Variability in habitat selection between herds for a widespread ungulate

Abstract

Understanding habitat selection is critical for the conservation of ungulate species. Our aim was to (1) quantify herd-specific habitat selection for American pronghorn (Antilocapra americana) in the southwestern United States and (2) produce a habitat suitability map that can aid in the prioritization of management actions. We used GPS telemetry locations for individual pronghorn from 2007–2013 representing six herds and remotely sensed habitat covariates to model habitat selection. To determine the effect of each habitat covariate on habitat selection, we fit integrated step selection functions (iSSFs) to the data for each pronghorn herd using a mixed-effects modeling framework. We included random effects of individual pronghorn to account for intra-specific variability in selection. We used the coefficient values from iSSFs to produce a habitat suitability map averaged across the six herds and then evaluated the predictions against data from independently tracked pronghorn herds. Our findings indicated that while there is between-herd variability in pronghorn habitat selection in northern Arizona, there were also some common relationships. All herds selected for areas with a greater proportion of grassland and shrubland, however the magnitude of that selection varied between herds. Most herds also selected areas with low topographic diversity and a lower proportion of developed land with different magnitudes of response between herds. The responses to these two covariates seem to be related to function responses to local limiting factors. The average habitat suitability map indicated large swaths of unsuitable area separating some herds with large areas of habitat in the northeast. Our results demonstrate the importance of investigating herd-level variation in habitat selection analyses for herd-forming species, meaning managers can make decisions that are tailored to a herd's unique situation but also contextualize those decisions within conservation efforts across the landscape.