Exploring ecological separation between Himalayan blue sheep and Himalayan ibex during winter in Indian Trans-Himalaya

Abstract

According to resource selection theory, two related species with similar ecological requirements compete for the same resources. They can only coexist if they are ecologically separated, either by habitat or food preference. This study explored the resource use and ecological separation of ibex (Capra sibirica himalayanus) and blue sheep (Pseudois nayaur) during the winter in the Spiti Valley, focusing on their segregation in space, habitat use patterns, diet, and activity pattern. The study was conducted in Kibber and Chicham areas (57 km2) of Kibber Wildlife Sanctuary, Himachal Pradesh, India. This study slightly deviates from the findings of a previous study by Namgail (2006), which reveals a high overlap in the habitat use between ibex and blue sheep in the Zanskar mountains. Systematic sampling using transects and trails, vantage points, opportunistic sampling, and camera traps was employed. Habitat and vegetation variables were recorded at random points and animal sightings to understand the patterns of habitat use and food selection. Spatial and temporal overlaps were analysed and micro-histological analysis of faecal samples compared the proportions of monocots and dicots in their diets. The study investigated how ungulates utilize habitats and their dietary habits with the availability of resources in their environment. Results showed substantial overlap in activity patterns, with the Jaccard similarity index indicating less spatial overlap between the species. The generalized linear model and Non-metric dimensional analysis indicated segregation based on their habitat preferences. However, there were no significant differences in their diets, the two species differed in the use of habitat at finer scales. Ibex preferred interspersed rocky slopes and slabs because of high rocky areas (escape terrain) and sparse vegetation, trading food for security. Blue sheep preferred less rocky areas with high vegetation cover like smooth slopes. Ibex preferred areas with more escape routes available than blue sheep. Thus, I conclude that Blue sheep, being more abundant than ibex, occupy distinct regions within the study area, and have a competitive advantage. While ibex are present in smaller numbers and confined to a specific region. Understanding their ecological requirements, especially in harsh winters, is crucial for targeted conservation efforts to ensure the sustainability of these species in a rapidly changing environment. Future research should focus on climate change impacts on habitat use and resource availability