Northern map turtles are at risk — but not on this eastern Ontario lake

The northern map turtle is considered a species at risk in Canada, but in at least one eastern Ontario lake they appear to be doing reasonably well.

In Canada, the turtles with their distinctive shells are only found in Ontario and Quebec, where they love open water and sunning themselves in groups on nearby rocks.

And while the turtle population on Opinicon Lake is doing “fairly well,” things aren’t perfect, said Grégory Bulté, a wildlife biologist at Carleton University.

“We’ve seen a pretty big increase in the number of what we call propeller injuries on these turtles in the last 20 years,” said Bulté, who has been studying and tracking the turtles on the North Frontenac lake since 2003.

Despite their relatively stable population numbers on the lake, 13 per cent of the female turtles have been struck by boats, he said.

It’s not just in the water they face danger, he added, noting they’re frequently hit by vehicles when crossing roads.

Several turtle species at risk

The northern map turtle is one of several species in the province that are facing or could face a decline in their population.

Others include the Blanding’s turtle, the eastern musk turtle and the snapping turtle (the latter two being considered of “special concern” in Ontario, rather than endangered).

Several things make map turtles distinctive, including their shell pattern, their social nature and the size discrepancy between males and females.

Not only do the turtles sun together, but they also spend winters hibernating together — and researchers like Bulté suspect their size differences may be reflective of that behaviour.

Female map turtles are more than double the size of their male counterparts, who aren’t territorial and don’t tend to fight each other.

That means flexing a larger shell isn’t necessarily an advantage males need, Bulté said — but it could be a benefit for females.

“The females are huge compared to the males,” he said. “[Males] don’t have an advantage of getting big, whereas females have that advantage because the bigger they are, the more eggs and the bigger eggs they can lay.”

Map shells

Because of their larger size, the females are sometimes mistaken for snapping turtles, but Bulté said spying a shorter tail is a good indication someone’s in the presence of the gentler reptile.

Another good indication is their “stunning” shells, said Bulté, on which an intricate network of yellow lines overlay the brown or olive-green background, giving the look of a topographic map.

The turtles also do their part to keep the population of the highly invasive zebra mussel under control, Bulté said, as they feast on them in lakes.

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