Niche modelling, current distribution and future scenarios for the otters in Himalayas

Otters (Family Mustelidae; Subfamily Lutrinae) are considered bioindicators of the wetlands they live in. Because they are engaged in a variety of ecosystem processes, any disruption to these ecosystems, such as hunting or climate change, is first reflected in the otter populations in the area. For species conservation and management, a basic knowledge of species ecology is required. Feeding and habitat ecology are critical for species survival because they allow for informed decisions regarding the protection and management of a species' preferred habitats. Additionally, the Himalayan mountain ranges are anticipated to warm faster than the worldwide average. As a result, any animal found in this region, such as the otter, is of special significance. Future climatic changes are expected to have a disastrous effect on both the ecosystem of this area and the animals that occupy the environment. Himalaya is home to three otter species: Eurasiasn otter (Lutra lutra), Smooth-coated otter (Lutrogale perspicillata), and Small-clawed otter (Aonyx cinereus). Otter research in the Himalayan area has received less academic attention than other parts of the world, leading to a lack of scientific knowledge about the species and its ecosystem. In recent years, the conservation and scientific significance of otters in the Himalaya has grown significantly. However, several unknown aspects of this species have not been thoroughly investigated. Hence, this research aimed to address a knowledge gap on current distribution and future scenarios for otter species found in Himalaya. Determining the occurrence of rare and endangered species in freshwater habitats is critical for ecological research and conservation concerns, but it may be time consuming and difficult. In the present research we also tested an environmental DNA approach to detect Lutra lutra in the South Italian and Himalayan rivers. We used the recently proposed Climate Niche Factor Analysis (CNFA) framework combined with Species Distribution Models to assess the vulnerability of three otter species found in the Himalayan region, namely Aonyx cinereus, Lutra lutra, and Lutrogale perspicillata, to 2050 climate and land-use change. Our study revealed that future climate and land-use change will shrink (6–15%) and shift (10–18%) the geographic ranges of the three Himalayan species, with land-use changes having much more severe consequences than climate change. Among the vulnerability factors, sensitivity was more important than exposure in determining the otters' vulnerability. In contrast to the most generalist, L. lutra, the most specialised species, L. perspicillata, exhibited the greatest vulnerability. Our findings showed that combining climate and land-use change components in CCVAs may result in divergent estimates of species vulnerability when compared to methods that solely include climate change. Furthermore, intrinsic factors like species sensitivity were shown to be much more relevant in predicting vulnerability than extrinsic factors like habitat exposure. We also examined the ecological niche overlap, similarity, and potential distribution of the three otter species—L. lutra, A. cinereus, and L. perspicillata— throughout their ranges. We created potential distribution maps for three of four Asian otter species (Lutra lutra, Aonyx cinereus, and Lutrogale perspicillata) using SDM, as well as a comparison of their geographic and climatic niche overlap and similarity. According to our findings, L. lutra, L. perspicillata, and A. cinereus are appropriate for 77.48 percent (SD=10.19), 77.32 percent (SD=9.31), and 75.26 percent (SD=10.68) of the respective IUCN ranges. The L. lutra niche was the largest of the three species, with a core centred on high NDVI (of July), NPP, and Driest Quarter Precipitation values. The niches of the other two species are distributed along a gradient of NDVI (February), Annual Mean Temperature, Mean Temperature of Wettest Quarter, and Precipitation of Wettest Month, with the A. cinereus niche lying toward greater values of these predictors than the L. perspicillata niche. Significant niche similarities were found between A. cinereus and both L. lutra (D=0.40, p0.05) and L. perspicillata (D=0.56, p0.05) in niche similarity tests. Furthermore, substantial similarity was found between L. perspicillata and A. cinereus (D=0.56, p0.05), but not between L. perspicillata and L. lutra (D=0.31, p0.05). Finally, niche similarities between L. lutra and the other two species were not significant (with A. cinereus, D= 0.40, p0.05; with L. perspicillata, D= 0.31, p0.05). Two of the three species are now classified as Vulnerable on the IUCN red list due to an estimated population decrease of more than 30% in the past 30 years, while L. lutra's East Asian range is extremely fragmented and rare, as is the situation with many terrestrial mammals in South Asia. Despite being well adapted to human-threatened environments, each species' appropriate habitat only covers around 75% of its present range. Wetland loss, poaching, pollution, and a decrease in prey biomass are dangers to all the species. Our results indicate that stringent protection and freshwater habitat restoration may help them expand their existing range and expand their present regions of residence in Asia. In this thesis, we also evaluated the potential of utilising environmental DNA (eDNA) to detect the presence of Eurasian otters from South Italy. Environmental DNA (eDNA) detection may offer novel and reliable methods for monitoring and conservation of rare and elusive species like the Eurasian otter, Lutra lutra. We used an experimental approach based on a target qPCR assay to detect L. lutra eDNA from water samples as a rapid monitoring tool to complement fine-scale conventional field surveys on a broad scale. This is the first time in Italy that an eDNA-based method has been used to monitor the presence of L. lutra. We compared the eDNA-based findings to conventional survey observations and found that this novel method to large-scale monitoring of such secretive aquatic species is reliable. We also tested an environmental DNA method to detect Lutra lutra in Himalayan rivers. Little is known about the Eurasian otter's habitat preferences throughout the Himalaya, particularly in the Trans-Himalayan region. This indicates a major knowledge gap in the region's poorly-known species biology and conservation. Future climate change is expected to have devastating consequences for the ecosystem of Himalayan region as well as the species that occupy the terrain. The findings of eDNA monitoring methods revealed the presence of L. lutra eDNA in 11 out of 15 Himalaya samples tested positive, a rate of 73 percent compared to 53 percent using the conventional monitoring technique. The PCA biplot overlaid on the scatter plot revealed that absent locations had a large Channel width and low Nitrate, Acidity, Surface velocity, and relative humidity values. We used glmulti to test 2100 models by autoruning various combinations of variables. The variables that contributed to the top five GLM models explaining the occurrence of eDNA at the 15 sample locations were acidity, channel width, and surface velocity. The concentration of acidity (pH) was shown to be the most important factor in the presence of otters (AIC = 10.45). In this context, environmental DNA (eDNA) surveys may help to overcome the expenses and constraints of conventional monitoring techniques in terms of species detection. For the first time, our results demonstrated that non-invasive molecular monitoring methods may effectively detect the presence of Lutra lutra in freshwater bodies, particularly on a medium-large scale. However, when evaluating an area with just a few sampling sites or a limited number of repetitions, the use of the eDNA method to detect otter presence in water samples should be approached with care. Future research should focus on testing eDNA surveys in various seasons and environments, since eDNA detection may be affected by temperature and other environmental variables that contribute to DNA degradation.