Roads, both big and small, pose a serious threat to wildlife all over the world. From deer and opossums to birds, insects, and turtles, we’ve all seen dead animals on roads. Try as we might to avoid hitting wildlife, most drivers have done it, often unknowingly. Of course we all feel guilty when it happens, but most roadkill isn’t really the driver’s fault. The number and location of roads, speed limits, and traffic volumes are the real problem, and roads aren’t generally built with the safety of wildlife in mind. In extreme cases, huge multi-lane highways are simply impassable barriers, permanently slicing wildlife populations into smaller and more isolated groups while causing the death of any animal trying to cross. The problem is getting worse, but all hope is not lost, and projects aimed at keeping wildlife off roads or to help animals cross safely are slowly gaining in popularity.
This forested overpass in Banff National Park allows large animals traveling great distances to cross safely over a major highway, with miles of fencing used to funnel large animals to the structure.
When most people think of a wildlife crossing structure they might picture a huge forested overpass used by elk, mountain lions, bear, and other large mammals because those are the projects that get the most press. While critically needed in many areas, wildlife overpasses built for large mammals moving vast distances are very expensive and often aren’t feasible due to logistical hurdles. There may never be enough overpasses to help smaller species across broad areas. Instead, large numbers of small scale projects upgrading existing structures to more wildlife-friendly designs are a more practical approach in many cases. A turtle, for example, is much more likely to be saved saved by a culvert upgrade or small underpass and some fencing than by a huge wildlife bridge.
Upgrading culverts to more wildlife friendly designs can also help people and saves money in the long run. This video outlines the many benefits that come with a culvert upgrade, including protecting the road and surrounding land from damage caused by floods. You can learn more here: Aquatic Organism Passage at Road & Stream Crossings
Turtles are threatened by roads more than most other species. As very headstrong animals, if a turtle chooses to cross a road, it might keep trying until it succeeds or is killed. Not known for their haste, the latter is a very likely outcome. Females looking for a place to nest are also attracted to roads because sunny roadsides resemble good nesting habitat. Wood Turtles are especially prone to being killed on roads due in part to the long distance they travel along and away from streams; streams that are often followed closely by roads. Wood Turtles may survive 80 or more years, and their populations depend on the long lifespan of adults, so their lives being cut tragically short on a road is a major loss to their populations. The early death of just a few Wood Turtles at a site each year can eventually wipe a population out.
These Wood Turtle bones were found under a guardrail next to one of the culverts being replaced are clear evidence of the threat highways pose to a this rare species.
In Vermont, where we started a Wood Turtle conservation program nearly five years ago, we are fortunate that the Vermont Agency of Transportation (VTrans) is enthusiastic about wildlife conservation projects. Like in any other state, our roads weren’t built with wildlife in mind, but VTrans proactively looks for opportunities to improve bridges and culverts to make them more friendly to wildlife. The agency also works closely with the Vermont Fish & Wildlife Department to identify the places where wildlife crossings, barriers, or other conservation approaches are needed most. Roads are still a major problem for wildlife in the state, and probably always will be, but it is encouraging to work in an area where the transportation agency is an eager partner in conservation. Recently, The Orianne Society began working with VTrans on a project that will keep Wood Turtles off a highway where roadkill has chipped away at their numbers for many years.
Perched culverts, which have a drop off and small waterfall on the downstream side, prevent fish from moving upstream and force turtles to cross over roads to get to the other side. Gradually, perched culverts are being replaced with more wildlife-friendly designs.
Al stretch of highway that passes through sensitive Wood Turtle habitat is due for culvert upgrades in the next few years. The existing “perched” culverts, which have a drop off on the downstream side, block the movement of fish and other aquatic animals from the main branch of the river upstream into tributaries. Those old culverts will be replaced with wider box culverts that will have flat, rocky, stream-like bottoms that allow turtles and other wildlife to pass through. At a couple sites, fencing will be installed on each side of the culverts to block turtles from crossing the road, with turn-arounds at each end to redirect turtles towards the stream. Replacing outdated perched and undersized culverts with wider structures is becoming commonplace in other states too, but proactively working with wildlife biologists to modify project designs and add extra accommodations for a rare turtle is going above and beyond.
This Wood Turtle was hit by a car and seriously injured in 2019, but survived due to medical intervention. Most turtles hit by cars are not so lucky.
To better understand how the old culverts affect how Wood Turtles use their habitat and to identify spots where additional barriers may be needed, we recently began a study using GPS transmittesr to monitor turtle movement patterns near select culverts. Through this work, we will learn how often and where Wood Turtles approach or cross the road, and we can document whether the new fencing is enough to redirect wandering turtles back to safety. The results of this study will help justify similar conservation projects later on and allow engineers to modify culvert and fencing designs to make future structures better at protecting turtles.
The data we collect from a Wood Turtle study will help us gauge whether upgraded culverts are used by turtles to cross under the road and may reveal additional locations where fencing is necessary.
To be clear, underpasses, overpasses, barrier fencing, and many other small scale projects meant to reduce roadkill help a lot, but they don’t “fix” the roadkill problem. New roads are still being built, others are being expanded, there is more traffic, and cars are driving faster. On a landscape scale, roadkill is getting worse, but there are a few things that we, the drivers, can also do to help.
Carpool to the greatest extent possible or use public transportation, work from home if you can, follow speed limits, and keep an eye open for small animals that could be mistaken for debris. Avoiding driving on rainy nights is also very helpful, especially in the spring when frogs and salamanders cross roads in massive numbers. Down the road, self-driving cars might play a big part in reducing wildlife collisions too, but roads will always pose a threat to wildlife, and anything we can do to make the problem a little less bad is worth the effort. In the case of Wood Turtles, a handful of culvert upgrades could be enough to save local populations in a stream from extinction, especially as other river valley habitat restoration programs gain traction. So, on a personal level, I am excited to work with VTrans over the next few years to make things a little bit easier for a population of Wood Turtles that really needs the help.