Contrasting management paradigms for pronghorn in the arid Southwest and their northern range: a review

Abstract

Pronghorn (Antilocapra americana), a symbol of western North America, experienced diverging population trajectories since the mid‐twentieth century, with northern populations showing signs of recovery while those in the arid Southwest have struggled to persist. We conducted a systematic literature review of papers published through August 2023 to understand 3 questions. What are the habitat conditions needed for pronghorn to persist? What management actions can be taken to foster higher quality habitat? Do these actions differ for populations in the arid Southwest compared to their northern counterparts? Although the fundamental habitat requirements for pronghorn persistence have remained constant since the early 2000s, it has become clear that precipitation is a key factor influencing pronghorn populations in the arid Southwest. The precise mechanisms by which precipitation influences pronghorn population dynamics are not yet clear, whether through the availability of free water, by affecting forage quality, or indirectly via predator‐prey dynamics. Although range‐wide forage enhancement may be impractical, providing additional free water sources could facilitate greater movement, enabling pronghorn to access more and higher quality forage and areas with lower predation risk. To clarify how pronghorn persisted for thousands of years in this harsh environment, we must gain a better understanding of their historical metapopulation and migratory behaviors in the arid Southwest.

Climatically robust multiscale species distribution models to support pronghorn recovery in California

“…In the meantime, the niche reduction climate model also closely matched the historical distribution of the species, and evidence for a reduction in niche space is better supported in the literature (Bean et al., 2024; Brown et al., 2006). Both model outputs, and other analyses of the species' climatic niche (Bean et al., 2024) suggest that any future assisted reintroduction of pronghorn in California should source from other populations occupying more similar climatic conditions, such as in New Mexico or Texas or even from more arid‐adapted subspecies like Sonoran or Peninsular pronghorn to better match the current and future climate regime. A better understanding of the genetic stock within populations across the arid Southwest is needed to inform future reintroductions (Klimova et al., 2014; Lee et al., 1989; Stephen et al., 2005).…”

“…Winter migration in pronghorn is proximally triggered by cold temperatures and snowpack (e.g., Jakes et al., 2018), while historical summer migrations are hypothesize to have been triggered by heat and need for water (Bean et al., 2024). Therefore, we used only a small number of environmental predictors to capture these necessary migratory conditions for pronghorn.…”

“…We subsequently developed an expert‐driven habitat model, grounded in a comprehensive habitat suitability index (Cook & Irwin, 1985; Irwin & Cook, 1985) and a contemporary review of pronghorn literature (Bean et al., 2024). While the original habitat suitability index incorporated several measurements only available in situ (for instance, mean shrub canopy height), we adapted the basic model to accommodate the use of state‐wide GIS data (Figure 2).…”

“…However, in contrast with the American and peninsular subspecies, nearly all records of Sonoran pronghorn from GBIF were from post-1950. Sonoran pronghorn are a subspecies whose climatic niche aligns more closely with that of pronghorn in southern California (Bean et al, 2024) and therefore can provide important information about the climatic breadth of the species.…”

“…These challenges have been further complicated by a rapidly changing climate that is making pronghorn habitat in drier desert regions overall hotter and drier for longer portions of the year (Gedir et al, 2015;Seager et al, 2007). Pronghorn in desert states, where precipitation is a major driver of population dynamics, experience a summer bottleneck (Bean et al, 2024;Bender et al, 2013;Gedir et al, 2015). There is some evidence that pronghorn in desert states may be limited by access to free water, particularly postparturition (Bender & Rosas-Rosas, 2021;Morgart et al, 2005) and that individuals can suffer hyperthermia in extreme temperatures (Wilson & Krausman, 2008).…”