Factors Influencing Seasonal Migrations of Pronghorn Across the Northern Sagebrush Steppe

Abstract

Globally, grassland systems have received the highest impacts from human activities, and therefore management of these systems is important for ungulate conservation. Pronghorn (Antilocapra americana) undertake seasonal migrations to satisfy annual life history requirements. The effects from environmental gradients and anthropogenic factors on pronghorn migrations are not well understood. My objectives were to: 1) Classify and determine metrics for various movement behaviors and states across individuals; 2) Predict multi-scale seasonal pronghorn migration pathways across the Northern Sagebrush Steppe
(NSS) and integrate scales into one spatial prediction and; 3) Create pronghorn connectivity network maps across the NSS. Based on 170 animal years from collared females, 55% of individuals undertook seasonal migrations. Using between-class analysis of metrics, three distinct movement groupings were identified. Next, I modelled multi-scale migratory pathway selection in response to anthropogenic and environmental parameters. Generally, migratory pronghorn selected grasslands, intermediate slopes and south-facing aspects and avoided increased well and road densities. Pronghorn selected stopover sites with higher forage productivity values and lower well densities versus migratory pathways. I then used a scale-integrated mapping approach and found that these spatial predictions performed as well or better than single order scales to predict migration pathways. Finally, using a suite of novel approaches, I created seasonal pronghorn connectivity networks across the NSS. I concluded that multi-scale migration followed hierarchically nested theory where finer scale decisions are conditional on broader scales that can be assessed sequentially. I suggest that the pronghorn is a broad-scale focal species useful for conservation planning across the NSS.