Wheat Vs. Wild: Habitat Selection, Migration, and Parturition of Mule Deer in an Agricultural Landscape

Rebekah A Hellesto

doi:10.7273/000005289

Converting wildlife habitat to agricultural monoculture is one of the greatest drivers of habitat loss and can be a severe threat to many wildlife species. However, because mule deer (Odocoileus hemionus) typically live in rugged, less arable landscapes, little is known about how they use habitat fragmented by agriculture. Using Global Positioning System (GPS) data from a partially migratory herd of 62 adult female mule deer from 2018-2022, we examined migration strategies and modeled habitat selection at three spatial scales in southeastern Washington, which is a mosaic of mostly privately owned cereal grain agriculture, shrubland, grassland, and restored cropland in the Conservation Reserve Program (CRP). A minority of the mule deer population was migratory (30%), with relatively short and fast migrations. During migration, they primarily selected for shrubland and grassland in both fall and spring. Mule deer used various components of the landscape throughout the year but selected grassland as their highest-ranked habitat year-round when selecting for home ranges within the study area (second order) and in winter when selecting habitat within their home ranges (third order). During summer, mule deer focused on shrubland and forested habitats within their home range, likely because it provided increased security and thermal cover for fawn-rearing. In the winter, they selected agricultural habitats to a greater degree, which might reflect the growing winter wheat (Triticum aestivum) providing more nutrition during that time. Survival from birth to recruitment into the adult population can greatly influence population dynamics of wild ungulates like mule deer and is affected by both nutrition and cover found in high-quality habitats. We used the GPS data from our population to create resource selection function models during parturition and early fawn-rearing and for fawn bed site characteristics (fourth order). We searched for fawns and fawn bed sites in 2021 and 2022 and used a parturition model to predict birthing events of collared females for which we were unable to find fawns in 2018-2022. For parturition, fawn-rearing habitat, and fawn bed sites, vegetation types that provided more vertical structure, including shrubs and trees, were consistently selected and agriculture avoided. Both intact (i.e., never plowed) shrubland and CRP shrubland were equally selected. These vegetation types provided vertical and horizontal concealment cover for fawns that were also important characteristics of fawn bed site selection. Our research suggests that to promote sustainable populations of mule deer in a landscape dominated by agriculture, managers and landowners could increase the prevalence of quality shrubs and trees where possible to improve habitat and continue support for the CRP program that provides economic incentive to restore croplands for the benefit of wildlife like mule deer.

Wheat Vs. Wild: Habitat Selection, Migration, and Parturition of Mule Deer in an Agricultural Landscape

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