What is the value of habitat? Estimating the marginal contribution of habitats to carrying capacity – a case study of corsac and red foxes in Mongolia

Habitat loss represents a conservation concern for many species, especially those in central Asia, a region experiencing rapid economic growth and development. Managing habitat loss requires information on the relative value... [ view full abstract ]

Habitat loss represents a conservation concern for many species, especially those in central Asia, a region experiencing rapid economic growth and development. Managing habitat loss requires information on the relative value of habitats and how they contribute to supporting a population. However, this information is often challenging to obtain, which makes prioritizing conservation efforts difficult. We examined the value of habitats for two carnivore species, the corsac fox and red fox, in a steppe region of Mongolia. We addressed the question: what is the relative, marginal contribution of individual habitats to supporting the population of each species? Our approach involved building models that described how habitat amounts predicted occupancy probability in the landscape. We used models to map distributions, then applied a graphical technique called maximum clique analysis to estimate carrying capacity. Clique analysis estimated the maximum number of non-overlapping home ranges that could fit into a given map of distribution. To estimate the marginal contribution of habitats, we removed a given habitat in the landscape, then re-mapped distribution and re-ran the clique analysis. The marginal contribution represented the difference between carrying capacity with all habitats minus carrying capacity estimated without that particular habitat. Corsac fox occupancy was best explained by the additive combination of the amount of shrubland, open plains, tall vegetation, and rocky outcrops. Red fox occupancy was best explained by the additive combination of rocky outcrops and shrublands. Carrying capacity was 177 corsac foxes (83±7 SE females, 94±6 SE males) and 216 red foxes (123±6 SE females, 93±5 SE males) based on average home range sizes obtained through radio-telemetry. For corsacs, shrubland contributed the most to total carrying capacity, followed by open plains, tall vegetation, and rocky outcrop. For red foxes, rocky habitat contributed the most to carrying capacity. Our approach provides a framework for estimating carrying capacity based on commonly collected field data and could be applied to other territorial species over broad landscapes. Our results also provide a measure of the ecosystem service provided by each habitat in supporting a larger population and a quantitative basis for setting habitat conservation priorities.