Understanding Species–Habitat Associations: A Case Study with the World’s Bears

Abstract

Habitat modeling is one of the most common practices in ecology today, aimed at understanding complex associations between species and an array of environmental, bioclimatic, and anthropogenic factors. This review of studies of seven species of terrestrial bears (Ursidae) occupying four continents examines how habitat models have been employed, and the functionality of their predictions for management and conservation. Bear occurrence data have been obtained at the population level, as presence points (e.g., sign surveys or camera trapping), or as locations of individual radio-collared animals. Radio-collars provide greater insights into how bears interact with their environment and variability within populations; they are more commonly used in North America and Europe than in South America and Asia. Salient problematic issues apparent from this review included: biases in presence data; predictor variables being poor surrogates of actual behavioral drivers; predictor variables applied at a biologically inappropriate scale; and over-use of data repositories that tend to detach investigators from the species. In several cases, multiple models in the same area yielded different predictions; new presence data occurred outside the range of predicted suitable habitat; and future range projections, based on where bears presently exist, underestimated their adaptability. Findings here are likely relevant to other taxa.

Habitat occupancy of sloth bear Melursus ursinus in Chitwan National Park, Nepal

“…In the unprotected Trijuga forest area of Udaypur and Saptari districts, approximately 200km east of CNP, the probability of habitat use was estimated much lower at 43% (Pokharel et al, 2022). Variation in patterns of habitat use by sloth bears is a characteristic of most bear species; bears exhibit high diversity, complexity, and adaptability in their use of habitat mostly depending on the diversity and quantity of foods, and habitat conditions providing shelter and safety from human and non‐human predators like tigers (Garshelis, 2022). Species tend to exhibit occupancy–abundance relationships (Gaston et al, 2000; Zuckerberg et al, 2009), particularly in small and homogenous areas (Hui et al, 2009).…”

Forced sympatry? Spatiotemporal interactions of ursids, the Himalayan brown bear and the Asiatic black bear, along a gradient of anthropic disturbances in Western Himalaya

“…In summer, bears prefer sugar‐rich “soft mast,” which changes to fat‐rich “hard mast” in autumn (Manjrekar, 1989; Sathyakumar et al., 2013; Sathyakumar & Viswanath, 2003). The meat source they prefer is mainly small mammals and ungulates (Garshelis, 2022). In case of Himalayan brown bears, studies suggest the major part of their diet is composed of plant matter such as graminoids (sedges and grasses) (Nawaz, 2008; Penteriani & Melletti, 2020; Rathore, 2008).…”