On weekdays, Tim Henderson is a computer repairman. Come the weekend, he’s a Waldron’s Warrior, part of an army of volunteers battling vandalism of Acadia hiking trails, and teaching people about the park’s unique stone trail markers known as Bates cairns.

Officially, Ellen Dohmen chairs the Bar Harbor appeals board and serves on the advisory board of Healthy Acadia. Unofficially, she’s the doyenne of Waldron’s Warriors, having trained Henderson of Castine, Dave Hollenbeck of Mount Desert, and a cadre of other caretakers of cairns along Acadia hiking trails.

During peak season, James Linnane works at a Bar Harbor Chamber of Commerce information booth. Off-peak, he climbs tough trails like Sargent East Cliffs, fixing cairns as he goes.

About 20 strong this year, the crew of volunteers is the brainchild of Charlie Jacobi, park natural resource specialist, who’s been working to stop the vandalism of Bates cairns, and random rock stacking that violates Leave No Trace® principles.

“It’s an ongoing battle,” said Jacobi, who first came up with the phrase Waldron’s Warriors in 2004, invoking the spirit of Waldron Bates, the Bar Harbor pathmaker who designed the cairns in the early 1900s, to recruit volunteers. “Warriors needed.”

But at times it seems like a losing battle, especially with increased visitation this Centennial year. And it’s not just Acadia that’s facing vandalism of historic and natural resources. A few weeks ago, Death Valley National Park’s iconic Racetrack was defaced by a vehicle that drove across the playa, creating tire tracks that may take years to disappear.

The only thing is to soldier on, and that’s what Waldron’s Warriors do.

Profiles in caring for cairns: Volunteers of Acadia hiking trails

Trained on the finer architectural points of the Bates cairn, Waldron’s Warriors fan out across Acadia hiking trails at least once every three weeks, but sometimes as often as twice a week, looking for cairns to fix or rebuild, and random rock piles to take down.

The cairns are built on two base columns of between 2 and 4 rocks, with a lintel stone, or platform, across the two columns and a pointer rock on top. The cairns help orient hikers and steer them in the right direction, while protecting the environment by keeping people on the trail.

Warriors spend hours at a time out in the field, usually during the shoulder seasons, but also in the summer, when the Friends of Acadia-funded Ridge Runners are also out caring for cairns and educating visitors.

Warriors adopt a series of trails, log hours and work done, and share the information with the park’s staff. They’re as passionate about their work, as they are about Acadia hiking trails. They have a faith in human nature, and believe education can help reduce the vandalism and rock-stacking.

Among the ranks of Waldron’s Warriors in years past: Nina “Cookie” Horner, co-chair of the Acadia Centennial Task Force; Moira O’Neill, candidate for state Senate, who is also selling “Anatomy of a Bates Cairn” T-shirts to help raise funds for the park; and Donald P. Lenahan, author of the 2010 book “The Memorials of Acadia National Park” and blog by the same name.

Here are some of the stories behind the current band of Waldron’s Warriors:

Ellen Dohmen – A retired pediatric nurse practitioner, she likes rocks, and giving back.

Not only is she one of the first Waldron’s Warriors, helping to train new recruits, she is author of “Rock Friends of Acadia,” which encourages kids and adults to use their imagination to see faces, animals and other shapes in the rocks of the park.

She’s also an Acadia Centennial Partner, helping to raise funds for the park; chair of the Bar Harbor appeals board; member of the advisory board of Healthy Acadia, an Ellsworth-based nonprofit; and volunteer executive administrator of Healthy Acadia’s “neighbor4neighbor” fund to help seniors in need.

For Dohmen, the worst parts of being a Waldron’s Warrior: Picking up after people’s dogs, and having to repair cairns that others purposely broke.

“The thing I don’t understand is the wanton destruction. I cannot understand what possesses somebody to do that. What was the attraction of doing that?” she said. “Periodically it frustrates you. I seem to be doing the same thing over and over again.”

But what makes up for it all, is the gratification of giving back, and educating visitors about Leave No Trace® and the meaning of the Bates cairns.

“Our job is not merely the cairn maintenance crew. That really understates the amount we do on the trail,” said Dohmen. “We really, really are ambassadors for the park.”

Her usual route, twice a week, is up Beachcroft Path and down Champlain North Ridge, trails practically in her backyard. “I’ve been working it so long, I don’t want it a mess. It’s pride of place.”

She also has Jordan Cliffs Trail this year, but wherever she’s hiking in Acadia, she has pride of place.

“Ultimately we own the park. Every single American owns the park,” Dohmen said. “I love to hike, I love the park, and I love giving back.”

Dave Hollenbeck – We ran into Hollenbeck last month as he was on his way down Sargent South Ridge Trail, looking like any other solo hiker. We got into a conversation and learned why he was out there, and that he’d been volunteering as a Waldron’s Warrior for about a year, under the tutelage of Ellen Dohmen.

He started his route that day by going up the Goat Trail and down the Norumbega Trail. Then he cut over to the Hadlock Brook Trail and climbed to the top of Sargent. Along the way he found “imposter cairns,” where people randomly stacked a bunch of rocks, as well as cairns where other people added additional rocks, or removed the top pointer stones.

Out there for hours, he hadn’t had lunch yet by the time we ran into him in the early afternoon. But he gave freely of his time, stopping for a photo by a Bates cairn, and answering questions about the best place to get a view of the natural rock formation known as the Amphitheater and why he volunteers.

“It’s a perfect way to be outside,” said Hollenbeck, a retired AT&T manager who’d moved to Mount Desert from New Jersey.

James Linnane – A chamber of commerce employee as well as a Friends of Acadia volunteer crew leader, Linnane became a Waldron’s Warrior about five years ago.

When he first found out about the group, Linnane thought it was a no-brainer. “What a deal – you get to volunteer, and you get to hike.”

Picking some of the steeper trails to be responsible for, Linnane has in the past done Sargent East Cliffs and Maple Spring trails. “That kind of hiking, I like.”

The other benefit of the tougher trails: Fewer people hike them, and there’s less messing around with the Bates cairns.

“Waldron’s Warriors are just people who love to hike. They’re really not looking for glory or badges,” Linnane said.

Tim Henderson – Among the damage Henderson has seen on the trails of Cadillac, his assigned territory: A lintel, or horizontal platform across the base stones, that’s been smashed and split in half; a messed-up cairn right next to a sign that tries to educate people about leaving the cairns alone; and random tall stacks of stones.

“It’s maliciously done,” said Henderson, owner of PC-fitness Computer Services of Castine. “Those are the things that really tick me off.”

A serious hiker, having just finished climbing all 67 New England mountains that are 4,000 feet and higher, and a fan of Acadia hiking trails since he was a kid growing up in Stonington, Henderson knows how critical cairns are in pointing the way.

“People don’t always hike in good weather,” he said. “Those cairns are like little beacons that are so important.”

A weekend Waldron’s Warrior for a year now, Henderson drives 1 hour 15 minutes from Castine to do his part in maintaining the Bates cairns, about once every couple of weeks. He sometimes does the trail work with his wife, Jennifer, with whom he also writes a blog, www.HikingMaineiacs.com.

Cadillac South Ridge, one of his trails, is one of the most used, and also one of the most vandalized.

“I could go down the trail, summit to Eagles Crag, turn around, and have to do it again. We’re talking within minutes. All the fake cairns – they just grow and multiply,” said Henderson. “It’s extremely frustrating.”

But the saving grace: “One of the best parts is getting to talk to people. I get to tell them what’s going on.”

And he proudly wears his Waldron’s Warrior baseball cap every time he’s hiking the trails, as a caretaker of cairns.

To volunteer with the park, as a Waldron’s Warrior or in any other way, contact the park’s volunteer coordinator Dianna McKeage, at (207) 288-8716, or via an an online contact form.