Our driveway is a half-circle, black gravel on sand, that seems to be an irresistible draw to turtles ready to plant the next generation in the ground to grow.

Almost all that clamber up the backyard are eastern painted turtles. But most years bring at least one common snapping turtle, moss-backed and lumbering, like a throwback to prehistoric times.

One snapping turtle already was dug in at the other end of the driveway as I left for work Wednesday morning. That the turtles can manage to scoop out a hole in the pounded-down earth amazes me, even though they do have long claws and broad webbed feet that apparently work either for paddling or shoveling.

While the much smaller painted turtles usually manage only about five to seven eggs per nest, the snapping turtle can deposit as few as 15 or 25 to as many as 80 to 100; the average is 20 to 40.

Betsy Bloom/Daily News photos

Snapping turtles look ancient because they are — their family, Chelydridae, arose about 90 million years ago in what now is North America, according to a March-April 2012 Audubon magazine article by Ted Levine, “The Staying Power of Snapping Turtles.” They’ve remained basically unchanged in appearance. Though at one point they did spread to Eurasia as well, they disappeared there about 2 million years ago, he writes.

At about 35 pounds and 14 inches of shell for well-grown individuals, the common snapping turtles are among the largest of the freshwater turtles in North America, only outdone in size and weight by its cousin, the alligator snapping turtle found in the South.

They’re found in Canada from southern Alberta to Nova Scotia and as far south as central Texas.

Unlike a number of other turtles, snapping turtles can’t pull themselves completely into their shells, as the plate on their belly — called a plastron; the upper shell is the carapace — is small and leaves its limbs and underside relatively exposed, according to the Wisconsin Department of Natural Resources. They also have a long, though well scaled, tail that also can’t be tucked into the shell.

This would seem to make the snapping turtle fairly vulnerable as turtles go. But as a University of Michigan web site mildly put it, “Snapping turtles make up for this lack of body armor with an aggressive temperament.” That’s primarily when confronted, though, and they’re more than willing to swim away if allowed.

They will eat almost anything “that they can get their jaws around,” the museum site advises, including “a surprisingly large amount of aquatic vegetation.” One somewhat grisly feeding fact: they do kill other turtles, primarily by decapitation, though it’s not clear whether “this behavior might be territoriality towards other turtles,” the site admits, “or a very inefficient feeding behavior.”

They also eat mammals and birds, “although studies show that their reputation as a duckling predator has been greatly exaggerated,” the Wisconsin DNR site states.

As hatchlings, they will get preyed on by herons, raccoons, skunks, snakes, crows, even bullfrogs and largemouth bass. But if they can survive long enough to get big — up to 18 1/2 inches for the shell alone, not including the tail, which can be almost as long — they will have little to fear from other wildlife, the University of Michigan Museum of Zoology’s Animal Diversity Web site observed.

But they do have to fear us. The meat and eggs are considered tasty in some areas, but the biggest threat to snapping turtle are being hit by vehicles, usually as they cross roads to seek new accommodations or, if female, find a nest site.

Jim Harding, an adjunct wildlife specialist at the Michigan State University Museum, gave this advice for helping out even the intimidating snapping turtle should you come across one struggling to get across a road. (As always, don’t risk yourself in trying to assist the turtle.)

First, try to take the turtle in the direction it was headed, he said, “as long as the turtle’s chosen direction isn’t taking it into worse danger. There are times when turtles don’t choose their paths wisely, in which case I may take the turtle a little farther, away from the road.

“With snappers, it’s true, don’t lift by tail. Grabbing the rear of the shell is tricky, and the turtle will not appreciate that you are trying to help it. Thus for big snappers, I often opt to push them off the road with a stout sticky, or tease the turtle into biting an old towel or jacket and dragging it off the road as it hangs on.”

If it manages to avoid getting eaten when young or cracked open by vehicles when older, a common snapping turtle can live well into its 30s in the wild and into its 40s in captivity.

Hopefully the raccoons won’t find the nest site and we’ll have half-dollar-size hatchlings in about 80 to 90 days.

Betsy Bloom can be reached at 906-774-2772, ext. 240, or bbloom@ironmountaindailynews.com.