Abstract
A multi-stressor risk assessment was conducted at Yuma Proving Ground, Arizona, as a demonstration of
the Military Ecological Risk Assessment Framework. The focus of the assessment was a testing program
at Cibola Range, which involved an Apache Longbow helicopter firing Hellfire missiles at moving
targets, M60-A1 tanks. This paper focuses on the wildlife risk assessment for the helicopter overflight.
The primary stressors were sound and the view of the aircraft. Exposure to desert mule deer (Odocoileus
hemionus crooki) was quantified using Air Force sound contour programs NOISEMAP and MR_NMAP,
which gave very different results. Slant distance from helicopters to deer was also used as a measure of
exposure that integrated risk from sound and view of the aircraft. Exposure-response models for the
characterization of effects consisted of behavioral thresholds in sound exposure level or maximum sound
level units or slant distance. Available sound thresholds were limited for desert mule deer, but a
distribution of slant-distance thresholds was available for ungulates. The risk characterization used a
weight-of-evidence approach and concluded that risk to mule deer behavior from the Apache overflight is
uncertain, but that no risk to mule deer abundance and reproduction is expected.
