The design of experimental studies of noise impacts on wildlife: Issues and outcomes

Abstract

Historically, most studies exposing terrestrial wildlife to anthropogenic noise experimentally have failed to prove biologically‐significant impact. These counter‐intuitive outcomes have given rise to political debate, fueled by marginal effects or weak trends in some studies that might have proved to be significant with better sampling procedures or controls. A number of recent studies have attempted to address these weaknesses by developing adequate sampling designs and balancing exposures with respect to important environmental factors (e.g., habitat type). Examples include studies of: (1) Effects of low‐flying NATO aircraft on Mexican spotted owl territory occupancy and reproduction; (2) effects of U.S. Marine Corps. helicopters on passerine reproductive success; (3) effects of operations on a U.S. Air Force bombing range on small mammal abundance; (4) impact of off‐highway vehicles on reproduction of northern goshawks in the Plumas National Forest; and (5) impact of Enduro motorcycle races on northern spotted owl physiology in the Mendocino National Forest. To date, preliminary outcomes of the studies suggest that more sophisticated models of effect should be developed, and additional research should focus on long‐term cumulative impact.