Early fawn-rearing habitat of mule deer in an agricultural landscape

Abstract

Survival from birth to recruitment into the adult population can greatly influence population dynamics of wild ungulates like mule deer. Fawn survival can respond to the quality of both food and cover, which can be modified by land-use practices, including agriculture and restoration of agricultural fields through the federal Conservation Reserve Program (CRP). We examined habitat features that influenced (1) fawn-rearing habitat by maternal females (e.g., 3 days before to 3 weeks after parturition), and (2) bed-site selection by mule deer fawns within a nearly 6000-km² agricultural landscape dominated by winter wheat in southeastern Washington, USA. We estimated the parturition date of 57 maternal females from fawn searches and a machine-learning parturition model. We used the females' GPS location during early fawn rearing to create a Resource Selection Function, and land cover measurements of bed sites for 47 fawns between 0 and 12 days old. Within their summer home ranges, maternal females selected shrubs and trees, vegetation types that provided more vertical structure, followed by grassland, with agricultural land cover, especially fallow, as the lowest ranked land cover type. Intact (i.e., never plowed) shrubland and grassland were higher ranked than were shrublands and grasslands restored through CRP. Likewise, fawns selected bed sites with greater overhead canopy cover and horizontal cover, especially when provided by woody shrubs and trees. Although 27% of bed sites were in growing wheat, agriculture was the lowest ranked land cover type in terms of selection. Our research suggests that populations of mule deer in landscapes dominated by cereal grain agriculture would benefit by (1) increasing the prevalence of quality shrubs and trees where possible to improve cover for neonates, and (2) supporting cropland restoration programs like CRP.