Model-Based Assessment of Ungulate-Habitat Relationships
1. Understanding the influence of natural factors and anthropogenic impacts on populations of wild ungulates is of fundamental importance to their management. However, the spatial and observation processes involved in field studies often obscure our under
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Model-Based Assessment of Ungulate- Habitat Relationships
Abstract
1. Understanding the influence of natural factors and anthropogenic impacts on populations of wild ungulates is of fundamental importance to their management. However, the spatial and observation processes involved in field studies often obscure our understanding of the underlying ecological process, which is the real determinant of the distribution and abundance of ungulates. Modern hierarchical modeling approaches enable rigorous assessment of the influences of ecological, spatial and observation processes. In this chapter, using the models developed in Chap. 2, we investigate ungulate-habitat relationships in a tropical deciduous forest landscape in the Western Ghats, India. We confront the hierarchical spatial model with carefully gathered field survey data on ungulates as well as remotely-sensed data. 2. Our focus is on discerning the patterns of spatial variation in the density of five threatened tropical forest ungulate species. These study species differed in terms of body size, diet and social grouping behaviors. We hypothesized a priori, based on prior knowledge, the ecological determinants of the association between abundance and habitat characteristics for each species. These hypotheses were tested using our models. 3. We obtained count data on ungulates from 77 samplers (spatially replicated line transects) systematically placed with a random start. These transects covered an area of 1400 km2 spanning the study landscape. We used model-based analyses to investigate the influence of forest vegetation type, availability of palatable forage, topographic features, proximity to water, human disturbances and effectiveness of protection, on patterns of species abundances. We employed a Poisson-regression model under the class of Generalized Linear Mixed Models, within a Bayesian analytical framework. The models were confronted against survey data to assess the relative influence of hypothesized ecological determinants of abundance patterns. © The Editor(s) (if applicable) and The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2021 N. S. Kumar et al., Spatial Dynamics and Ecology of Large Ungulate Populations in Tropical Forests of India, https://doi.org/10.1007/978-981-15-6934-0_3
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3 Model-Based Assessment of Ungulate-Habitat Relationships
4. Our results showed that different predictor variables did influence each study species as we had hypothesized. However, the strength of inferences among these relationships varied. The patterns of ungulate abundance distributions generally reflected how local and landscape level influences met expected habitat requirements of each species. 5. For sambar, chital and wild pig, forest vegetation type mattered most. For gaur, a terrain feature (topography) was the most influential determinant of abundance patterns. Muntjac was most vulnerable to human disturbances. No single habitat covariate could alone adequately explain the abundance patterns of any of these speci
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