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In the U.S., deer/vehicle collisions cause 1.5 million motor vehicle accidents each year, resulting in 200 fatalities and over a billion dollars in property damage. With 1.75 million deer in Mississippi, deer/vehicle collisions are cause for concern. That's why an FWRC scientist, with lead collaborators from participating agencies, sought to better understand how deer respond to approaching vehicles before a collision occurs.
Dr. Ray Iglay, assistant professor in the Department of Wildlife, Fisheries and Aquaculture and FWRC researcher, was part of a team that evaluated deer responses to approaching vehicles.
The team conducted an opportunistic experiment protocol, recording observations of deer during a six-month period on the National Aeronautics and Space Administration (NASA) Neil Armstrong Test Facility (formerly Plum Brook Station) in Sandusky, Ohio. Observations took place on two lane roads with maximum speeds of 40 miles per hour. Anytime an observer saw a deer in the study area, they could start an observation to include in the study.
The researchers studied flight initiation distance (FID) or the distance from an approaching predator at which the prey flees. They were also interested in behavior associated with crossing the road.
"Flight initiation distance was one response we studied, trying to see at what distance from the vehicle would the deer start moving and initiating that flight or moving away from the threat. That movement could be going across the road or going back into the woods. The crossing the road behavior was also important to us. When they did have a flight initiation from the oncoming vehicle, did they cross the road or move away from the road?" Iglay said.
The team hypothesized animal proximity to the road and group size, speed of approaching vehicle, and environmental conditions as factors that might impact how quickly a deer responded to an oncoming automobile.
"We studied whether or not the deer had spatial and temporal thresholds of safety and the proximity to the road to see if and when the deer reacted," Iglay said.
The team recorded 328 vehicle approaches toward groups of an average of two deer. While the team found that proximity to the road influenced FID, deer didn't demonstrate spatial or temporal safety thresholds and FID wasn't impacted by either oncoming vehicle speed or environmental conditions.
"Deer responses were variable and did not demonstrate spatial or temporal margins of safety. While the findings supported that deer proximity to the road impacted FID, distance or speed of vehicle or environmental conditions had no apparent effect," Iglay explained.
The team also found that road crossing was influenced by group size and proximity to the road.
"Road-crossing behavior was slightly and positively influenced by group size during the winter. Deer also showed greater FIDs and likelihood of crossing when approached in the road, which indicated the direction of the approaching vehicle likely increased the perceived risk," Iglay said.
He said the research was an opportunity to discover more about deer/vehicle collisions.
"It's exciting to me to help with one piece of the puzzle in mitigating deer/vehicle collisions. The idea is that if we can accurately determine more about a deer's flight initiation distance, we might be able to design vehicles to be more threatening in order to initiate FID faster in the future."
Collaborators include Dr. Morgan Pfeiffer, Dr. Bradley Blackwell, and Mr. Thomas Seamans, U.S. Department of Agriculture, Animal and Plant Health Inspection Service (APHIS); Dr. Travis Devault, Savannah River Ecology Laboratory, University of Georgia; Wildlife Services, National Wildlife Research Center, and the Ohio Field Station. This research is funded by FWRC and U.S.D.A. Wildlife Services National Wildlife Research Center.
