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Tuesday, July 28, 2020

Pandemic upside: less roadkill

By TODD McLEISH/ecoRI News contributor

Photo by Will Collette
As automobile travel declined following stay-at-home orders during the first months of the coronavirus pandemic, so too did the vehicle-related mortality of the nation’s wildlife. 

Millions more animals than usual survived their often-treacherous attempts to cross roadways to reach breeding grounds and foraging habitat or to escape predators.

That is the conclusion of a study by scientists at the Road Ecology Center at the University of California, Davis. They found that 45 percent fewer wild animals were killed by vehicles in Maine compared to the previous month, and roadkill declined by 38 percent in Idaho and 21 percent in California during the same period.

The study noted that about 1 million wild creatures typically die on U.S. roads every day, so it’s likely that tens of millions escaped a crushing death. Most were probably small animals such as frogs, snakes, and salamanders for which road mortality is a leading cause of death, according to Fraser Shilling, the director of the Road Ecology Center.

But many large animals were spared as well. In California, for instance, the study found that 58 percent fewer mountain lions were killed by vehicles over a 10-week period beginning with the state’s stay-at-home order compared with the previous 10 weeks.

“This is the biggest conservation action that we’ve taken, possibly ever, certainly since the national parks were formed,” Shilling told The Atlantic. “There’s not a single other action that has saved that many animals.”

In Rhode Island, there is little data available to assess the impact of the pandemic on the road mortality of wildlife. But anecdotal evidence suggests that local animals have benefited.

Dylan Ferreira, a senior wildlife biologist for the Rhode Island Department of Environmental Management who monitors the state’s deer herd, believes there was a decrease in the number of deer struck by vehicles during the peak months when most Rhode Islanders were staying home.

“However, the majority of our road kills occur during the fall during the breeding season when deer are most active,” he said.

Scott Goodwin, the animal control officer in North Smithfield who disposes of an abundance of road-killed animals every year, observed far fewer dead animals on northern Rhode Island roads this spring.

“But it’s starting to pick up again now,” he said, noting that spring is usually a busy time for dead raccoons, skunks, and opossums because that’s when young ones are becoming active.

The only scientific effort underway in the Ocean State to assess the impact of reduced traffic on wildlife mortality is by a University of Rhode Island graduate student. Noah Hallisey has been studying road-killed reptiles and amphibians since last year. He said that during a normal year, road mortality is a serious problem for animals in the state.

“We have a lot of wildlife in Rhode Island and high road density and high traffic volume, so it’s probably a major contributor to population declines for certain species,” he said. “Amphibians and reptiles are especially susceptible because of their life history. They partake in mass migrations seasonally to breed and forage, and they often have to cross roads to do it.

“They’re also ectotherms, so they use roadways to bask and warm up. They’re also small and hard for drivers to see. And some drivers intentionally target them, especially snakes.”

Hallisey had been using a computer model to predict where and when large roadkill events may occur, based on environmental conditions — for example, most amphibians migrate at night when it rains — and the location of roads near wetlands. He then visited those areas at the appropriate times to see how many survived the crossing and how many were killed.

The pandemic forced him to reduce his research effort, but it also raised new questions about whether the stay-at-home orders would have an effect on the mortality of reptiles and amphibians. 

So he revisited some of the sites he documented last year as having high mortality, visited new sites this year, and plans to survey all the sites again next year to compare the ratio of live animals to dead ones.

“We were out one night at the end of April when more than half of the animals we found were alive, which is unusual,” he said. “I was amazed how quiet the roads were compared to what you would normally see.”

Although he hasn't yet completed his study, Hallisey believes there was a noticeable decrease in the number of amphibians killed by vehicles during the early days of the pandemic, but he didn't observe a similar decrease in reptile mortality.

“Given how many get killed, even a slight reduction in traffic can be a good thing for wildlife,” he said. “Even one less car on the road could save an animal.”

From the perspective of wildlife and road mortality, the timing of the pandemic couldn’t have been better. The large majority of reptile and amphibian movement occurs from March through June, the peak months of the pandemic lockdown. Many mammals and other animals are also especially active at that time as well.

“For those species that are breeding and moving around during those months, they definitely benefited from having fewer vehicles on the road,” Hallisey said.

Rhode Island resident and author Todd McLeish runs a wildlife blog.