Drivers of seasonal space use and movements of mule deer in agriculturally modified landscapes of the Great Plains.

Abstract

BACKGROUND: Understanding how key resources and anthropogenic disturbance influence animal space use and movement is essential for informing management of declining populations. Mule deer are studied extensively in mountainous and desert regions of North American. Yet, little is known about mule deer spatial ecology along the eastern periphery of their geographic range in prairie and agricultural landscapes in the Great Plains of Nebraska, where some populations appear to be declining. METHODS: We tracked 240 adult female mule deer with GPS telemetry to estimate seasonal home range size and movements in four study units in western Nebraska with highly variable natural and anthropogenic landscape characteristics. RESULTS: Females used smaller home ranges in areas with greater forage and woody cover and more evenly distributed habitat types. Females used larger home ranges with increasing croplands and human development in most study units but used smaller home ranges relative to these features within the unit with the lowest human presence. Migration between distinct summer and winter home ranges was rare (n = 18 females) and mostly involved relatively short distances (3–14 km). Interestingly, one female migrated approximately 100 km to establish a winter range in Wyoming before migrating back to her summer range in Nebraska. Migration occurred most frequently by females in the unit with the lowest proportion of croplands, whereas no females migrated in the unit with the most croplands, suggesting that abundant croplands may promote residency. CONCLUSIONS: Remaining natural habitat providing forage and cover is important to mule deer at the eastern periphery of their range in agriculturally modified landscapes. Agriculture provides costs and benefits to mule deer as it fragments the landscape resulting in larger home ranges, while also serving as a supplementary food source that likely contributed to the superior nutritional condition of mule deer in southwest Nebraska. Our work establishes the basic spatial ecology of mule deer in Nebraska and highlights the context specific nature of responses by ungulates to human landscape modification.