MILTON, Mass. (CBS Boston) – Sarah Kleinman’s regular Sunday hike in the Blue Hills certainly got her heart rate up. “I took a step and noticed right under me — probably a foot away — was the biggest snake I’d ever seen,” she tells WBZ-TV.

So the nurse midwife whipped out her cellphone and recorded the venomous, five-foot timber rattlesnake as it slithered across the trail. She was about half a mile from Chickatawbut Hill. “My first thought was that it must have escaped from the Franklin Park Zoo,” she says.

But when she shared her discovery with Mass Wildlife officials, she learned what many folks don’t know. Timber rattlers are native to all six New England states — but so rare these days they’re among the most endangered species in Massachusetts.

Five-foot timber rattlesnake spotted in Blue Hills Reservation (Image credit Sarah Kleinman)

In fact, after a century-and-a-half of decline, there are only a handful of pockets in the state where timber rattlers have been able to survive. And one of them is the 7,000-acre Blue Hills Reservation.

A pair of the snakes are even on display at the Blue Hills Trailside Museum — where they were rehabbed after suffering injuries in the wild. But the breed’s endangered status now makes it illegal to even disturb a timber rattler — much less catch or kill one.

“A lot of people seem to be really interested in this actually,” says Kleinman, who has been somewhat stunned by all the attention her sighting has received. “Mostly people who were just horrified that I even had this meeting with a snake. So I had a lot of validation for the fear I felt in the moment.”

It’s not widely known that two kinds of venomous snakes live here in Massachusetts — the other is the copperhead. While a bite from the rattler Kleinman encountered wouldn’t have been fatal, she’s still glad she didn’t step on it.

And as more and more people ask about her adventure, she’s been taking an informal poll. “Zero percent of the population likes snakes,” she tells WBZ.

Except for the experts at Mass Wildlife, who told her she was among the fortunate few in this region, who ever get to see a full-grown rattler up close. “I didn’t feel very lucky at first,” she says. “But now after a few days have passed — and because it’s such a unique sighting — I can embrace it a little bit more.”

In the figurative sense — of course.