Turtle species across Ontario are facing increasing challenges to their survival. As roads and highways expand through their natural habitats, turtles are often forced to cross busy roadways to reach nesting sites. Unfortunately, many do not survive the journey.
Turtles are particularly vulnerable to population declines because of their unique life-history strategy. Many species take 10 to 20 years to reach sexual maturity and although females may lay hundreds of eggs throughout their lives, only a small fraction of hatchlings survive to adulthood. Research has shown that the loss of even a few reproductive females each year can cause populations to decline. Consequently, road mortality is considered one of the greatest threats facing freshwater turtles across North America.
Roads create more than just a collision risk. The sandy and gravelly shoulders of roadways provide attractive nesting habitat for female turtles because they are open, sunny, and easy to dig in. However, these roadside nesting areas expose adult females to the risk of being struck by vehicles, while eggs are vulnerable to predators such as raccoons, foxes, and skunks.
To counter the threats facing Ontario’s turtle populations, researchers and conservationists are exploring new ways to restore habitats and improve nesting success.
Exploring Alternatives
Traditional turtle habitat restoration projects have often involved constructing nesting mounds made of sand and gravel. While these mounds can attract nesting females and improve hatch success, they also have limitations. They require ongoing maintenance to prevent vegetation growth, require predator protection, and are not suitable in every landscape.
Researchers from the University of Waterloo and McMaster University have been exploring a different approach. Rather than building artificial sand mounds, Dr. Markle and colleagues investigated whether nesting habitats could be created within Ontario’s open rock barren ecosystems by mimicking natural nesting conditions.
Open rock barrens are unique landscapes characterized by exposed Canadian Shield bedrock mixed with wetlands and forests. Several turtle species naturally nest in small pockets of soil that accumulate in cracks and depressions within the rock. However, these nesting opportunities can be limited, causing turtles to seek alternative nesting locations along roadsides.
The study was conducted in a 660 hectare area located 10-15 kilometres east of Georgian Bay. The area supports four turtle species: Blanding’s turtle (Mooskadoons, Emydoidea blandingii), spotted turtle (Clemmys guttata), snapping turtle (Mikinaak, Chelydra serpentina), and midland painted turtle (Miskwaadesi, Chrysemys picta marginata).
Creating Rock Barren Nesting Habitat
The goal of the project was to create nesting habitats that closely resemble naturally occurring rock barren nests while providing stable moisture and temperature conditions for egg incubation.
Between May and June 2019, researchers constructed nine nesting sites on exposed bedrock. Each nest site consisted of a shallow soil-filled depression approximately 20 centimetres deep. To further replicate natural conditions, patches of lichen and moss were transplanted from nearby areas and placed over nesting sites. Three nesting treatments were created: lichen-covered nests, moss-covered nests, and nests containing a mixture of both.
The transplanted cover was expected to play a crucial role in regulating nest conditions. Moss and lichen help stabilize soil moisture, reduce erosion, and influence temperature fluctuations within the nest chamber. These factors are especially important because many turtle species have temperature-dependent sex determination, meaning incubation temperature influences whether hatchlings develop as males or females. Extreme temperatures can result in highly skewed sex ratios, which may threaten future population stability.
Monitoring Nest Performance
To determine whether the created nest sites successfully replicated natural conditions, researchers monitored both natural and constructed nesting sites over multiple years.
Researchers monitored turtle nesting activity during the 2019 and 2021 nesting seasons. Following the observation of a female turtle laying eggs in 2019, the nest was excavated and eggs were carefully measured and subsequently reburied in their original positions.
In 2021, researchers conducted a split-clutch experiment. Eggs from the same clutch were divided between natural nests and artificial nests, allowing researchers to directly compare hatching success under different nesting conditions while controlling for differences among species and individual females. Next, temperature and moisture sensors were installed within the nesting habitats to monitor environmental conditions experienced during egg incubation.
Additional monitoring focused on vegetation growth, soil composition, moisture retention, and hatchling success. Carbon dioxide exchange, an indicator of vegetation productivity and ecosystem health, was also measured at nest sites using specialized gas analysis equipment. Soil samples were collected to evaluate density, organic matter content, and porosity, all of which influence incubation conditions.
Exciting Findings
The results of the study were very encouraging.
Lichen transplants performed exceptionally well. Carbon dioxide exchange rates were similar between transplanted lichen patches and natural lichen communities during both wet and dry periods. This demonstrated that lichen can be successfully relocated while maintaining normal ecosystem function.
The moss transplants had variable success. Researchers believe that the moss experienced stress after being transplanted during a particularly dry period. Unlike moss, lichens become dormant during dry seasons and can recover quickly when moisture levels improve.
Most importantly, the created nest sites provided excellent incubation conditions for turtle eggs. In cooler years, the constructed nests maintained warmer temperatures and more stable moisture levels than natural nests, leading to higher hatching success. During warmer years, the nests prevent overheating while still maintaining suitable moisture conditions.
The created nest sites also exhibited lower soil density and higher porosity than many natural nests. These characteristics improved drainage and moisture regulation, helping create stable incubation environments. Previous research on sand nesting mounds has demonstrated the importance of temperature regulation, but this study highlighted the equally important role of moisture stability in promoting successful hatchling development.
New Habitats in Use
One of the most exciting discoveries occurred in 2021 when a Blanding’s turtle was observed nesting in one of the created lichen-covered sites.
This observation provided direct evidence that turtles are willing to adopt newly created nesting habitats when they are located along their natural travel routes. Although some turtle species return to the same nesting site each year, females are capable of selecting new nesting locations when suitable habitats are available.
Researchers also found that lichen-covered nests resisted vegetation growth more effectively than moss-dominated sites. Over five years, grass and sedge cover increased significantly across many sites, but lichen helped maintain the open conditions preferred by nesting turtles. This finding suggests that lichen may reduce the need for long-term maintenance of created nesting habitats.
Challenges and Future Considerations
Despite their success, created nesting habitats are not without challenges. One concern noted by the researchers is that concentrating nests within a small area could potentially attract predators. Previous research on communal nesting sites has produced mixed results, with some studies reporting reduced predation and others finding little effect. In this study, protective nest cages were used to minimize egg loss.
Climate change presents another challenge. Rising temperatures could alter incubation conditions and affect sex ratios in species with temperature-dependent sex determination. Wildfires, habitat loss, and changing vegetation communities may also influence the long-term effectiveness of nesting habitats.
Nevertheless, the study demonstrates that carefully designed nesting habitats can provide safe and effective alternatives to roadside nesting sites, particularly in rocky landscapes where natural nesting opportunities are limited.
Looking Ahead
While improving hatch success is an important conservation goal, researchers emphasize that protecting adult turtles remains essential for long-term population recovery. Created nesting habitat can increase the number of hatchlings entering the population, but these gains can be quickly lost if adult turtles continue to be killed on roads.
For this reason, conservation efforts must combine habitat restoration with road mortality mitigation measures such as exclusion fencing, wildlife underpasses, and ecopassages. These structures help prevent turtles from accessing dangerous roadways while maintaining connectivity between habitats.
The results of this study offer hope for Ontario’s turtles. By creating nesting habitats that closely mimic natural rock barren environments, researchers have demonstrated a practical way to increase nesting opportunities, improve hatching success, and encourage turtles to nest away from roads. Combined with continued efforts to reduce road mortality, innovative habitat restoration projects such as these may play a critical role in ensuring that Ontario’s turtle populations survive and thrive for generations to come.
To learn more about this research, visit: https://onlinelibrary.wiley.com/doi/10.1111/rec.14116
