Crossing boundaries in conservation: land ownership and habitat influence the occupancy of an at-risk small mammal

Abstract

Ecological research is critical for informing management of at-risk species, for example, by identifying what drives occupancy of species across landscapes. However, restricting research to public land and omitting private land, as commonly occurs in ecological research, can bias inferences because important drivers of population and community patterns may vary with land ownership. We conducted a landscape-scale study of a species of conservation concern, white-tailed prairie dog (WTPD; Cynomys leucurus), across multiple land ownerships in Wyoming. We quantified how WTPD occupancy varied with both land ownership and biotic and abiotic factors. We established a baseline occupancy rate for WTPD in Wyoming, and quantified how this baseline would have been biased if we had restricted our study to public land. We surveyed 440 sites throughout the Wyoming range of WTPD, which included sites on public (275), private (80), checkerboard (55), and Wind River Indian Reservation (30) land. We found that WTPD occupancy varied significantly with land ownership and elevation, with WTPD being four times as likely to occupy private as public land at the median study area elevation. This difference in occupancy may have been driven by variation in habitat quality between ownership types, but we could not definitively determine the underlying cause. Regardless of land ownership, WTPD occupancy increased with bare ground, but also when recent plant biomass (as estimated by NDVI) was higher than a site’s long-term average biomass. In other words, WTPD tended to occupy sparsely vegetated sites, but occupancy increased with short-term increases in biomass. The strong land ownership effect illustrates how study area delineation in relation to land ownership can influence research inferences and management actions, and why it is counterproductive to presuppose that certain land ownerships contain low-quality habitat. Ecologically, the variation in occupancy resulting from long-term site conditions, such as overall density of vegetation, relative to short-term site conditions, such as changes in plant biomass, can be used to improve long-term population monitoring for WTPD.