Evaluation of Population Estimation Sampling Techniques and Assessment of Genetic Diversity of Greater One-Horned Rhinoceros (Rhinoceros unicornis) Population in Dudhwa National Pa: Population in dudhwa national park, uttar pradesh, India

Abstract

The ideology of wildlife conservation emerged with the realization that the wildlife numbers are on a decline in the natural habitats. Since, due to humane limitations we cannot ascertain the exact numbers of a individuals very accurately, therefore, the basic requirement for population estimation arises. Greater one-horned rhinoceros (Rhinoceros unicornis) , already being declared a globally threatened species, demands much attention towards their surviving numbers in wild. Moreover, with the constant rise in the unethical and illegal human activities, the need to regularly monitor their population is realized. To suffice this requirement, population estimation is largely done in a crude way i.e. by labor intensive block count method in which the probability of missing individuals in dense vegetation is high. Advanced population estimation techniques such as capture-recapture using photographic or DNA fingerprint based individual identification, show promising results within the framework of resources in comparison to use of footprint and dung count methods.The current study was conducted in Rhino Reintroduction Area (RRA) of 27 km2 located in Dudhwa National Park. The first objective was to evaluate four population estimation techniques - non-invasive faecal DNA based capture mark recapture (CMR), photographic CMR, dung count and footprint analysis, for their validity in estimation of rhinoceros population with respect to accuracy and precision. The following techniques have been selected out of the others because of their reasonable accuracy and precision obtained when applied to other megaherbivore (including other species of rhinoceros or elephant) population estimation. I selected Dudhwa National Park (DNP) where the reintroduced rhinoceros population is surviving since 1984-85, with a known population size (32 individuals) so as to compare our estimates. For non-invasive faecal DNA CMR technique 140 fresh dung samples were collected and out of them 27 unique genotypes were identified by microsatellite analysis. The capture history of these unique genotypes was then analyzed in MARK to arrive at a population estimate. In photographic CMR, 4 remotely triggered camera trap units were deployed in 6 sessions having 7 occasions in each session. For dung count, random elephant transects of length varying from 1 km to 3.2 km were run and dung piles were counted on either sides. The data on dung density was analyzed in DISTANCE. For dung decay rate estimation 20 fresh dung piles were marked in each of the four habitat types and monitored for decay. The defecation rate was estimated by observing captive rhinoceros. In case of footprint technique, a foot ruler was kept besides each rhinoceros footprint before capturing its photograph. Twenty four (length, angle and area) parameters were extracted from the images using Sigma SCANPRO. The resulting variables were subjected to principle component analysis (PCA) to check for the corresponding variance values in differentiating individual footprints. It was found that the· non-invasive faecal DNA based population estimation and photographic capture mark recapture were the better ones as compared to the other two. However, the data analysis for the dung count and footprint analysis techniques is still under consideration and does not form part of this thesis. These two techniques require further logical modification in study design and statistical analysis to achieve at a reliable estimate. Between the former two, non-invasive faecal DNA based population estimation technique estimated population size (35.10 ± 5.01) close to the known population size of 32. Photographic capture recapture estimated the population size as (25.98 ± 4.91) which was comparatively less accurate than non-invasive faecal DNA CMR. Knowledge of the genetic status of a confined and isolated population is always beneficial to evaluate their well-being and to avoid any future threat such as that of inbreeding depression. Therefore, second objective of the study> was to describe genetic structure of this isolated and reintroduced population. With 27 identified unique genotypes and 10 rhinoceros specific micro satellite markers the genetic variability in this population was examined. It was found that the mean observed heterozygosity level was 0.353 while mean expected heterozygosity level was 0.483. The effective number of alleles per loci was 2.069. When compared to the genetic diversity of the ancestral population in India and Nepal, evaluated in previously published studies, the following results indicated that this population carries lower genetic variability than ancestral populations. The inbreeding test revealed that the population shows signs of inbreeding (Fls = 0.39) and which are likely to exaggerate in future as it is more or less closed and non-randomly interbreeding. Focusing on the conservation needs from management viewpoint we suggest that it is necessary to 'bring variability in the genetic structure to avoid future dire consequences of inbreeding depression. This can be achieved either by translocating new individuals, preferably males, from other Indian sub-populations of Assam or West Bengal since they have better genetic diversity than the-rhinoceros in Nepal.