To counteract road-kill, a direct consequence of road-wildlife interactions, transportation planners and wildlife biologists are working together to find solutions. Historically, transportation planners have often placed wildlife crossing signs for deer and moose along roads where these animals may pose a traffic safety hazard. More recently, transportation planners are using wildlife crossing signs for smaller animals such as turtles where road-kill may pose a conservation issue. Wildlife crossing signs are commonly used because of their ease and low cost of deployment, however their effectiveness at reducing road-kill with small animals is unknown.
The overall objective for this study was to inform rigorous placement of turtle crossing signs inOntario, similar to previous research with deer crossing signs inAlberta,Canada; moose crossing signs inFinland, and camel crossing signs inSaudi Arabia. Rigorous and selective placement would improve the ability to measure sign effectiveness, improve sign recognition by motorists, and transportation planners, and also allow signs to behave as markers for more permanent and effective roadside mitigation, e.g. retro-fitted culverts.
We collected relevant information (design, theft and location) from crossing signs placed along roads (Highways, County and Township). We also used 1,293 records of dead-on-road turtle data compiled from various sources (most notably the Natural Heritage Information Centre, Bishops Mills Natural History Centre, and Ontario Amphibian and Reptile Atlas, Ontario Nature) to statistically analyse (Chi-square statistics) where dead-on-road turtles occur in relation to habitat and road type. We then compared whether turtle crossing signs were placed on roads where more dead-on-road turtles were found than expected by chance.
We outline the most pertinent results below:
- We obtained information for 469 turtle crossing signs, and georeferenced locations for 336 signs, 121 paired and 94 unpaired by conducting telephone, email and on-road driving surveys (Figure 1).
- We found that at least 27% of signs were stolen
- We found evidence for at least 10 different design types, however more than 96% of signs were of two types – the aerial flattened view adopted by the Turtle S.H.E.L.L. Tortue in 1998 and tortoise side view adopted by the Toronto Zoo – Adopt-A-Pond in 2009.
- On average turtle crossing signs were spanned approximately 1 km apart
- 19,000 km of the Ontario Road Network (Ontario Ministry of Natural Resources) bisected wetland-forest habitat (validated hotspots) where more dead-on-road turtles are expected to be found than by chance. Validated hotspots determined by habitat model published in peer-reviewed journal, North-west Journal of Zoology (2012).
- 13% of turtle crossing signs did not span a validated hotspot
- Dead-on-road turtles were found more often (p<0.05) on paved provincial highways and county roads
- 18% of turtle crossing signs were placed on gravel roads and 32% were placed on local roads where it was less likely to find dead-on-road turtles
From this study and supported by scientific literature, signs that are spaced at a meaningful distance (500 m), span turtle habitat (wetland-forest), and are placed on moderate to high volume roads would be located where turtle road mortality is greatest. In addition, selective and informed placement will increase recognition and awareness from motorists, and transportation planners. We also believe that a standardized design for a turtle crossing sign placed along roads with moderate to heavy traffic volumes would decrease sign theft because signs are less novel and it is less likely that thieves will go unnoticed.
Future work should focus on a more accurate and standardized inventory of turtle crossings signs. In addition, agencies that are involved with deploying turtle crossing signs should prioritize placement using the best available data and information, especially in light of the wide-spread threat of road mortality across the landscape. A co-ordinated regional response that focuses on information sharing and measuring sign effectiveness in an adaptive and rigorous approach will greatly improve the success of turtle crossings signs at reducing road mortality for Ontario’s declining turtle populations.
Please contact the authors for more information and look for an upcoming research article on this research in Ecological Restoration, Special Issue, December, 2012. Thank-you to the Ontario Ministry of Transportation for their financial support to complete this project.
Article appeared in the October edition of the Peterborough Field Naturalists’ newsletter “The Orchid”.
Kari E. Gunson, Eco-Kare International, 644 Bethune Street, Peterborough, Ontario, Canada, K9H 4A3, email@example.com
Frederick W. Schueler, Bishops Mills Natural History Centre, R.R. #2, Bishops Mills, Ontario, Canada, KOG 1T0, firstname.lastname@example.org