Turtles are ectothermic – or ‘cold-blooded’, which means that they cannot generate their own body heat, and rely on the environmental temperature for this; they warm themselves by basking in the sun. All ectotherms have a unique “preferred optimal temperature zone” that is essential for all their physiological mechanisms (moving, eating, mating- even their immune system depends on this temperature range!). Ectotherms cannot survive in very cold climates, and so are not found in the far north, and must hibernate in the winter in the south.
Turtles are on the move as soon as the weather starts to warm up in the spring. Usually the males are the first out and about – on their way to find mates, to find their ‘hangout’ spots for the spring and their favorite wetlands. As many males as females are found crossing roads, but their movement patterns tend to be spread out over the whole warm season. On the other hand, females are most frequently observed in June, during the height of their nesting season. See figure below, which shows the admission numbers to OTCC, of Blanding’s (top), snapping turtles (middle) and painted turtles (bottom). We recently published these findings in the journal Canadian Field Naturalist, and it is currently in press (Carstairs, Dupuis-Desourmeaux and Davy, 2018). Females are often found crossing roads to reach traditional nesting sites or laying eggs in the gravel along roads. Since there are roads on average every 1.5 km in Southern Ontario, and turtles can often travel many kilometers, they inevitably encounter roads in their travels. Turtle nests are laid in soil that is easy to dig and provides the correct amount of moisture so the eggs do not get too dry or too moist during incubation.
Incubation times vary depending on the weather conditions over the summer, but the eggs generally hatch in late summer or early fall. The gender of many turtles, including all of the species found in the Kawarthas, is determined by incubation temperatures. A long hot summer means that more of the young turtles will develop as females.
Less than one in a hundred turtle eggs laid will hatch and grow into an adult turtle. Unlike birds, turtles do not tend their nests once laid, nor care for their young once they hatch. Once the female has finished laying her eggs she never sees them again. Nests are easily found and destroyed by predators such as raccoons, skunks, foxes, and coyotes looking for an early summer meal. The babies that do hatch are vulnerable to predators on land and in the water and few ever reach maturity (8-25 years of age depending on the species).
However, adult turtles have few natural predators and enjoy a high survival rate. This high adult survival is essential for ensuring a healthy population. Most species live at least 30-40 years and some species can live to over 100 years! But it can take decades of nesting for just one egg to survive to replace the turtle that laid it. For instance, it has been estimated that it would take a snapping turtle 59 years to replace itself in the population! Turtles are very slow to mature, so often it can be 15-20 years before they even reach maturity.
All eight of the species of turtles in Ontario have been designated as Species at Risk. As is the case for many species at risk, habitat destruction has played a major role in the decline of turtles. Many of the marshes, swamps, bogs, and fens that turtles once called home have been drained, filled, or otherwise altered.
Roads have been built through several of the remaining wetlands, and as a result road mortality is now a major threat to turtles, second only to habitat loss. Other threats include illegal collection for food or the pet trade, boating mortality, and fishing bycatch.
We help to mitigate all of these threats. Our hospital helps to reverse some of the effects of road mortality, by returning turtles to the wild that would have been lost on the roads. In addition, our hatchling program augments this by returning babies hatched from the hospital patients, back to their mothers’ wetlands. Our field work adds to knowledge of turtle populations and also of the merits of ‘headstarting’ as a conservation strategy. Our education program addresses all threats, and teaches the public how to become stewards to help in the conservation of these vital members of our wetlands.
For more information on Ontario’s turtles, visit the Government of Ontario’s Species At Risk site, or Ontario Nature.