Habitat characteristics along spring migration routes of elk, mule deer, and pronghorn in the southern San Juan Mountains

Abstract Conservation of migratory ungulate populations requires collaborative, large‐scale planning efforts that identify critical spatial components, habitat conditions, and resources necessary to support migratory populations. Yet our understanding of large herbivore migration ecology is limited for the southwestern United States, particularly in New Mexico. We assessed habitat characteristics within population‐level spring migration routes, stopover sites, and available reference locations for adult female elk ( Cervus canadensis ), mule deer ( Odocoileus hemionus ), and pronghorn ( Antilocapra americana ) from migratory herds in the southern San Juan Mountains in 2021–2022. Spring stopover sites for elk were characterized by taller browse and tree canopy heights compared to their migratory routes. Additionally, elk migration route habitats had minimal coarse woody debris and open understory compared to available reference locations. Although elk migration routes experienced a 48.5% higher overall extent of vegetation green‐up during spring migration periods (i.e., cumulative sum of the instantaneous rate of green‐up values) relative to available reference locations, the overall low values across site types suggest green‐up was low to moderate. Mule deer spring stopover sites were characterized by relatively flat terrain compared to their migration routes, which were located on ridgelines with sparse grass cover and were closer to agricultural areas compared to available reference locations. Relative to spring migration routes, stopover sites of pronghorn were defined by lower tree canopy heights and tree canopy cover, reduced cover and height of browse, lower understory cover, and more heterogeneous understory vegetation. In contrast to available reference locations, pronghorn migration routes had 70% lower instantaneous rate of green‐up values during the spring migration period and were located farther from mixed conifer forests. Additionally, aspen ( Populus tremuloides ) forests were found within pronghorn migration routes and stopover locations, although distances to aspen did not differ among site types. Our results can aid in directing habitat enhancement efforts toward migratory routes and stopover sites, facilitating the prioritization of management actions in areas with limited financial resources and competing land uses.