Don’t Let the Bugs Win!

What works and what doesn’t in the war against bugs?

Come May and June, it only takes a few minutes outside until you’re swatting those pesky bugs.

And along with this year’s early bug season comes the perennial discussion: What works against them? What doesn’t?

Well, I’m far from an expert on this, but I do occasionally use myself as an insect test lab and I check with folks to see what’s hot and what’s not.

Dr. Alan T. Eaton, the entomology specialist for the UNH Cooperative Extension, has put a lot of thought into products that attempt to offer relief from pesky insects.

While many describe themselves as insect repellents, that’s not exactly what they do, according to Eaton. They actually block receptors that mosquitoes, black flies and others use to find hosts for them to bite. By blocking the receptors, the products stop the insects from biting.

Some products, as you might imagine, are more effective than others. Eaton recommends that you check the active ingredient and always follow the label directions. 

Hair Shirts, Bear Grease and Bug Suits 

Before we get into the chemicals, how about the no-spray alternatives?

How about using nothing? No protection at all. Just go out there like a hair shirt and show the mosquitoes who’s boss.

I’ve hiked with folks who try this. Some just put up with the bugs and don’t complain at all. They wonder what the fuss is all about. I do wonder, however, whether they reach their vehicle at the end of a long, buggy hike, jump inside and in the privacy and comfort of their cars, let the profanities fly.

 hiked with a fellow from India a few years ago who’s only protection in one of the buggiest places in New Hampshire (Effingham) was a small fan, the size of a ping pong paddle. Seemed to work, but he was constantly swatting.

And I’ve often heard that Native Americans successfully used bear grease to keep away the bugs. While I wouldn’t ask for it at the drug store, I suppose you could get some bear grease if you tried hard enough. Then, if you did, what would you do? Rub it all over yourself? I suspect it would keep away more than the bugs.

Bug suits and hats are an attractive alternative, much less messy than bear grease. You can buy a top just for your head. You can get a shirt and top combo. Or you can get the whole suit -- pants and all -- and walk around like an astronaut.

They do work. I’ve used them in the woods and in the garden. But you can feel a little claustrophobic in there, sweating and squinting while the mass of flies hover around your head. 

DEET 

The champion of the chemical line-up seems to be DEET, the short name for N, N-diethyl-meta-toluamide. The stuff is as scary as its name, but it does seem to work against mosquitoes, black flies, midges and even ticks. It doesn’t work against deer flies and horseheads; nothing really fights them, according to Eaton.

Products with higher concentrations of DEET generally last longer and are more effective than those with low concentrations, Eaton says. But it shouldn’t be used in concentrations over 30 percent. And it should never be used on infants under 2 months old. And don’t get it in your mouth, nose or eyes.

The other problem with DEET is that it dissolves plastics, which invites all sorts of questions about its effect on your skin. 

Picaradin 

Products with picaradin are becoming more common, and like those with DEET, can come in pump sprays, aeresols and wipes.

On the plus side, picaradin doesn’t dissolve plastics, like cameras and such.

On the down side, picaradin seems to have a short span of effectiveness. I find I need to re-apply it every hour or so, unlike DEET. 

Cironella 

Derived from grasses native to tropical Asia, citronella is often used in candles and torches.

While I don’t recommend hiking with torches, they can be pretty cool near the campfire. 

Oil of Lemmon Eucalyptus 

According to Eaton, research has shown that natural products like this are less effective on mosquitoes than products with DEET or picaradin.

In my own decidedly unscientific tests with lemmon, eucalyptus oils and other naturals, I’ve returned from the woods, bitten and cranky. I wish they worked better than they do.

Some folks swear by the naturals. And that’s fine. I say, if it works by you, use it! 

Permethrin 

This isn’t a standard repellent. It’s really used as a treatment for clothing to ward off mosquitoes and other biting insects. I’ve found it works best against ticks, and it really does work.

It comes in aeresols, pump sprays and solutions. You generally treat the clothes according to instructions, let them dry and they’re good to go.

I’ve found the best bet for permethrin is to treat gaiters, boots and below-the-knees parts of a grungy pair of pants. That’s my anti-tick outfit. And it stays in the basement or on the porch.

Whatever ammo you choose against bugs, even if it’s bear grease, follow the label’s instructions and be flexible. If it doesn’t work, try something else.

Just don’t let the bugs win! 

Eric Aldrich writes from his home in Hancock.

Downtown to the Mountain on the Cranberry Meadow Pond Trail

Cheney Ave. meadow, Pack Monadnock in the distance.

Picture this for your next hike: You start in downtown Peterborough, fueling up with breakfast at Nonies, Aesop’s Tables or the Peterborough Diner.

Under a brilliant blue sky, you cross the Contoocook River and head up Pine Street and Cheney Avenue. Then you’re on the Cranberry Meadow Pond Trail, passing through a tranquil meadow, with Pack Monadnock, your destination in full view.

In 3 miles you’re on the Raymond Trail at Miller State Park. Go another 1.6 miles and you’re enjoying the view atop Pack.

“I love how much people are hiking the trail,” said Swift Corwin, the Peterborough forester who helped create the trail. “For many, it has been part of their daily routine.”

The idea of a town-to-mountain trail came to Corwin in pieces a few years ago. Landowner Cy Gregg had asked for Corwin’s help to build a streamside trail east of Old Street Road. At the time, Corwin didn’t think that it would be possible to connect downtown with the mountain because of sizable wetlands between the two. The idea sat on the back burner.

The Italian Connection

It took a trip to Italy to give Corwin the big picture.

“One day, we had this fabulous hike from the village of Schio up to the top of Mont Novegno,” he said. “It was Christmas and there were lots of people making this walk.  I just loved that you could go from town to the mountaintop.”

When he returned, Corwin learned that the people who had bought land around Cranberry Meadow Pond had protected the property with a conservation easement held by the Monadnock Conservancy and wanted to make their land available to hikers.

A look at the map convinced Corwin that a town-to-mountain trail would be possible.

“Thanks to the generosity and cooperation of the other landowners along the way, the path and the possibility unfolded,” he said.

This was in 2008, when the economy started to sour. The idea of a cool, low-cost, local hike actually gave the project a boost.

Blazing a Trail

Corwin and staff of the Monadnock Conservancy got to work. They scouted routes, cut brush, built bridges and eventually marked the trail with blue diamond blazes.

By building a boardwalk, the wetlands that once seemed like such a barrier became a nice feature of the trail.

Many volunteers have pitched in. More than a dozen seniors from Conval Regional High School recently worked on the trail, marking switchbacks, repairing and installing bridges and stepping stones, building a small boardwalk and installing benches by the pond. That session was leveraged by Eastern Mountain Sports, which agreed to fund the seniors’ class trip if they completed a day of community service.

“I think what I really like about the trail is the variety of landscapes it passes through,” said Emily Hague, the Monadnock Conservancy’s stewardship manager. “It really gives you a sampling, crossing a field, a wetland, a streamside hemlock grove, a pondside, a working forest, to the base of Pack.”

Access to Land

Hague credits the landowners who’ve generously agreed to host the trail. One landowner who completed a recent timber harvest also agreed to leave a buffer along the trail, demonstrating that well-managed woodlands and recreational hiking can be compatible.

Hague is also delighted that so many people are enjoying the trail. “Travelers from all over the country and the world write in our log book, and people walk the trail every day. It feels great to be able to provide this resource and to give people access to land that will always remain the way it is.”

Corwin knows that many hikers stop at the pond, enjoy the view, then turn back toward town. But continuing on towards pack, Corwin said, is worth the trip.

“The experience of being in town in the morning, walking through the village up Pine Street, across Cheney Avenue field, then across the boardwalk and into the deeper woods and on to the mountaintop and back is something that you won't forget.”

Eric Aldrich writes from his home in Hancock.

Two Guys’ Mission: Catch-M-All!

Clay Groves & Dave Kellam ... and yellow perch.

The sudden onset of spring has an amazing way of triggering a deep-rooted desire to fish.

That’s especially true for two guys named Dave and Clay.

Dave Kellam and Clay Groves are on a mission for fishin’. They’re determined to catch -- and eat -- every species of freshwater fish in New Hampshire. By their count, that’s 44 fish species in all, including the big, the small, the tasty and the not-so-tasty.

They had hoped to accomplish this impressive gastro-angling feat in 2011. But, a few of the species have turned out to be challenging to catch, so the adventure continues.

Dave and Clay met more than 10 years ago when they worked at Amoskeag Fishways in Manchester. Dave lives in Exeter and now works for an ocean planning group called SeaPlan and Clay lives in Conway and works for Lakes Region Community College. Though their work lives have parted, they still share a passion for fish and fishing.

Last year, they took their fishing skills to a new level with their quest.

Each Fish a Research Project

At the outset, Dave and Clay set out to catch all 48 species of freshwater fish as cited on an onlinelist kept by the N.H. Fish and Game Department. Then they learned that two are endangered: American brook lamprey and bridle shiner. Figuring it would be bad form to eat these (and also illegal) they were scratched from the Catch-M-All list. Another two are old records and may not occur in New Hampshire anymore, if they ever did: blacknose shiner and tadpole madtom.

That leaves 44 freshwater fish to catch and eat, which the two thought was a fair goal to pursue.

A mission like this begs for rules. The fish have to be caught legally, preferably with hook and line, but other innovations may apply. No nets or traps. They must eat the first legal example of the fish they catch. While they can catch the fish on their own, they must eat the fish as a team.

So far, they’ve caught and eaten 36 of the 44 species.

“This quest completely turns the typical fishing experience on its head,” Dave said. “Targeting each fish becomes its own research project.”

Clay enjoys the challenge of learning the habits and habitats of each species, then figuring out how to catch it with more or less traditional tackle.


“For most of the fish, we have to gear way down and use tiny hooks, about the size of the letter J in 12-point font size,” Clay said. “But it’s been a lot of fun and seems to resonate with a lot of people.

Eating each species presents another set of challenges. “We have to deal with fish that no one cares to eat,” Clay said. “And we can’t just fry every fish. We like to mix it up.”

Aquatic Superlatives

Many times the dynamic angling duo have been asked about the quest’s superlatives. So here are a few:

Smallest: a 1 ¾-inch-long mummichog, a notoriously hardy little fish that thrives in coastal or brackish waters. With mulled mummichog and egg nog, they made “chog nog” and served it to the apprehensive host of White Mountains Today TV show in North Conway.

Biggest: a 36-inch, 12-pound, 8-ounce Northern pike that Clay caught last month on the frozen Connecticut River in Hanover. It became the main ingredient in a maple blackberry pike jerkey.

Scariest: a margined madtom, a small catfish that’s native to the Appalachias and Eastern U.S., but not New Hampshire. They made a “margined madtom mousse,” a risky meal, considering the fish has a venomous gland near its pectoral spines. Fortunately, no one suffered margined madtom mousse malaise.

Biggest surprise: golden shiner, which they thought would taste terrible. After flipping a coin to see who would eat the head (Clay, as always), they fried the shiner. “It was fantastic!” Clay said.

Worst-tasting: slimy sculpin, a little bottom-dwelling and nocturnal fish. After catching it with worm and hook, they made “slimy sculpin scampi” and shared it with a reporter from N.H. Public Radio. Clay said that horrid meal ties with “pickled pickerel.” Though Eastern chain pickerel is a game fish and normally pretty pleasant, their preference of pickling the piscine proved problematic.

Hardest to catch: banded sunfish. After at least 10 trips intended for this little sunfish, their search continues.

And as the quest continues, so do Dave and Clay’s excellent adventures. Aside from their popular column in The Wire and the Mountain Ear, they’re working on a book and have pledged 10% of its profits to support the NH Fish and Game Nongame Program.

Wish them luck and follow their story at www.catch-m-all.com.

A Vision, a Mountain and a March 20 Deadline

Forest Society hopes to protect 390 acres on Mount Monadnock

More information at forestsociety.org/monadnock.

Amazing things happen when people identify an urgent need, express their vision and pull people together for action.

That’s exactly what happened in 1915 when visionary leaders from the Society for the Protection of New Hampshire Forests looked at the challenges facing Mount Monadnock. Seeing the potential that this treasured mountain could be irreversibly changed by development, they worked with scores of folks to protect 650 acres on its slopes.

It was a remarkable story in itself, and since then, the Forest Society has gradually protected some 4,100 acres on the mountain. These publicly accessible lands -- along with tracts conserved by the state and other organizations -- are arguably among the most treasured natural assets in the region, if not the state.

They did it tract by tract, piece by piece, and all with tremendous grassroots support.

Today’s Challenge

Now the mountain faces another challenge, another opportunity, where the Forest Society’s vision needs that grassroots support again.

The Forest Society is working to protect nearly 400 acres on Mount Monadnock and has until March 20 to raise funds to seal the deal. So far, the organization has raised a little more than half of the $760,000 needed.

If successful, the project will be the largest acreage protected on the mountain at one time since 1915.

“This is a real challenge,” said Dave Anderson, the Forest Society’s director of education. “It’s an incredible opportunity, but we have until March 20 to make it happen. And in this economy, we are working hard to raise the money.”


The Project in a Nutshell

The project involves two landowners, with tracts on opposite sides of the mountain.

In the northwestern corner of Jaffrey and a little bit in Marlborough, the Forest Society hopes to purchase 335 acres from the Stowell family. This tract includes a stretch of the Marlborough Trail, one of the mountain’s nicest trails and in the late 1800s it was one of the most popular routes to the summit.

Aside from excellent habitat for moose, black bear, bobcat and other mammals that require wide ranges, the piece has remarkable forests for forest-loving songbirds and many other species. It also holds some cultural resources, like the site of a former Shaker farm with links to Shirley, Mass. Remnants of the farm, established in 1793, can still be seen.

The Stowell family has owned the land for three generations and now needs to sell.

A Hand in the Future

On the southeastern end of the mountain, in Jaffrey, the Forest Society seeks to purchase a conservation easement on 55 acres owned by Charles and Ann Royce. Charles Royce is a former manager of Monadnock State Park and a longtime, tireless and passionate advocate for conserving the mountain.

Under the conservation easement, the Royce family would continue to own and manage the land. They could sell or transfer the tract, but the Forest Society’s easement would permanently protect the land and its natural resources.

“It’s about preserving the land as both a part of the natural view shed, but also ensuring that it is available to future generations,” Ann Royce told the Ledger-Transcript last fall. “The easement will be passed on to future owners of the property, with us having a hand in that future.”

The Royce tract also has important cultural resources, like home sites of some of Jaffrey’s early settlers and a road that was once the main road between Jaffrey and Keene.

March 20 Fast Approaching

Because of the urgency of the challenge and the importance of lands, the project has attracted some respectable support. Among the contributors so far are the Jessie B. Cox CLT - Cox Family Fund, the N.H. Land and Community Heritage Investment Program (for the Stowell tract), the N.H. Conservation Plate program, the Conservation Alliance and the town of Marlborough.

“We’ve raised $430,000 so far,” Anderson said. “We’re more than half-way there. But we’ve got a hard deadline of March 20 that’s fast approaching and an opportunity to do something that’s going to help protect the mountain for future generations. It’s an urgent appeal, but I’m hopeful we can do it.”

A plaque at the base of Monadnock’s White Dot Trail honors the vision of Forest Society leaders who helped protect the mountain, Philip Ayres and Allen Chamberlain: “…May it always remain as it is today. Free and wild and beautiful. The unspoiled heritage of the past. A haven of refuge for those who seek its peace in years to come.”

Amazing things can happen when people pull together.

To learn more about this project, visit forestsociety.org/monadnock.

Eric Aldrich writes from his home in Hancock.

Loverens Mill Cedar Swamp: Antrim’s Globally Rare Ecosystem

A boardwalk leads hikers into the cedar swamp.

Of all the ecosystems here in our region -- from hemlock forests to peatland bogs -- few are really rare.


But a swamp in the northern part of Antrim is globally rare.

Loverens Mill Cedar Swamp is a great example of what ecologists describe as an “inland Atlantic white cedar swamp.”

Because of its excellent condition, size and exemplary nature, The Nature Conservancy protected this place in 1999. In 2006, the Conservancy acquired an additional 635 acres that helped protect the swamp’s watershed.

Now, the Conservancy’s 1,200-acre Loverens Mill Cedar Swamp Preserve lies within a conserved landscape of some 15,000 acres, protected by the Society for the Protection of New Hampshire Forests and other partner organizations.

Thanks to volunteers and staff of The Nature Conservancy, a trail and boardwalk leads into a piece of this strange and quiet place. From the boardwalk, you can see that it’s really a type of forested wetland; dark, cool and damp. Nothing like any other place in the region.

New Hampshire’s Rare Wetlands

Of New Hampshire’s 500,000 acres of wetlands, only 1 percent are Atlantic cedar swamps. Most of them are small and near the coast. Some of those cedar swamps, like one in Kingston, is quite open in nature, with trees spaced far apart in bright sunlight.

Another good example is in Manchester -- also protected by The Nature Conservancy -- and is 42 acres. The Manchester swamp is a bit different from Loverens Mill. Manchester Cedar Swamp. It hosts ancient black gum (some 400-plus years old) and giant rhododendron, which flower in early summer.

At nearly 50 acres, Loverens Mill Cedar Swamp is New Hampshire’s second largest. And it has a few traits that give it a northern (or boreal) flavor. Surrounded by hills, the swamp sits in the bottom of a  bowl -- at 1,040 feet in elevation -- where cold air collects and influences the plants that grow here. You’ll see northern species like tamarack, black spruce, balsam fir and Labrador tea, among others.

Atlantic white cedars -- which are found along the Eastern coast from Mississippi to Maine -- grow extremely slowly. Botanists have found some Atlantic white cedars less than 1 foot tall that are over 200 years old. The old cedars in Antrim are a respectable 130 years old.

While Atlantic white cedars can grow on little hummocks in swamps, their collective success can hinge on the wetlands themselves. If drained or flooded, for example, cedars can die in the wetlands and the ecosystem would peter out. That’s what has happened throughout New Hampshire where cedar swamps were once more abundant.

The water levels at Antrim’s Loverens Mill Cedar Swamp has probably been fairly consistent for hundreds or more years. In fact, a study of pollen cored from the depths of the Antrim swamp show that cedar has been here for more than 4,000 years. That is quite a testament to this system’s resilience.

Guided Tour of Loverens Mill Cedar Swamp Feb. 25
On Saturday, Feb. 25, join botanist Nur Ritter and The Nature Conservancy’s Eric Aldrich for a tour of Loverens Mill Cedar Swamp. Meet at 9 a.m. at the preserve entrance, Loverens Mill Road, off Route 9 in Antrim. Hike wraps up by noon; co-sponsored by the Harris Center for Conservation Education.

Eric Aldrich writes from his home in Hancock.

Flying Squirrels: Our Amazing Gliding Rodent of the Woods

Flying Squirrels: Our Amazing Gliding Rodent of the Woods

It was around this time one year when we had enough snow to head out for a long, early-winter cross-country ski trek. At that sweet time when day starts fading into night, I noticed something moving in the trees, way up high. 

A squirrel, I thought, but too small for a red squirrel, and rushing perilously toward the tiny tip of a high limb. Then it jumped. 

This little guy stretched out his whole body, turning the flap of skin between his wrists and ankles into a sort-of sail or a kite. Like in slow motion, he glided gracefully to the next tree, landing near the trunk, 6 feet or so up from the ground.

Then it scurried up that oak, scooted way out on a high limb and jumped again to the base of another tree. It must have done this exercise a dozen times until it went out of sight. I saw that jumping from up high was the easy part. What really surprised me was the finesse and technique as it approached his landing tree. Just before landing, the squirrel could slow, turn and adjust, then raise his body as he approached the tree. He even seemed to use his tail like both a rudder and a parachute.

Opportunistic Little Fliers

That was my second introduction to the northern flying squirrel. The first was when our cat brought a live flying squirrel into the house, where it ran off and hid in the folds of a curtain until we convinced it to exit through the sliding glass doors. 

They are one of our more remarkable rodents, right up there with the beaver in a measure of awesomeness. 

To allow their flying habit, these squirrels are tiny, with an adult weighing in at little more than 2 ounces. Making them the paper airplane of the animal kingdom is the furry flap that extends between their arms and legs, called the patagium. Their flat tails can help them steer and land upright on a tree, instead of a humiliating face-plant.

Flying squirrels are nocturnal -- which is one reason they’re seldom seen -- and have big eyes that let them find food and avoid predators at night. 

They usually live in holes of trees or stumps, like those drilled or formerly occupied by woodpeckers. Their nests are often lined with any soft material they can find, including feathers, fur or moss. In the cold of winter, these nests can hold a bunch of notoriously social flying squirrels -- even more than a dozen -- all huddling and cuddling to stay warm. They’re not hibernators, so a few hardy souls will emerge on winter nights to seek food, bring it back and share it with the party.

Four flying squirrels feed off a beaver and deer carcass.

They’re opportunistic feeders, enjoying a menu that might include fungi, insects and their larvae, birds eggs, beechnuts and acorns, lichen and, yes, flesh. Here's a trail-camera photos of flying squirrels feeding off a beaver and deer carcass. (Right. I know. That’s another story.)

A Match-Making Squirrel 

When Michael Morrison was teaching science at Monadnock Regional High School in Swanzey, his students were faced with the riddle of what was stripping the bark off staghorn sumac twigs high off the ground. They set live traps baited with peanut butter, captured flying squirrels, and after some research learned that staghorn sumac is an important winter food source for flying squirrels.

Flying squirrels not only social animals, they’re known for their nurturing. Last year, when Nur Ritter of Hancock was doing a botanical inventory of forests in Wisconsin, one of the foresters he was with reached down into the base of a multi-stemmed tree and had a flying squirrel run up his arm. Turned out it was a nest with three young flying squirrels. The mother squirrel eventually relocated her litter while Nur and his crew were working.

One of my favorite stories about flying squirrels comes from my friend Chris Vincent in Vermont. Chris’s new friend was convinced she had a rat coming into her kitchen at night, so she called Chris to come and check it out. Chris brought over a little Have-A-Heart trap and reassured her that he’d catch the problematic rodent and release it unharmed. Over the course of a week as he tried to catch the critter, Chris and his new acquaintance got to know each other with dinner and movies. Finally, the trap captured the innocent flying squirrel and Chris released it safely. Thanks to that flying squirrel, Chris and his relieved friend have been a couple for 14 years!

Eric Aldrich writes from his home in Hancock.

Ice is Nice ... When It's Safe

Enjoy the ice, for God's sake! But make sure it's safe.

A few tips for staying safe on the ice

Depending on what the weather throws at us, late-fall/early-winter can be some of the best weeks to enjoy the ice.

In a lucky year, a week or so of snowless arctic cold can set up perfect ice-skating conditions.  It’s happened a few times in recent memory—when the ice is like a sheet of glass and you can slap a puck clear across the pond. Even better when you can see through the ice, fish and all.And all winter long, the ice can be great for ice-fishing, skiing, snowshoeing and all sorts of other fun things.

But fun on the ice comes with responsibility to make sure you’re safe on the ice. So, here are a few tips:

• Be patient/be safe. Wait for cold temps and safe ice thicknesses to set up before you venture out.
• Assume all ice is unsafe until you determine that it is safe. So, be prepared to check the ice thickness using an ice chisel or an auger.
• Check the thickness in several places and continue to check the farther you get from the shoreline. Remember that ice doesn’t form in uniform thickness across a water body. Currents from inlets, outlets, springs and channels can limit ice buildup. So, while the ice can be a foot thick across most of a pond, it could be a deadly 1 inch thick near an inlet.
• Ice conditions change constantly over the course of a winter. Warm spells can create slush, which then re-freezes and becomes weak. Heavy snow can create a layer of slush between the ice and snow, which can also make ice conditions weak and unpredictable.
• Beware of the ice near shorelines. Warmth from the shoreline can weaken or thaw ice on the edges, making it tricky to get off or on the ice.
• Watch out for tricky spots, like honeycombed, clear or squishy ice. These could be weak spots.
• Smaller ponds tend to set up sooner than rivers and large lakes, where currents and waves can keep ice from forming.
• Avoid gathering in large groups on the ice, especially in early winter.
• Don’t drive trucks or cars on the ice. The consequences can be humiliating and expensive, if not deadly.
• Don’t panic if you do fall through the ice. According to the N.H. Fish and Game Department, you should move back to where you fell in, where you know the ice was solid. Lay both arms on the unbroken ice and kick hard to climb back on. When you get back on the ice, roll away from the hole until you reach solid ice.  A pair of ice picks can save your life. Make them or buy them and keep them handy.
• Rules of thumb: According to the U.S. Army’s Cold Region Research Laboratory in Hanover, here are a few rules of thumb for safe ice: You should have at least 6 inches of hard ice for individual foot travel and 8 to 10 inches of hard ice for snowmobile or ATV.

A number of folks I know are skittish about the ice for one reason or another. Some have heard ice make those thunderous and wondrous cracking noises and assumed that sound means the ice is unsafe. Often, though, those are the sounds of ice thickening up, cracking as it expands. 

Once the ice sets up and you’ve determined it’s safe, get out there and enjoy it!