Road to Ruin: Tom Langen on Vehicles vs. Amphibians

It is remarkable how inured we have become to dead animals on highways. You don’t have to be behind the wheel of the responsible vehicle to see deer, skunk, raccoons and more that have been killed on our roads during their active seasons. To society at-large they are the collateral damage of our daily commutations.

Unnoticeable to the unwary eye, however, are the critters — frogs, salamanders, turtles, snakes and other smaller animals that die in even greater numbers. Amphibians are of special concern because of their habitat and movements.

A study conducted by Dr. Tom Langen,chair of biology at Clarkson University, his students and colleagues from nine other institutions concluded that roads cutting through amphibian habitat cause:

. . . direct mortality, behavioral barriers to movement, and reduction in the quality of roadside habitats. Our results suggest that the negative effects of roads on amphibians occur across broad geographic regions, affecting even common species, and they underscore the importance of developing effective strategies to mitigate the impacts of roads on amphibian populations.

The investigation used a “large-scale citizen science-generated database” to examine:

… the effects of habitat composition, road disturbance, and habitat split (i.e. the isolation of wetland from forest by intervening land use) on the distribution and richness of frogs and toads in the eastern and central United States. Undergraduates from nine biology and environmental science courses collated occupancy data and characterized landscape structure at 1617 sampling locations from the North American Amphibian Monitoring Program.

The study, Citizen science reveals widespread negative effects of roads on amphibian distributions, published in December 2014 in Volume 180 of Biological Conservation, was chosen by the editors as the edition’s must-read choice.

Student researcher Jessica Beach presents data on amphibian mortality and highways.

Student researcher Jessica Beach presents data on amphibian mortality and highways.

In an exchange of emails last December I asked Tom how prevalent was concern amongst conservationists about highway mortality. He wrote:

It is becoming apparent to conservation professionals that road mortality and disruption of habitat connectivity is causing declines and local extinctions of sensitive species whose populations are divided by roads. Salamanders are particularly prone to population declines due to roads – many species migrate from upland sites to vernal pools or other wetlands to breed, and these amphibians do not hesitate to enter roadways when they encounter them, are slow when crossing the roads, and take no evasive action to oncoming traffic. Segments of roads that are crossing points for migrating salamanders can be the site of mass deaths that result in rapid population declines, since all mature animals in a local population are likely to attempt to cross the road going to or returning from breeding.

Is road mortality preventable? First you must know the locations where animals move from one side of the road to the other – an area of study in which Tom specializes. Next, you need cooperation from highway agencies. In a future post we will examine successful strategies that provide small wildlife escape routes from vehicular traffic.