Slow-moving turtles are some of the most threatened wildlife in the province. Seven of Ontario’s eight species are at-risk, in large part due to roadkill. Most of the turtles found dead and injured on roads are females in search of nesting sites.
In southern Ontario, there are over 35,000 kilometres of roads. No matter where you stand, a road will be no more than 1.5 kilometers away. This is great if you are a driver, but not so great if you are a turtle.
Turtles like to nest in sandy soils found in sunny locations so that their eggs remain warm enough to hatch. Often, females will travel several kilometers and cross multiple roads to find suitable nesting sites.
What if turtles did not have to cross roads to find nesting sites? Would this reduce the number of adult females and hatchlings hit by cars? Would this also increase the number of turtles recruited into a population by improving the success of nests? Could artificial nesting mounds placed in safe locations reduce turtle mortality and increase population recruitment? In 2009, we initiated a research project to answer these questions.
To increase the likelihood of turtles finding and using artificial nesting mounds, conservation biologists need to predict the paths of female turtles and place multiple mounds along those paths. With help from Ontario Parks and the Algonquin Forestry Authority, we constructed four nesting mounds in safe locations in Algonquin Provincial Park. The mounds were made of sand and gravel, the same mix used on roadsides.
We hypothesized that artificial nesting mounds would be effective conservation tools for turtles because natural nesting sites, such as sandy beaches, are rare and artificial nesting mounds can mimic natural sites.
We tested three criteria that needed to be satisfied for the hypothesis to be supported:
Turtles have to be able to find the mounds and use them.
Hatching success has to be at least as high on artificial nesting mounds as at natural nest sites.
Nest conditions, including temperature, need to be similar to those at natural nest sites.
Female turtles were indeed able to find the artificial nesting mounds. We found four nests on the mounds, which was more than expected based on the area of the mounds relative to the area of natural nesting sites. Moreover, when we used observations of females walking from wetlands to natural nest sites to estimate paths females would need to take to encounter the mounds, we determined that females were actually unlikely to have walked across the mounds. This suggests that we could have increased the number of nests on mounds if we had placed them where females were more likely to encounter them.
We also found that hatching success and conditions in the artificial nesting mounds were equivalent to or improved from those found in natural nesting sites. We compared the hatching success of eggs laid in mounds with those in natural nests by carefully removing half the eggs found in clutches in natural nests and burying them in the mounds. Nest success was higher in the mounds (93 percent success rate) than in natural nests (56 percent success rate), and the incubation conditions, such as temperature, were the same in the mounds as they were at natural sites chosen by female turtles. This suggests that artificial nesting mounds can promote successful recruitment into a population by improving the success of nests.
Our research demonstrates that artificial nesting mounds – if properly placed – can reduce the negative impact of roads on turtle populations. Also, attracting females to artificial nesting mounds may increase nest success. It is exciting to consider how this simple and inexpensive intervention can help protect and restore at-risk turtles turtle populations in Ontario .
James Paterson is a PhD student at the University of Ottawa. His research focuses on the habitat selection, conservation biology and ecology of reptiles.
Dr. Jacqueline Litzgus is a professor at Laurentian University in Sudbury. Her research focuses on the application of scientific rigor to inform species-at-risk recovery. She has a deep affinity for turtles and snakes.
Guest blogger posting on Ontario Nature's blog about wild species and wild spaces. Together, we are the voice for nature in Ontario.