Apte D.,Bombay Natural History Society |
Dutta S.,Wildlife Institute of India
Systematics and Biodiversity | Year: 2010
Compounding effects of slow life-history traits and adult-specific overharvesting have caused a range-wide decline of several giant clam populations. Erratic changes in these populations reported at isolated reefs, are attributable to stochasticfluctuations in recruitment and survival rates. These population rate parameters may be adversely influenced by theconsiderable and increasing human-reef economic interactions in tropical waters. The unsubstantiated knowledge on suchinfluences hinders conservation management of species-habitat linkages particularly for species like the small giant clam(Tridacna maxima). Our study reports small giant clam survival rate, its ecological determinants and stochastic fluctuations from shallow lagoon waters of Lakshadweep Archipelago; a natural habitat not subjected to commercial giant clamharvesting. Survival rate was estimated by monitoring the status of identified individuals in belt-transects throughsuccessive years 2005-2009. The role of different factors in explaining the variation in survival rates was investigated at relevant scales: anthropogenic pressure at the population level in the reef, clam density at sub-population level in the belt-transects, and variables related to clams at the individual level. Effects were quantified through univariate regression techniques and Kaplan-Meier estimator coupled with generalized linear (logit link) models. Small giant clam survival rate in the reef decreased and its spatio-temporal fluctuations increased along the increasing gradient of human populations.Survival was density-independent. Size/age specific survival followed Siler distribution characterized by very low early-age survival, increased adult-age survival, and low older-age survival. Anchorage in coral substrate exerted a curvilinear effect,where survival of moderately anchored clams > loosely anchored clams ≫ deeply embedded clams. Our studyrecommends regular population monitoring in densely inhabited islands to detect incipient changes, which can subsequently be confronted by scientific lagoon bed management. © 2010 The Natural History Museum.
Manakadan R.,Bombay Natural History Society
Journal of the Bombay Natural History Society | Year: 2014
Grassland bird composition was studied in grazed (village grazing lands) and ungrazed grasslands (grassland enclosures of the Forest Department) at Rollapadu Wildlife Sanctuary from August 1992 to July 1994, using belt transect sampling. A total of 32 grassland dependent birds (21 resident, d winter migrant, and 7 seasonal migrant) were recorded in both the habitat types. Of these, 25 species were recorded in each of the two habitat types with 20 of them common to both. Although based on small sample size, our study showed that the species composition differed between grazed and ungrazed grasslands. Five species common in grazed grassland (Indian Courser Cursorius coromandelicus, Red wattled Lapwing VaneUus indicus. Red-winged Bush-Lark Mirafra erythroptera. Rufous-tailed Finh-Lark Ammomanes phoenlcurus, and Plain Prinia Prinia inornata) were not recorded in ungrazed grassland, while two species common in ungrazed grassland (Zitting Cisikola Cislicola juncidis and Black Drongo Edolius macrocercus) were not recorded in grazed grassland. The abundance of certain bird species differed between the grazed and ungrazed grassland. Ungraded grassland had higher numbers of Oriental Skylark Alauda gidgula, while tlie numbers of Sykes's Crested Lark Galerida deva, Ashy-crowned Sparrow-Lark Eremopterix grisea, and Yellow-wattled Lapwing Vanellus malabaricus were greater in grazed grassland. These differences could be due to the impact of livestock grazing, protection, the interaction of relative abundance of food resources and foraging strategy of birds, anchor other unknown factors. The study suggests that mosaics of grazed and ungrazed grasslands may result in an increase in grassland bird diversity. However, since the majority of Indian grasslands arc grazed, we recommend the establishment of more grazing-frcc refuges encompassing different grassland types, to conserve bird species intolerant to grazing. There necessarily has also to be a landscape-level conservation strategy since live majority of India's grasslands have high human dependence, and thus, their conservation requires the support of local communities in the long run.
Dutta S.,Wildlife Institute of India |
Rahmani A.R.,Bombay Natural History Society |
Jhala Y.V.,Wildlife Institute of India
European Journal of Wildlife Research | Year: 2011
The endemic great Indian bustard (GIB) is evolutionarily trapped between open nesting and k-selection that endangers its persistence under prevailing levels of habitat loss and hunting. A global population of about 300 birds is further fragmented into eight populations in the states of Rajasthan (shared with Pakistan), Maharashtra, Andhra Pradesh, Gujarat, Karnataka, and Madhya Pradesh in India. The largest population of 100-125 birds exists in Jaisalmer, Barmer, and Bikaner districts of Rajasthan. Remaining populations number less than 35 birds each. Prevalent GIB conservation strategies use legislation to (a) secure traditional breeding areas by declaring small Protected Areas (PA) or (b) protect vast areas with varied human land uses. The vagrant nature of GIB reduces the benevolent effect of small PAs, while large reserves alienate people by curbing legitimate subsistence rights through strict legislation. These factors along with ill-informed habitat management challenge the current PA approach, even causing local extinctions. Population viability analysis shows that GIB populations of ≤35 birds can persist only under unrealistic conditions of first year mortality ≤40%, and no human caused mortality of adult birds. Even the largest population (≥100 birds) is sensitive to additional loss of adult birds to human causes. With current levels of hunting in Pakistan, extinction is a real threat. A landscape conservation strategy using conservation/community reserve concept that includes controlled traditional land uses with GIB-friendly infrastructural development is needed. The declining rate of GIB populations calls for immediate commencement of ex situ conservation breeding programs. © 2010 Springer-Verlag.
Agarwal I.,Indian Institute of Science |
Giri V.B.,Bombay Natural History Society |
Bauer A.M.,Villanova University
Zootaxa | Year: 2011
A new species of gecko, Hemidactylus graniticolus sp. nov. is described from Karnataka state, south India. This largesized (SVL to at least 110.6 mm), rupicolous gecko differs from congeners in having 16-18 longitudinal rows of fairly regularly arranged, subtrihedral, weakly keeled, striated tubercles at midbody; 9-11 and 12-13 subdigital lamellae on the first and fourth digits, respectively, of both manus and pes; tail with transverse series of four enlarged tubercles on each tail segment; 23-28 femoral pores on each side separated by 1-3 poreless scales; 12-14 supralabials and 9-11 infralabials. Molecular data support the distinctiveness of the new species and its affinities with large-bodied, tuberculate Hemidactylus spp. from India and Sri Lanka. © 2011. Magnolia Press.
Bagchi R.,Durham University |
Bagchi R.,Universitatstrasse 16 |
Crosby M.,BirdLife International |
Huntley B.,Durham University |
And 11 more authors.
Global Change Biology | Year: 2013
We forecasted potential impacts of climate change on the ability of a network of key sites for bird conservation (Important Bird Areas; IBAs) to provide suitable climate for 370 bird species of current conservation concern in two Asian biodiversity hotspots: the Eastern Himalaya and Lower Mekong. Comparable studies have largely not accounted for uncertainty, which may lead to inappropriate conclusions. We quantified the contribution of four sources of variation (choice of general circulation models, emission scenarios and species distribution modelling methods and variation in species distribution data) to uncertainty in forecasts and tested if our projections were robust to these uncertainties. Declines in the availability of suitable climate within the IBA network by 2100 were forecast as 'extremely likely' for 45% of species, whereas increases were projected for only 2%. Thus, we predict almost 24 times as many 'losers' as 'winners'. However, for no species was suitable climate 'extremely likely' to be completely lost from the network. Considerable turnover (median = 43%, 95% CI = 35-69%) in species compositions of most IBAs were projected by 2100. Climatic conditions in 47% of IBAs were projected as 'extremely likely' to become suitable for fewer priority species. However, no IBA was forecast to become suitable for more species. Variation among General Circulation Models and Species Distribution Models contributed most to uncertainty among forecasts. This uncertainty precluded firm conclusions for 53% of species and IBAs because 95% confidence intervals included projections of no change. Considering this uncertainty, however, allows robust recommendations concerning the remaining species and IBAs. Overall, while the IBA network will continue to sustain bird conservation, climate change will modify which species each site will be suitable for. Thus, adaptive management of the network, including modified site conservation strategies and facilitating species' movement among sites, is critical to ensure effective future conservation. © 2012 Blackwell Publishing Ltd.