Optimizing the size of the area surveyed for monitoring a Eurasian lynx(Lynx lynx)population in the Swiss Alps by means of photographic capture–recapture

We studied the influence of surveyed area size on density estimates by means of camera-trapping in a low-density felid population(1-2 individuals/100 km^(2)).We applied non-spatial capture-recapture(CR)and spatial CR(SCR)models for Eurasian lynx during winter 2005/2006 in the northwestern Swiss Alps by sampling an area divided into 5 nested plots ranging from 65 to 760 km^(2).CR model density estimates(95%CI)for models M_(0)and M_(h)decreased from 2.61(1.55-3.68)and 3.6(1.62-5.57)independent lynx/100 km^(2),respectively,in the smallest to 1.20(1.04-1.35)and 1.26(0.89-1.63)independent lynx/100 km^(2),respectively,in the largest area surveyed.SCR model density estimates also decreased with increasing sampling area but not significantly.High individual range overlaps in relatively small areas(the edge effect)is the most plausible reason for this positive bias in the CR models.Our results confirm that SCR models are much more robust to changes in trap array size than CR models,thus avoiding overestimation of density in smaller areas.However,when a study is concerned with monitoring population changes,large spatial efforts(area surveyed≥760 km^(2))are required to obtain reliable and precise density estimates with these population densities and recapture rates.

Hunting of hunted:an ensemble modeling approach to evaluate suitable habitats for caracals in India

Background:Large-scale hunting and various anthropogenic pressures in the recent past have pushed the Asiatic caracal(Caracal caracal schmitzi),an elusive medium-sized and locally threatened felid species towards local extinction in India.Though widely distributed historically,it has been sparsely reported from several regions of central and northern states in India till twentieth century.Later,the species distribution became confined only to the states of Rajasthan,Gujarat and Madhya Pradesh,which have had reported sightings in the twenty-first century.In order to highlight the potentially suitable habitats for Asiatic caracals in India,we targeted forth-filtering of the spatial model ensemble by creating and utilizing the validated and spatially thinned species presence information(n=69)and related ecological variables(aridity,NDVI,precipitation seasonality,temperature seasonality,terrain ruggedness),filtered with anthropological variable(nightlight).Results:Out of eight spatial prediction models,the two most parsimonious models,Random Forest(AUC 0.91)and MaxEnt(AUC 0.89)were weighted and ensembled.The ensemble model indicated several clustered habitats,covering 1207.83 km^(2)areas in Kachchh(Gujarat),Aravalli mountains(Rajasthan),Malwa plateau(Rajasthan and Madhya Pradesh),and Bundelkhand region(Madhya Pradesh)as potentially suitable habitats for caracals.Output probabilities of pixels were further regressed with converted vegetation height data within selected highly potential habitats,i.e.,Ranthambore Kuno Landscape(RKL)(suitability~0.44+0.03(vegetation height)^(**),R^(2)=0.27).The regression model inferred a significant positive relation between vegetation height and habitat suitability,hence the lowest ordinal class out of three classes of converted vegetation height was masked out from the RKL,which yielded in an area of 567 km^(2) as potentially highly suitable habitats for caracals,which can be further proposed as survey areas and conservation priority areas for caracals.Conclusion:The study charts out the small pockets of landscape in and around dryland protected areas,suitable for caracal in the Indian context,which need attention for landscape conservation.