Papers by Dipankar Lahkar
Estimating leopard densities when populations comprise polymorphic phenotypes: an application of spatial mark-resight models
BioRXIV (Preprint), 2020
Melanism is a form of pigmentation polymorphism where individuals have darker coloration than wha... more Melanism is a form of pigmentation polymorphism where individuals have darker coloration than what is considered the “wild” phenotype. In the case of leopards, Panthera pardus, melanism occurs at higher frequencies amongst populations in tropical and subtropical moist forests of south and southeast Asia, presenting a unique challenge in estimating and monitoring populations in these regions. Unlike the wild phenotype that are readily recognizable by their rosette patterns, melanism results in a subset of individuals being ‘unmarked’ or unidentifiable through photographic captures obtained using white flash cameras. While forcing infrared flash camera traps into night mode allows for individuals to be identified and population density estimated using spatial capture-recapture analysis, spatial mark-resight (SMR) models that require only a subset of the population to be ‘marked’ offer an alternative in situations where both phenotypes occur and photographic capture-recapture sampling is carried out with white flash cameras. In this study, we present an application of SMR models to estimate leopard densities using camera trap survey data from three sampling sessions at Manas National Park (MNP), India. By using an SMR model that allowed us to include captures of unidentified sightings of marked individuals, we were also able to incorporate captures where identity was either not confirmed or only known from a single flank (either right or left). Following 18,674 trap-days of sampling across three sessions, we obtained 728 leopard photo-captures, of which 22.6% (165) were melanistic. We estimated leopard densities of 4.33±SE 0.18, 2.61±0.15 and 3.37±0.14 individuals/100km2 across the three sessions. To our best knowledge, these represent the first known estimates of leopard densities from such populations. Finally, we highlight that SMR models allow for the estimation of population densities of leopards and other species that exhibit phenotypic polymorphism and present an opportunity to revisit past camera trap survey data for such species towards generating valuable information on populations.
Responses of a wild ungulate assemblage to anthropogenic influences in Manas National Park, India
Biological Conservation, 2020
Large carnivores have experienced significant global range contractions and recovering their popu... more Large carnivores have experienced significant global range contractions and recovering their populations is often
contingent on increasing prey abundances. In Manas National Park (MNP), following nearly two decades of
ethnopolitical conflict, studies document that populations of both prey and predators were depressed. Here we
assess the status of wild ungulates in a section of MNP (Bansbari-Bhuyanpara) that has remained conflict-free for
over a decade. For seven ungulate species, we estimate species-specific densities using distance-based sampling,
assess species-specific space-use patterns in relation to habitat variables within an occupancy framework and
examine patterns of temporal activity in relation to times when people access the park for resources. Further, by
comparing temporal activity patterns of ungulates between MNP, a site where local communities access the park
for resources, and Kaziranga National Park, where human use of the park is minimal, we examine if species
activity is altered in response to human presence. We estimate that currently Bansbari-Bhuyanpara ranges of
MNP support 42.66 (34.16–51.16) individual ungulates/km2. Our results highlight that current patterns of
human access within the park affect both spatial and temporal behaviour of these species. Although we estimate
a relatively high recovery potential for tigers in MNP given current prey densities, we suggest that further
ungulate population recoveries could be supported in the park. With several ungulate species experiencing
range-wide declines, efforts to minimize non-lethal human disturbances on these species also need to be considered
to ensure that predator-prey systems remain intact.
Information on the presence and distribution of species is crucial for conservation planning and ... more Information on the presence and distribution of species is crucial for conservation planning and management within a region. Documentation of species assemblages in Manas National Park (MNP) in the aftermath of conflict is critical for informed conservation
interventions. For nearly two decades (1990–2010), conservation efforts in MNP were compromised by ethno−political conflict. We
conducted camera trapping surveys of terrestrial mammals across three administrative forest ranges (Panbari, Bansbari and Bhuyanpara)
of MNP in 2017. A systematic survey with 118 trap locations accumulated data over 6,173 trap-days. We obtained 21,926 photographs
of mammals belonging to 13 families and 25 species, of which 13 are threatened. We calculated photographic capture rate index
(PCRI) using independent events. Trap specific PCRI’s were used to map the spatial variation in capture rates. We observed variation in
capture rate between Bansbari-Bhuyanpara where conflict ended in 2003 and has remained peaceful, and Panbari, a forest range where
conflict ended later in 2016. Our results further indicate lower capture rates of mammalian prey species and small felids, but higher
capture rates of four large carnivores in Panbari as opposed to Bansbari-Bhuyanpara. These results highlighted the fact that despite
a history of ethno-political conflict in the region, although almost all mammalian species expected to occur in the park were detected
and confirmed, present evidence indicated ethno-political conflict influences the distribution of several key species. In depth studies
assessing mammalian prey densities, distribution and density are required to further understand the effects of conflict.
Some of the observations of the Breeding behaviour of critically Endangered Gyps species of vulture in captivity. Newsletter for Birdwatcher.
Some observations of the population status of Red Jungle-fowl in Pilibhit Reserve forest. Newsletter for Birdwatcher. Vol. 51. No. 4, pp. 53-54.
Dipankar Lahkar, R. S. Sekhawat, S. Yadav (2011). First Sighting of River Lapwing in Ranthambhore Tiger Reserve, India. Newsletter for Birdwatcher
Population study of water birds was conducted in two wetlands 'Raital Bandh' and 'Jalkil Bandh' o... more Population study of water birds was conducted in two wetlands 'Raital Bandh' and 'Jalkil Bandh' of the Sunabeda Wildlife Sanctuary, Odisha, India, in two successive years 2009 and 2010. 4,701 birds of 29 species belonging to 12 families were recorded during two years. Highest number of waterbirds were observed in Raital Bandh during both years. All total eight winter and twenty one resident species were identified during the study period. The family Anatidae (46.67% and 51.30%) in Raital Bandh and 60.79% and 58.14% respectively in Jalkil Bandh forms the main bulk of the waterbirds population. Species diversity was found highest in Raital Bandh in 2009 (1.398) and in 2010 Jalkil Bandh (1.342). The depth of the water and siltation was the major problem in winter of these two wetlands. Illegal activities like netting, killing of wild birds are continuously major threats for the conservation. Twenty nine (29) species of water birds belonging to 12 families were identified among 4,701 individual counted during 2009 and 2010 in Raital and Jalkil water bodies. Indian Forester, 139 (10) : 906-911, 2013
Blue-tailed Bee-eater (Merops philippinus) is a colourful bee-eater larger than Small Green Bee-e... more Blue-tailed Bee-eater (Merops philippinus) is a colourful bee-eater larger than Small Green Bee-eater (Merops orientalis), has a b l a c k s t r i p e t h r o u g h t h e e y e s , d e e p chestnut throat and breast, bright blue rump and tail (Ali, 1996). It resembles Bluecheeked Bee-eater (Merops superciliosus) in appearance.
103 genera and 46 families is heartening indeed. Their continued existence by and large indicates... more 103 genera and 46 families is heartening indeed. Their continued existence by and large indicates that these birds have one way or another, adapted to the severe environmental conditions of Barmer District. While a third of the birds recorded (56 species) were widespread residents, 22 species were sparse locals, which go to show that they have adapted well to all the seasons. However, a quarter of the species (43) were classified as winter visitors or summer visitors or passage migrants. Yet, the status of the remaining 27 species could not be ascertained.
The entire study was carried out by observing the birds (White-backed, Long-billed and Slender-bi... more The entire study was carried out by observing the birds (White-backed, Long-billed and Slender-billed Vulture) in the three Colony aviaries (CA) (100x40x20 ft) through the CCTV (Close Circuit Television Camera) monitors. During the study attempt was made to determine the feeding hierarchy among vultures, food consumption by individual vultures and time taken for it. In the CA-2 birds (WBV) start feeding almost as soon as the food was provided (within 15 minutes) and they fed throughout the day. In CA-3(SBV) birds came on an average 23.16 hrs after food was provided but majority of them finished within an hrs. In CA-1 (LBV) birds also took more than 24 hrs to starts feeding after the food was provided. A vulture is fed 3 kilos of goat meat in a week which is equivalent to consuming 5% of its body weight per day. WBV with nestlings of different age groups were observed for studying the role of sexes in feeding the nestlings. On an average, the parents fed the nestling for 6.4 times, when nestling was less than 30 days. Male however feed the nestling during mornings and female during evenings. The feeding frequency decreased with the growth of the nestling.
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Papers by Dipankar Lahkar
contingent on increasing prey abundances. In Manas National Park (MNP), following nearly two decades of
ethnopolitical conflict, studies document that populations of both prey and predators were depressed. Here we
assess the status of wild ungulates in a section of MNP (Bansbari-Bhuyanpara) that has remained conflict-free for
over a decade. For seven ungulate species, we estimate species-specific densities using distance-based sampling,
assess species-specific space-use patterns in relation to habitat variables within an occupancy framework and
examine patterns of temporal activity in relation to times when people access the park for resources. Further, by
comparing temporal activity patterns of ungulates between MNP, a site where local communities access the park
for resources, and Kaziranga National Park, where human use of the park is minimal, we examine if species
activity is altered in response to human presence. We estimate that currently Bansbari-Bhuyanpara ranges of
MNP support 42.66 (34.16–51.16) individual ungulates/km2. Our results highlight that current patterns of
human access within the park affect both spatial and temporal behaviour of these species. Although we estimate
a relatively high recovery potential for tigers in MNP given current prey densities, we suggest that further
ungulate population recoveries could be supported in the park. With several ungulate species experiencing
range-wide declines, efforts to minimize non-lethal human disturbances on these species also need to be considered
to ensure that predator-prey systems remain intact.
interventions. For nearly two decades (1990–2010), conservation efforts in MNP were compromised by ethno−political conflict. We
conducted camera trapping surveys of terrestrial mammals across three administrative forest ranges (Panbari, Bansbari and Bhuyanpara)
of MNP in 2017. A systematic survey with 118 trap locations accumulated data over 6,173 trap-days. We obtained 21,926 photographs
of mammals belonging to 13 families and 25 species, of which 13 are threatened. We calculated photographic capture rate index
(PCRI) using independent events. Trap specific PCRI’s were used to map the spatial variation in capture rates. We observed variation in
capture rate between Bansbari-Bhuyanpara where conflict ended in 2003 and has remained peaceful, and Panbari, a forest range where
conflict ended later in 2016. Our results further indicate lower capture rates of mammalian prey species and small felids, but higher
capture rates of four large carnivores in Panbari as opposed to Bansbari-Bhuyanpara. These results highlighted the fact that despite
a history of ethno-political conflict in the region, although almost all mammalian species expected to occur in the park were detected
and confirmed, present evidence indicated ethno-political conflict influences the distribution of several key species. In depth studies
assessing mammalian prey densities, distribution and density are required to further understand the effects of conflict.
Books by Dipankar Lahkar