Papers by Rohit Naniwadekar
The fruit-tracking hypothesis predicts a positive association between frugivores and fruit abunda... more The fruit-tracking hypothesis predicts a positive association between frugivores and fruit abundance over space and time. We documented hornbill diets and examined the relationship between fruit abundance and abundance of three hornbill species (Buceros bicornis, Rhyticeros undulatus and Aceros nipalensis) in the Eastern Himalaya from 2009-2012. The study was carried out at three scales: at the largest scale of the study area (15 km 2 ), at the intermediate scale -eight 3-ha patches within the study area and at the smallest scale of individual fruiting trees. Ninety-one per cent of the 64 foraging sightings of the great hornbill were on figs while more than 50% of the foraging sightings of the wreathed (83) and rufous-necked hornbills were on non-fig fruits. At the largest scale, wreathed hornbill abundance and ripe fruit abundance peaked in the non-breeding season. At the intermediate scale, wreathed hornbill abundance was positively associated with non-fig fruit availability while rufous-necked hornbill abundance was negatively associated with non-fig fruit availability. At the smallest scale, great and rufous-necked hornbill abundances were correlated with fig and non-fig fruit crop sizes, respectively. The three hornbill species track fruit availability at different scales based on diet, which has implications for their role in seed dispersal.
Biotropica, 2015
Seed dispersal studies have primarily examined dispersal as a function of distance from the paren... more Seed dispersal studies have primarily examined dispersal as a function of distance from the parent tree and/or heterogeneity in dispersal due to animal use of nesting, roosting and sleeping sites. However, non-random heterogeneity in seed dispersal is also likely to result from the post-foraging behavior and movement of frugivores which prefer certain trees. To characterize variation in seed rain at fine scales, we studied the dispersal curve of Prunus ceylanica, a primarily bird-dispersed species. We compared seed rain at conspecifics, heterospecific fruiting trees with similar frugivore assemblages, emergent trees, and the landscape surrounding these trees. Seed rain of P. ceylanica was found to peak globally under the canopy of conspecifics but to peak locally under the canopy and immediate neighborhood of heterospecific fruiting trees. Our results demonstrate that seed rain is highly clumped even at fine spatial scales. A large proportion of seeds are dispersed in specific, localized regions. This variation can have important implications for plant population dynamics and might significantly alter the impact of post-dispersal processes. Seed dispersal models may need to incorporate this heterogeneity to explain manifestations of spatially explicit dynamics like mixed species 'orchards'.
For most of Northeast India's diverse assemblage of small carnivores, direct observations and eco... more For most of Northeast India's diverse assemblage of small carnivores, direct observations and ecological information are limited. Opportunistic direct observations and camera-trap records from 2008 to 2013 in eastern Arunachal Pradesh recorded 11 small carnivore species of the 20 likely to occur. Observations included the first confirmed Small-toothed Palm Civet Arctogalidia trivirgata sighting from India; dietary observations on five species; and hunting of two species.
Asian hornbill populations are declining across their ranges because of hunting and deforestation... more Asian hornbill populations are declining across their ranges because of hunting and deforestation. Five of the 32 Asian hornbill species occur in north-east India. However, vital information on their abundance from the region remains scanty. Understanding spatiotemporal variation in densities provides crucial information for formulating effective conservation strategies based on species-specific abundance patterns and population trends. We examined spatiotemporal variation in densities of four hornbill species in the Namdapha Tiger Reserve, a site identified as an important site for hornbill conservation in Asia. We collected data through variable-width line transect sampling (effort=842.1 km) in the non-breeding season from 2009-12 to estimate hornbill densities. We had 458 detections of four hornbill species. We have estimated White-throated Brown Hornbill densities (7.9 birds/km 2 ) for the first time throughout its entire range. The mean Rufous-necked Hornbill densities (6.9 birds/km 2 ) were higher than those reported elsewhere. Great (3.9 birds/km 2 ) and Wreathed Hornbill (16.1 birds/km 2 ) densities were comparable with other sites. The peak densities of all hornbill species in November-December are among the highest reported from Asia. Wreathed Hornbill densities showed temporal variation peaking in November-December (68 birds/km 2 ) and drastically declining by March-April (1.3 birds/km 2 ), indicating seasonal altitudinal movement to lowelevation areas outside the reserve during the breeding season. Our results underscored the spatial variation in hornbill distribution, with low densities of Great and the White-throated Brown hornbills in higher elevations. Our study demonstrates the global importance of Namdapha for hornbills, given its large area and high densities of four hornbill species.
Aim To examine patterns in anuran species richness along an elevation gradient and identify facto... more Aim To examine patterns in anuran species richness along an elevation gradient and identify factors that govern anuran species richness on a tropical elevational gradient. during the north-east monsoon and dry seasons, using transects (50 · 2 m) and visual encounter surveys along the streams. The entire gradient was classified into thirteen 100-m elevation zones. Sampling at the alpha (single drainage basin) level was carried out in the Chinnapul River drainage basin (40-1260 m a.s.l.) and at the gamma (landscape) level in four drainage basins. Additionally, published records were used to arrive at an empirical species richness (S) for the entire landscape. Mid-Domain Null software was used to test for the possible influence of geometric constraints on anuran species at both the alpha and gamma levels. The influence of area under each elevation zone on empirical S was tested. The pattern in anuran species richness along the elevational gradient was investigated using: (1) species boundaries in each elevation zone and their habitat correlates, (2) abiotic factors as predictor variables, (3) mean snout vent lengths of anurans, and (4) correlation between the matrices of distance in the elevation zones based on microhabitat parameters and species composition. Cluster analysis on species presence-absence in the elevation zones was used to categorize the entire gradient into high, middle and low elevations. In these three elevation categories, pattern in composition of species was examined for endemism in Western Ghats-Sri Lanka biodiversity hotspot, uniqueness to an elevation zone, adaptations of adults and modes of breeding.
Relative abundance index Tiger Ungulates A B S T R A C T Illegal hunting poses a dual threat to l... more Relative abundance index Tiger Ungulates A B S T R A C T Illegal hunting poses a dual threat to large carnivores through direct removal of individuals and by prey depletion. We conducted a camera-trapping survey in the Namdapha National Park, north-east India, conducted as part of a programme to evaluate carnivore and prey species abundance. Clouded leopard (Neofelis nebulosa) was the only large carnivore detected by camera-trapping. Indirect evidences indicated the presence of the wild dog (Cuon alpinus) and leopard (Panthera pardus), however, there was no evidence of tigers (Panthera tigris), suggesting their possible extinction from the lower elevation forests. Of the major ungulate prey species, sambar (Cervus unicolor) and wild pig (Sus scrofa) were the only large prey detected, while the Indian muntjac (Muntiacus muntjak) was the only small prey species detected. Relative abundances of all species were appreciably lower than estimates from other tropical forests in south-east Asia. We suspect that illegal hunting may be the cause for the low carnivore and prey species abundance. An ongoing community-based conservation programme presents an opportunity to reduce local people's dependence on hunting by addressing their socio-economic needs and for using their skills and knowledge of the landscape for wildlife conservation. However, long-term wildlife monitoring is essential to assess the efficacy of the socio-economic interventions in bringing about wildlife recovery.
A new tree skink species of the genus Dasia Gray, 1830, closely allied to Dasia haliana, is descr... more A new tree skink species of the genus Dasia Gray, 1830, closely allied to Dasia haliana, is described from southern Western Ghats of India. The new species named, Dasia johnsinghi sp. nov. can be distinguished from all other congeners by morphological and molecular data. A related species, Dasia subcaeruleum, is re-described based on new material from a new locality in the Western Ghats. Mitochondrial rDNA-based phylogenetic analysis of the genus Dasia reveals the affinities of the south Indian and the Sri Lankan species with Southeast Asian ones. The biogeographic processes that might have led to the disjunct distribution of the entities in the genus are discussed. An updated key to the identification of species of the genus Dasia is provided.
Uploads
Papers by Rohit Naniwadekar