Amid drought, rise in roadkill in Sonoma County

California’s record-breaking drought is responsible for low reservoirs, dried-up creeks and parched, brown hillsides. But the most grisly toll can be seen on Sonoma County’s busiest roads: dead animals.

A growing number of animals are being struck by cars on roads in Sonoma County and other parts of California, according to university researchers and local agencies responsible for dealing with the mess.

The drought is driving animals closer to roadways and other populated areas in search of water, said Fraser Shilling, co-director of the Road Ecology Center at UC Davis. Roadsides often have more plant life than other areas due to rain runoff and nitrogen from car exhaust, which is necessary for plants to grow.

“That’s a bad thing,” Shilling said, “because it’s exactly where you don’t want animals to hang out.”

Shilling runs the California Roadkill Observation System, which has tracked wild animals killed on the state’s roads for six years. The data collection system relies on private citizens’ observations that are entered through an online system. It has tracked more than 300,000 cases of roadkill throughout the state and has shown an increase in large and small mammals, like deer and skunks; birds; and amphibians and reptiles since 2012, when the drought began.

This year, however, the number of large mammals like deer that have been killed on roads has mysteriously gone down. While this could be due to disease or other issues, Shilling said it also is possible that deer could have reached a “tipping point.” In other words, when there is a lengthy drought, animals that rely on open water sources might be decreasing in population because these sources are drying up.

Two agencies in Sonoma County that are responsible for picking up roadkill also have noticed the uptick in the grim toll of animals killed on local roads.

“The amount of wildlife we’ve been asked to respond to is at least double what we’ve seen in the past. And they’re much closer to urban boundaries,” said Steve McCaffrey, director of government affairs for Redwood Empire Disposal in Sonoma County.

The Ratto Group, the county’s dominant waste hauler and the parent company of Redwood Empire Disposal, collects dead animals on roads in unincorporated areas of the county and brings them to Sonoma County Animal Services under a contract with the county Department of Public Works.

“The easiest place to find (water) is in residential areas,” said Brian Whipple, operations manager of Sonoma County Animal Services. The agency does not track how many bodies of wild animals are delivered to its site, but Whipple said that he has seen more raccoons and skunks during times of low water.

In fact, data provided by Animal Services indicate that there has been an increased number of calls over the past two years to report roadkill such as foxes, skunks and opossums, and a decrease in the number of deer. In 2013, calls about dead animals were exclusively about deer, but so far this year almost 20 percent of calls have been about small mammals.

Some scientists, however, are hesitant to make a direct correlation between lack of water and animal-vehicle collisions on roads.

“You would have to enumerate how many animals were crossing the road, which is impossible,”

Nelson and his colleagues are no strangers to studying roadkill. They have been working to reduce the number of wild animals that are hit on Land Trust lands by building undercrossings, which provide ways for animals to bypass busy intersections like Highway 12 and Arnold Drive in Sonoma Valley.

Nelson said it is possible that more animals could be dying on roads while they seek out water, but there are other potential biological reasons for an increase. For example, during the fall, juveniles are leaving home for the first time and are not “as smart” as adults, he explained. They can end up in unfamiliar situations, like the middle of Glen Ellen, as they’re moving around to find their home ranges. Similarly, during rutting season in the spring, there usually are more deer hit on the roads as they seek out mates and ignore oncoming traffic.

Whatever the reason, there are some documented “hot spots” for wildlife vehicle collisions in Sonoma County, according to Shilling at the Road Ecology Center. In a report published this year, both state Highways 101 and 20 show high rates of collisions between Willits and Lake Mendocino, as does Highway 37 near the Petaluma Marsh.

“There’s no reason why (wild animals) would have adapted to fast-moving metal objects,” Shilling said. For humans to expect that animals will adapt to avoid traffic is “kind of like aliens who are surprised that we didn’t know how their spaceship worked,” he said.

By identifying hot spots and keeping track of roadkill, Shilling hopes to assist Caltrans and other entities in developing mitigation to protect both animals and drivers. Bridges or overcrossings and Sonoma Land Trust’s undercrossing are examples of ways to help.

However, the best way to have fewer animals killed on the roads, Shilling said, is for drivers to slow down.

You can reach Staff Writer Ariana Reguzzoni at 521-5205 or On Twitter @arianareg.

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