, in
erstwhile East Bengal now Bangladesh (Khan 2013) and Terminalia arjuna
in Tamil Nadu (Ramakrishnan et al. 2014). Road (2010) reported that in Associated
Private Nature Reserves located in the Limpopo Province, South Africa the
African elephants (Loxodonta africana) interfere the nesting habitat and break the
branches as well as debarking the nesting trees and destroyed the nesting trees
of White-backed vultures (Gyps africanus). Similar kind of observation
is observed in Sigur plateau Tusk punch mark on the
nesting trees, debarking as well as feeding on bamboos under the nesting trees
and interestingly note that 20 Honey Hives are recorded in the nesting trees in
four nesting trees Sloth bear hunt the Honey hives we confirmed based on the
nail marks on the bark on the nesting trees. Jha et al (2020) recorded that out
of 44 tree species used by vultures for roosting, 14 (mostly shorter) trees
were not used for nesting, indicating a preference for taller trees in Madhya
Pradesh. Large trees (Chhangani 2007; Dhakal et al.2014) provide predator avoidance,
suitable microclimates (Campbell 2015), and increased mobility (Wright et al.
1986) for vultures. The present study has recorded 14-36m above the ground
level of White-rumped vulture nests in the study area
irrespective of the nesting tree species. 16.6m height was recorded by Chomba & M’Simuko (2013) in
Lochinvar National Park on the Kafue flats, Zambia, 8–28m in central west Nepal
(Subedi & DeCandido
2014), 14.8m in Himachal Pradesh, India (Thakur & Narang 2012), 18–36m (Naoroji 2006), above 21m in southern Pennsylvania, northern
Maryland, and northeastern Virginia (Thompson et al.
1990) and 25–30m in Sigur Plateau of the Nilgiris (Ramkrishnan et al.
2014). Other species were recorded in smaller trees (Mangifera
indica, Acacia nilotica,
Azadirachta indica,
Prosopis cineraria) in other regions such as arid Rajasthan and
Maharashtra (Chhangani 2007; Kambale 2011; Khatri
2013). Among the 68 nests recorded by this study, 34% were facing towards
north-east, 25% south-east, and 29% south-west directions. This was mainly due
to a possible influence of sunlight effect. The maximum nests’ width and length
were 1m and 40cmrespectively. Canopy size plays a huge role for the selection
of nesting trees by White-rumped vultures in the
study area. The average length was 16.82±0.68m and the width was 28.63±0.75m
recorded in the study area.
The present study found that out of 68 constructed
nests, 34 were incubated and 30 chicks were successfully fledged out from the
nests with 88% of breeding success during the year 2011–2012. Sashikumar & Vishnudas (2018) reported an overall 65% breeding success
of White-rumped Vultures in Wayanad Wildlife
Sanctuary, Kerala from 2003 to 2017. Majgaonkar et
al. (2018) reported that overall 21.2% of occupied nests in a coconut
plantation colony affected by storm damage, 52.9% was successful in a nearby
forest colony in western Maharashtra, India. Thakur (2015) reported that 56.1%
breeding success in 2009–2010, and slowly increased to 72.7% in 2010–2011 and
finally 79.4% success in 2011–2012 from 24 breeding colonies of White-rumped Vultures in Shahpur, Nurpur, and Kangra regions in Kangra District of Himachal Pradesh. Baral
et al. (2005) reported that 72–102 individuals of White-rumped
Vultures in six colonies during their breeding season had 50% breeding success
at 70 occupied nests in Rampur Valley, Nepal. In Pakistan, a total of 2,281
occupied nests of White-rumped vultures were recorded
between 2000 and 2004 the nest success was observed in 1,231 nests taking the
breeding success to 51% (Gilbert et al. 2006). The mean nesting success of
African White-backed Vultures (Gyps africanus ) in the Masai Mara over the five years was 59%, which compares favorably with previous studies conducted in southern
Africa (Monadjem 2003; Herholdt
& Anderson 2006). The nesting success rates after the year 2000 for White-rumped Vulture colonies in India, Nepal, and Pakistan
ranged between 30% and 73% (Gilbert et al. 2006; Baral
& Gautam 2007; Thakur & Narang 2012); however, the breeding success of
White-rumped vultures in Bangladesh between 2009 and
2011 was only 15.6% and 25.8% due to the effect of multiple dosages of
diclofenac (Khan 2013). The 88.23% breeding success of White-rumped vultures recorded by this study is a positive sign
envisaged that this population is gradually growing when compared to other
studies across the country and the world as a whole.
We observed a total of 38 (56%) nests were abandoned
by the White-rumped vultures during the breeding
season (October to December 2011) of the study period. Of which, 90% of the
nests were abandoned before eggs were layed (October
to November) and 10% of the nests were abandoned after the eggs were laid
(December). Similar observation was noticed in Nepal by Baral
et al. (2005). Samson et al (2018) reported that anthropogenic threats were
resulted in nest site abandonment by White-rumped
Vultures in Sigur Plateau. Newton (2002) stated that
certain pairs may occupy a territory for only a few days or a few weeks, or may
even build a nest, but the process stops there. He added the major factor
influencing on the egg-laying process in vultures was the food supply, and in
poor food years, territorial pairs in some populations fail to lay eggs. Baral et al (2005) seen that the nest abundance by vultures
due to mortality of chicks in the previous year and Moran-lopez
et al (2006) explained that anthropological threats in the nesting areas would
also cause the nest abandoned behaviour in vultures. This study recorded the Gray langur and Bonnet macaques were caused severe threats
to the breeding population of White-rumped Vultures
(n=8 nests) by jumping or shaking the branches, destroying the nests and
depredation of eggs especially by the Bonnet macaques. A similar observation
was observed in Himachal Pradesh where monkeys were recorded continuously in
nesting site (Pehad nesting site) although, no direct
evidence of interference of the monkey troops with vultures were observed, the
number of vulture nests at Pehad nesting site
decreased from six occupied (breeding season 2009–2010) to one occupied nest
(breeding season 2010–2011), he stated that it may be due to interference by
monkeys. Finally, the vultures at Pehad shifted to a
new nesting site at Chattri (around 1km away) with
three occupied nests (breeding season 2010 to 2011) (Thakur and Narang 2012).
The present study observed the direct impact of Grey langurs and Bonnet
macaques play behavior in both the White-rumped vulture nesting sites in Sigur
plateau. Many studies in Africa
confirmed that the monkeys and baboons interfered in the normal breeding of
African vultures (Mundy et al. 1992; Emmett 2003; Roche 2000 & 2006).
In Sigur Plateau, both the
nesting colonies were located near to human settlements (average of 1.92km).
Green et al. (2004) stated that based on demographic modeling,
less than 0.8% of ungulate carcasses available to foraging vultures would need
to contain a lethal dose of diclofenac for this to have caused the observed
population declines. Therefore, educating livestock holders, farmers, and
veterinary personnel on the usage of diclofenac awareness may help to secure
the vulture population although 93.10% of livestock holders did not aware of
diclofenac and its effects as per this study.
Management Recommendations
- The present study suggests that the creation of
awareness is important among the school children for the schools that are
surrounded by the vulture habitat to bring out future conservationists.
- Declaration
of “Vulture Sanctuary” would support legally for the population. The Karnataka Government has declared a
“Vulture Sanctuary” to conserve another Critically Endangered Long-billed
Vulture species in Ramnagaram Hills, Karnataka as a
first of its kind. The sanctuary was declared for a total of 346.14ha area was
to secure 15–18 individuals and their nesting sites in the hill.
- Sigur Plateau is strategically located at the tri-junction
of three Tiger Reserves namely Mudumalai Tiger
Reserve, Biligiri Rangaswamy
Tiger Reserve, and Sathyamangalam Tiger Reserve. This
would ensure long-term food supply to vultures as they are dependent to tiger
kills majoritivelly than other co-predators
Table 1. Population estimation of White-rumped Vulture in Sigur Plateau,
Western Ghtas, India.
Colonies |
Seasons |
Adult |
Immature |
Total |
|||
Jagalikadavu
+ Siriyur Overall |
Non-breeding (June–September) |
Maximum Minimum |
M±SE |
Maximum Minimum |
M±SE |
Maximum Minimum |
M±SE |
62–50 |
58±1.5 |
28–12 |
21.25±2.04 |
86–70 |
79.25±2.06 |
||
Breeding (October–May) |
84–69 |
77.37±1.15 |
56–20 |
31.37±2.47 |
138–97 |
108.75±2.91 |
|
Jagalikadavu (June 2011–May 2012) |
61–34 |
48.75±1.69 |
40–06 |
18.56±1.56 |
98–44 |
67.04±2.78 |
|
Siriyur (June 2011–May 2012) |
28–10 |
22.16±0.75 |
17–06 |
9.70±0.55 |
41–22 |
31.87±0.91 |
|
Overall |
|
70.91±2.10 |
|
28±2.02 |
|
98.91±3.54 |
Table 2. Nesting trees and nest variables details of
White-rumped Vulture in the Sigur
Plateau, Western Ghtas, India.
Variables |
Nesting trees |
Overall |
|
Terminalia arjuna (N=39) |
Spondias mangifera (N=2) |
||
Height |
27.07±0.75 |
20±1 |
26.73±0.76 |
DBH |
478.43±36.27 |
478±41.5 |
478.43±34.51 |
Trunk Size |
10.15±0.54 |
5.5±0.5 |
9.92±0.54 |
Branch Start |
10.15±0.54 |
5.5±0.5 |
9.92±0.54 |
Branch End |
24.12±0.76 |
17.5±0.5 |
23.80±0.75 |
Main Branches |
4.41±0.21 |
4±1 |
4.39±0.21 |
Canopy size |
16.92±0.71 |
15±1 |
16.82±0.68 |
Nest Height |
24.92±0.63 (n=66) |
18±1 (n=2) |
24.72±0.62 |
Table 3. Nesting success details of White-rumped Vulture nesting colonies from the Sigur Plateau, Western Ghtas,
India.
Nesting colonies |
No of trees |
No of nest constructed |
Nests with eggs |
Nests with hatched chicks |
Confirmed fledged |
Breeding success |
Abandoned or failed nests |
Jagalikadavu |
31 |
51 |
26 |
22 |
22 |
85% |
29 |
Siriyur |
10 |
17 |
8 |
8 |
8 |
100% |
9 |
Total |
39 |
68 |
34 |
30 |
30 |
88% |
38 |
Table 4. Preference of carcasses by vultures in Sigur Plateau, Tamil Nadu, India.
|
Name of the carcasses |
Number of Individuals |
Avg. No of days Observed |
WRV |
LBV |
RHV |
Total |
WB |
SD |
1 |
Buffalo |
1 |
2 |
62±4 |
3±1 |
2.5±0.5 |
67.5 2.5 |
6±2 |
8 |
2 |
Cow |
3 |
2.5 |
36.6±5.7 |
1.6±0.2 |
0.8±0.1 |
39.9±5.6 |
8.1±1.3 |
6.2±2.4 |
3 |
Elephant |
2 |
4 |
56.5±5.4 |
2.1±0.4 |
3.1±0.6 |
61.8±5.1 |
16.6±2.5 |
3±1.4 |
4 |
Indian Gaur |
3 |
3.3 |
53±7.7 |
2.5±0.6 |
3±0.3 |
58.5±0.3 |
5.4±6.95 |
0 |
5 |
Sambar Deer |
3 |
1 |
35.3±3.1 |
1±0.5 |
1±0.5 |
37.3±4.1 |
4.2±1.8 |
0 |
6 |
Spotted Deer |
3 |
1 |
29.3±5.6 |
1.3±0.3 |
1.3±0.3 |
32.3±6.1 |
2.1±0.6 |
0 |
7 |
Buffalo |
1 |
6 |
0 |
0 |
0 |
0 |
18.7±3.4 |
6.21±2.1 |
8 |
Buffalo calf |
11 |
2.5 |
0 |
0 |
0 |
0 |
12.3±3.8 |
4.2±1.9 |
9 |
Indian Gaur calf |
1 |
1 |
0 |
0 |
0 |
0 |
8 |
0 |
WRV—White-rumped Vulture |
LBV—Long-billed Vulture | RHV—Red-headed Vulture | WB—Wild Boar | SD—stray dogs
For
figures & image - - click here
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