New study identifies roadkill hotspots in Sacramento region


A detailed inventory of animals killed on area roads has identified 22 areas in the Sacramento region where drivers are most likely to encounter wildlife crossing a roadway.

The release of the report on roadkill hotspots is considered a crucial tool to help drivers avoid possible fatal accidents and is being seen as a guide for scientists and agencies who seek to protect endangered species and other wildlife that cross roads and freeways.

The report, authored by Fraser Shilling of the UC Davis Road Ecology Center, culled volunteer observer reports of such incidents from 2009-2014 to establish where collisions between cars and animals were occurring.

The region’s hotspots include several points along Interstate 80 and and I-5. One is a stretch of I-80 over the Yolo Bypass where bird strikes are common.

Another is a stretch of I-80 where the freeway and Highway 49 converge in Auburn near the American River, “where there is no opportunity to go under the highway,” said Shilling, “so wildlife will go over it.”

Between April 1, 2010, and March 30, 2013, there were 365 crashes involving wildlife, livestock and other animals in the state Department of Transportation’s District 3, said Caltrans spokesman Mark Dinger. The district includes Sacramento and 11 Northern California counties, covering I-80 from Davis to the California/Nevada state line and I-5 from north of Stockton to north of Orland.

Statewide, Caltrans inventoried 3,126 reported collisions involving animals, Dinger said.

One human fatality in Sacramento County has been attributed to a wildlife collision since 2006.

Shilling said the roadkill report was compiled with the help of 1,100 volunteer observers throughout the state, including himself. The survey is the most extensive database documenting animal and vehicle collisions in California.

“Last year it seems like there has been an increase in rate of deer getting hit,” said Shilling. He said observation of deer hit by autos more than doubled last year.

He speculates that the drought may have something to do with it.

“They’re moving around more,” said Shilling. “They get moisture from vegetation, and they were probably having a hard time getting enough to eat.”

Despite the increase in deer mortality, roadkill observations overall have gone down slightly this year, said Shilling.

He believes the decline is not reflective of animals avoiding roadways. Instead he believes that roadways are decreasing wildlife populations, resulting in fewer roadkill observations.

The roadway hotspot with the most animal deaths is State Route 70 near Portola Valley. That stretch of road had 343 animals from 25 species killed in the roadway.

Shilling said that the numbers are deceptive, as the large majority of encounters between cars and animals go unreported.

The actual mortality on freeways and highways and streets is “much, much higher than this report represents,” said Doug Long, one the most prolific observers contributing to the database, with more than 3,000 roadkill observations logged since the effort began six years ago. Long is professor of ecology and biology at St. Mary’s College.

During a drive from Riverside to Oakland, Long used a special application on his phone to log 80 different species of roadkill he encountered on the drive. These include a wide variety of species – from snakes to birds, he said.

“You have to remember that the data points in the report have been collected by people (who) represent a very small fraction of all the people in California,” said Long.

Long said it is likely that 99 percent of encounters between wildlife and vehicles are never recorded.

From 1975 to 2005 there was a rise nationwide in people killed from collisions with animals, according to the Insurance Institute for Highway Safety. Deaths increased from 89 in 1975 to 223 in 2007, according to the institute. In 2013, deaths declined to 191.

“The roads can be seen as this one big superpredator that kills everything from salamander to elk,” said Long.

Long said collisions spike in summer and fall. The search for water during the drought may be a factor in the summer increase, but more research needs to be done to better understand roadkill hotspots, he said.

One species whose population has been directly affected by drought is the Pacific pond turtle – a species of concern in California, Long said.

This species lives in ponds and creeks that have been drying up, causing the turtles to walk on land in search of other aquatic areas, said Long. He said that observers in the Sacramento area and other regions have been seeing the turtles more often as roadkill.

The roadkill survey is seen as an important tool for drivers to know where problems may arise on roadways, and for policymakers and agencies, to suggest where work needs to be done to create pathways for wildlife to cross under roadways, said Sandra Jacobson, an expert in transportation ecology with the U.S. Wildlife Service Pacific Research station.

In some cases there has been so much mortality that roadways are responsible for wiping out most of a species in a given area, Jacobson said.

One species being impacted deeply by encounters with vehicles is the Pacific fisher, a cat-sized member of the weasel family. The species now exists only in small numbers in isolated pockets spread across a few areas of California. One small colony exists in the South Central Sierra region, south of Highway 41.

The fisher colony in the Sierra numbers just 200, said Shilling.

“If you kill one or two per year that’s a significant impact,” he said. “And that’s just the number of dead fishers we were able to find.”

Pathways for wildlife to cross freeways and other roadways exist in California, including a long culvert wildlife pathway under Highway 50 in the Sierra foothills built by Caltrans at a cost of $1.6 million. The agency builds roughly one pathway a year, a rate Shilling called woefully inadequate for a state as large as California.

“We have 12,000 miles of state highway in California, and we have another 100,000 miles of paved road,” said Shilling. “That’s a large and invasive road system. If we build only one structure per year it will take a few centuries to make a dent in roadkill.”

There are 11 wildlife crossing structures for large mammals in Caltrans District 3, said Suzy Melim, an environmental planner with Caltrans.

Building costs limit construction of wildlife crossings, Melim said. The cost of building a wildlife crossing on a new highway is roughly $200,000, compared with $2 million to add a crossing to an existing highway, she said.

Call The Bee’s Edward Ortiz, (916) 321-1071. Follow him on Twitter @edwardortiz.