It sounded like a chipmunk, or a squirrel, running in the brush beside him.

Then Dave Dunleavy looked down the trail he was running in Kent and saw no scurrying animal keeping pace with him.

What he’d heard was a rattlesnake, now in the trail in front of him, head raised and tail rattling.

Dunleavy — who lives in Kent, is my friend and, in another lifetime, was the environmental reporter for The Spe3ctrum’s sister paper, The News-Times — wisely stopped in his tracks and backed off.

Then, eager to get a better look, he took a step toward the snake.

“It started rattling like crazy,’’ he said. “And I thought ‘OK. Time to go.’ ”

Dave turned around and executed a double-time, full retreat. It was a case of Dave being at the right place at the right time to see one of the state’s most striking endangered species.

If you are going to cross paths with a timber rattlesnake in Connecticut, it is during these high weeks of summer, late June to August, when it will happen.

“The males are dispersing right now,” said Hank Gruner, vice president for programming at the Connecticut Science Center in Hartford, and a herpetologist who has studied the timber rattlesnakes in northwest Connecticut. “We just removed one in Macedonia State Park (in Kent) that was basking across from a residence there.”

At Kent School, the staff sees the occasional rattlesnake slide into view every year and is protective of them. This year, the number of sightings was up enough for wildlife experts from the state Department of Energy and Environmental Protection to come in and offer advice on how to make the school grounds less snake-friendly.

“They’ve seen rattlesnakes in plain view, which doesn’t usually happen,’’ said Jenny Dickson, a DEEP supervising wildlife biologist. “We don’t know why.’’

Dickson, who said the DEEP doesn’t have a fix on the number of rattlers in Connecticut, prefers to not get too specific about exactly where anyone would be seeing timber rattlesnakes in the state. That’s because the rattlers are endangered. And, as is often the case, rare means valuable.

“People can get $300 for a rattlesnake,” she said, referring to the illegal trade in the reptiles.

The snakes are endangered because they live in very specific habitat.

They need rocky ledge, the better to find a small cave, where they live in the winter in communal dens. But Gruner said they also need extensive forests surrounding those ledges. Those woods are home to the small rodents — mice, chipmunks, squirrels — the rattlers depend on for food.

Rattlesnakes were widespread throughout the state when the European colonists arrived. As people moved into rattlesnake habitat and made it over into human habitat — if they didn’t kill the snakes outright — the rattlers retreated into about 10 spots in northwest and central Connecticut.

The snakes have big, wedge-shaped heads, and, obviously, a rattle on their tail. In Connecticut, they either have dark crossbands mixed with yellow stripes, or a much darker color variation of shapes and stripes.

The DEEP website, ct.gov.deep, has good pictures of all the state’s snakes in its Natural Resources links.

The snakes also have two hollow fangs connected to venom glands. When they strike, the venom immobilizes the prey and the snakes get to swallow an unresisting, unwiggling meal.

When the snakes leave their communal den in spring, they tend to stay close to it, Gruner said.

As summer progresses, they move away to hunt. The males can glide off as far as a mile-and-a half from their dens and the females as much as three-quarters of a mile.

Because of all the Westerns we’ve seen, we tend to think of rattlesnakes as poison-spewing demons. But in fact, like copperheads — the other venomous snake in the state — rattlers are well-camouflaged and into conflict avoidance.

They only use their venom defensively when cornered.

“They’d rather move off into the woods,’’ Gruner said. “They only rattle when they’re confronted out in the open.”

Furthermore, most species wisely skedaddle when they see one coming.

“They are sort of used to being the biggest, baddest snake around,” Dickson said.

There are, very occasionally, records of copperheads and rattlesnakes biting people in Connecticut. In those cases, Dickson said, it’s human curiosity — maybe, even Darwin Prize stupidity — that accounts for the rush for anti-venom injections.

“It’s people reaching out to the snakes,” she said.

Reach Robert Miller at earthmattersrgm @gmail.com