Sonoran pronghorn habitat use on landscapes disturbed by military activities

Abstract

The Sonoran pronghorn (Antilocapra americana sonoriensis) population in the United States declined to ≤33 animals in January 2003. Low population numbers and unstable recruitment are concerns for biologists managing this subspecies. We examined habitat use by pronghorn from 1999 to 2002 on a portion of the Barry M. Goldwater Range (BMGR) used for military exercises. We overlaid locations of pronghorn (n=1,203) on 377 1‐km2 blocks within the North (NTAC) and South Tactical Ranges (STAC), BMGR; we classified vegetation associations and disturbance status (e.g., airfields, targets, roads) for each block. Locations of pronghorn were distributed in proportion to vegetation associations on NTAC and STAC. Sightings of pronghorns were biased toward disturbed blocks, with 73% of locations of pronghorn occurring in proximity to mock airfields, high‐explosive hills (e.g., targets for live high‐explosive bombs and rockets), other targets, and roads. Disturbed landscapes on the BMGR may attract Sonoran pronghorn by creating favorable forage. Habitat manipulations simulating the effects of military disturbances on the landscape (e.g., improved forage) may improve remaining Sonoran pronghorn habitat.

Conservation‐reliant species and the future of conservation

“…For example, the recovery plan for the Sonoran pronghorn ( Antilocapra americana sonoriensis ) lists several management strategies that need to be “investigated” (USFWS 1998), so we did not categorize the species as conservation reliant. Some of these strategies are now being implemented as management actions (i.e., forage enhancement, supplemental watering, and captive breeding; Krausman et al 2005), and it is likely that such actions will need to continue to ensure the pronghorn's persistence. Our assessment of the extent of conservation reliance among listed species thus may underestimate the actual magnitude of the problem.…”

Biodiversity and the Heterogeneous Disturbance Regime on Military Training Lands

“…For example, the endangered grey hairgrass ( Corynephorus canescens ), a poor competitor which needs frequent ground disturbance for seedling establishment, thrives on active and recently abandoned military training areas in Germany (Jentsch & Beyschlag 2003). In North America, the endangered Sonoran pronghorn antelope ( Antilocapra americana sonoriensis ) exhibits a significant preference for high‐explosive target areas, presumably in response to increased productivity of grasses and forbs in those areas (Hervert et al 1997; Krausman et al 2005). In Hawaii, the Marine Corps has successfully doubled the population of the endangered black‐necked stilt ( Himantopus mexicanus knudseni ), in part by instituting annual maneuvers utilizing amphibious assault vehicles on mudflats (Drigot 2001; Rauzon & Drigot 2002).…”

Bombing and Sonoran Pronghorn: A Clear and Present Danger?

“…Others have discussed the influence of military activities on Sonoran pronghorn (Krausman et al 2004(Krausman et al , 2005. However, the effectiveness of the protocol to minimize injury or mortality on or near targets has not been addressed in the literature.…”

“…62% of the total United States population) used the tactical ranges at some point. The disturbance to the landscape from bombing may enhance the quality of the habitat by providing depressions that can contain water after rains and yield additional vegetation from water collection (Phelps 1981, deVos 1990, Hervert et al 2000, Krausman et al 2005.…”

“…It is likely that bombing activity alters Sonoran pronghorn habitat to enhance forage quality (Krausman et al 2005). However, because bomb sites are used by the Sonoran pronghorn (Krausman et al 2005), ordnance delivery poses a major threat to individuals. We recommend that the monitoring program continue as long as military ordnance is delivered to Sonoran pronghorn habitat.…”