Turtles’ road to parenthood is paved with good intentions

It was late June, and an Environment Canada scientist was in Algonquin Park, looking for snapping turtle eggs as he studied effects of pollution on wildlife.

Snappers come ashore to bury their eggs in shallow holes, often in sand or gravel by a roadside. But the nests this biologist found were different.

They were buried in asphalt, in road patches so fresh the unmistakable smell of oil was everywhere.

And there were three nests, indicating three different mother turtles had gone to work in the same spot.

Asphalt contains some of the same oil-based pollutants that Environment Canada was studying. The department took a closer look, and its study is now published in a science journal called the Canadian Field-Naturalist.

Snappers are remarkably unpicky about where they will nest, the paper notes. They will lay eggs in farm fields, sand, clay, piles of wood chips, vegetable gardens, and even beaver lodges.

And now, asphalt. Specifically a type called cold patch, which is used for small repair jobs when it is not practical to bring in equipment to heat regular asphalt.

The nests were on the sloping side of a road south of Lake Opeongo away from traffic, and biologist Shane de Solla dug some eggs out of one of them.

Back at the Canada Centre for Inland Waters in Burlington, he exposed snapping turtle eggs to asphalt and then analyzed them. They soaked up toxins, in particular a common oil-based type called polyaromatic hydrocarbons (PAHs). They probably did not absorb enough to kill the turtle embryos, but deformity is another risk.

But why choose asphalt in the first place?

Snappers choose warm, sunny spots where the sun’s energy will warm the eggs, the paper says. But while they carefully select a site, they seem to have no sense of whether it is contaminated

Snapping turtles are Canada’s largest freshwater turtle, with a carapace (top shell) length of 20 to 36 centimetres and often weighing about 10 kilograms.