U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Enhancing the Perceived Threat of Vehicle Approach to Deer

Bradley F. Blackwell, USDA National Wildlife Research Center, Sandusky, OH
Thomas W. Seamans, USDA National Wildlife Research Center, Sandusky, OH

Document Type Article

Published in The Journal of Wildlife Management 73:1 (2009), pp. 128-135.


In North America and Europe, deer (Cervidae)–vehicle collisions (DVCs) are common and result not only in injury and death to the animals involved, but also human injury and property damage. Given that most DVCs occur during crepuscular periods, we questioned whether the perceived threat to deer posed by vehicle approach could be enhanced. We hypothesized that a vehicle-based lighting system that better complements peak visual capabilities of deer at night relative to standard tungsten-halogen (TH) lighting alone would elicit a greater flight-initiation distance (FID) by free-ranging white-tailed deer (Odocoileus virginianus). Our lighting system comprised 2 TH lamps and one Xenarc high-intensity discharge (HID) lamp. We defined an a priori logistic model comprising 4 variables potentially explaining deer FID relative to vehicle approach: 1) starting distance of the approach, 2) lighting treatment, 3) season, and 4) deer group size. Deer exposed to the combination of TH lamps and constant illumination of the HID lamp exhibited a mean (SD) FID of 136 (127) m. In contrast, deer exposed to TH lamps only initiated flight on average at 116 (127) m, and those exposed to the combination of TH lamps and the HID lamp pulsed at 2 Hz exhibited a mean FID of 89 (98) m. We contend that the pulsing of the HID lamp while TH lamps were illuminated resulted in consistent loss (over approx. 0.5-sec intervals) of a portion of the image on approach, possibly interfering with sensory information relative to the position of the potential threat. In contrast, the combination of TH lamps and constant illumination of the HID lamp contributed (P ¼ 0.033) to the probability of a FID ≥ 94 m. We suggest, therefore, that deer FID can be increased by combining currently available TH and HID lamps, or use of HID lamps alone, to enhance detection of an approaching vehicle at night. Also, we encourage research into new lamp designs to better complement deer visual capabilities as well as continued research to quantify deer FID in response to vehicle approach at night and lampspecific properties that can enhance deer detection of the vehicle.