Seasonal resource selection and migration of mule deer in an agricultural landscape

Abstract

Extensive agricultural development in the United States over the last century and subsequent restoration efforts through the Conservation Reserve Program (CRP) have led to many wildlife species occupying landscapes comprising a mix of natural and developed cover types. Understanding how species like mule deer (Odocoileus hemionus) move through and select resources in those landscapes is important for effectively managing populations and habitat. We examined seasonal resource selection, migration, and survival of female mule deer in the Columbia Plateau Ecoregion of southeastern Washington, USA, which is dominated by row-crop agriculture. We acquired global positioning system locations at 4-hour intervals from 57 adult females during 2018-2022. We used Migration Mapper 3.0 to detect migration, resource selection functions to evaluate resource selection, and Cox proportional hazards to quantify survival. Thirty percent of deer migrated for an average distance of 30 km each year. Residents and migrants had the same annual survival of 0.86 (SE = 0.03), similar to survival of adult female mule deer across their range. When selecting home ranges within the study area in summer and winter, CRP and grassland were the highest-ranked cover types, and selection for cereal agriculture and fallow fields was low to moderate. Within their home ranges, deer selected shrublands (including CRP) followed by tree-covered areas in summer. Cereal agriculture and fallow fields ranked lowest in summer, whereas grasslands and agriculture ranked highest in winter. Survival rates of residents and migrants were not related to their use of CRP or agriculture cover types. Mule deer used different components of the landscape mosaic seasonally, selecting vertical cover during summer fawn rearing and areas with young wheat and broad-leaved forbs during winter. Regardless of season and scale, intact (grassland and shrubland) or restored (CRP) cover types were most selected, demonstrating the importance of increasing both CRP and native cover for deer in agricultural landscapes.