Understanding disease transmission in wildlife is contingent upon understanding the host species’ spatial use patterns. Resource availability across the landscape determines wildlife spatial use, and thus systems with highly variable resource availability can drive highly variable spatial use patterns. Consequently, resource availability can influence pathogen transmission in wildlife populations. Bighorn sheep (Ovis canadensis) have faced repeated spillover of the respiratory pathogen Mycoplasma ovipneumoniae from domestic livestock. Land managers model bighorn sheep seasonal spatial use and assign livestock grazing allotments based on areas where risk of contact with bighorn sheep is minimized. These models are built using data from Rocky Mountain bighorn sheep (O.c. canadensis) populations in Idaho, Oregon, and Washington. These areas are characterized by consistent seasonal precipitation and subsequent vegetation patterns, which in turn might reasonably drive consistent bighorn sheep spatial use. In contrast, desert bighorn sheep (O.c. nelsoni) live in more arid environments characterized by high annual variance in precipitation and vegetation availability. Given this, we hypothesized that desert bighorn sheep home ranges might exhibit high annual variation in response to local variance in precipitation. We examined this hypothesis by modeling seasonal home ranges over two years for six desert bighorn herds across southern Nevada. Local precipitation and vegetation availability varied among ranges as well as annually within herds, allowing us to compare how local precipitation regimes drive changes in home range within and across herds.
Results/Conclusions
Our preliminary findings suggest that seasonal home range spatial use increases inversely with precipitation. This trend is consistent across all seasons, as well as across all herds. One possible explanation for our results is that bighorn sheep exhaust forage in a patch quicker during years with less precipitation, and thus expand to new patches. We intend to incorporate these results into models assessing risk of contact with domestic livestock to revise the grazing allotment permitting in regions occupied by desert bighorn sheep. Our results will also be paired with camera trap and observed behavior data to further assess differences in M. ovipneumoniae transmission between Rocky Mountain and desert bighorn sheep.