Roadkill counts, 1937-2006, showed longterm decline
Tue, 26 Feb 2013 22:52:22 +0000
From ANIMAL PEOPLE, January/February 2013:
MENTOR, Ohio––Cathy Strah, a transportation department employee in Mentor, Ohio, from 1993 to mid-2006 logged all roadkills collected by city workers, forwarding her data sheets to ANIMAL PEOPLE. Her work, covering more than 5,000 animal deaths over twelve and a half years, was the longest-running all-species, year-round roadkill count known to ANIMAL PEOPLE.
Mentor, a city of just over 47,000 people, occupying 28 square miles, changed little during the years that Strah tallied roadkills––except that as the suburban tree cover matured, roadkills dropped precipitously.
Early in Strah’s survey there were sharp year-to-year fluctuations, from a high of 778 in 1995 down to 456 in 1996, rebounding to 668 in 1997. To that point, the five-year average was 622. The overall trend, however, was down, bottoming out at 301 in 2000 and 325 in 2001. After that, the highest tolls were 508 in 2002 and 439 in the last six months of 2005 plus the first six months of 2006.
The Strah data did not show any significant changes in the percentages of animals hit by species. Squirrels were fairly consistently about 25% of the total, raccoons about 20%, skunks about 12%, rabbits and opossums about 7-8%, and cats and non-migratory Canada geese around 4%. Deer remained around 1%. Dogs were well below 1%. When the totals rose and fell, they appeared to rise or fall in a consistent manner for prey, predators, and scavengers alike.
The Strah findings suggest a roadkill-per-driver ratio that gradually dropped from the vicinity of one per year per 50 drivers to about one per year per 62 drivers.
The Strah data may be compared in several respects to findings from a single-year survey of roadkills collected in 1937 by the highway department in Greenville County, North Carolina, reported in the May 1938 edition of The National Humane Review, published monthly by the American Humane Association from 1913 to 1976.
Greenville County, then largely rural, and Mentor, wholly suburban, occupy different climatic zones. Mentor had about as many licensed drivers in 1993-2006, circa 30,000, as Greenville County had human residents in 1937. Based on national norms, each Mentor driver drove about 10 times as many miles as the Greenville drivers did in 1937.
But the 180 miles of county highway in Greenville in 1937 compare well with the estimated miles of road from which the Mentor transportation department collected roadkill in 1993-2006. During 1937 the Greenville County highway department collected the remains of 524 animals, including 267 dogs, 93 cats, 34 rabbits, 17 chickens, 13 skunks, eight opossums, and one cow.
Reflecting the disappearance of stray dogs and free-roaming pet dogs from most of the U.S., the Greenville County drivers killed 10 times more dogs than were killed in Mentor during the duration of the Strah data collection. The Greenville County drivers also killed more cats than were killed in any four-year span in Mentor 1993-2006.
Altogether, about one driver in Greenville County per 17.5 killed an animal in 1937. Taking into account the difference in total miles driven, Greenville County drivers killed animals at around 30 times the rate of Mentor drivers in 1993-2006, even though few motor vehicles then traveled more rapidly than the typical pace of traffic today on an urban or suburban arterial street.