Monday, February 27, 2012

I spent the weekend in the heart of the White Mountains, which, unlike the river valley where I live, were as white as their name implies. There was a big snowstorm on Friday night that dumped several feet of snow on the region, and driving over the pass on the Kancamangus Highway as the sun rose on Saturday morning was the best feeling I've experienced in a long time. I love mountains. It doesn't matter if they are Appalachian or Rocky: I love the cleansing air, the aura of majesty they impart, the sense of adventure and solitude. I lived in my snow gear for 48 hours, throwing myself into the snow, impervious to its cold, soaking up the season.

When I was growing up in western Massachusetts, winter was all slush and dirty piles of snow on the roadsides. Then I moved to Vermont and it became an adventure, a reason to carry extra clothes and a shovel and kitty litter in your trunk, a reason to chop wood in the fall, to hunker down by a fire while snow falls outside, to discover the tracks of weasels and hares, to get outside and play in a clean, hushed world of bright skies and glittering ice. The year I spent without winter in the Marshall Islands left me out of whack, imbalanced without the season of rest and contemplation. I realized how much I love this season, how breathtaking it is in its own stark, silent way. Even when I was in Hawaii, I couldn't wait to get back to a cold New England winter.

And now I'm back, and it's been miserable, all drab brown landscapes and unseasonably mild temperatures. Ski resorts and outdoor enthusiasts are suffering. I wondered what effect the lack of snow has been having on the natural world. Here's what I found out. Reprinted with permission from the Valley News.

'Warm Winter Has Wildlife, People Both Befuddled'

Farmer Chuck Wooster, picking a tick off his dog in February, worries about the insects he might find in his vegetable beds this spring. Tramping through the brown woods, Lyme bear expert Ben Kilham finds male black bears happily feeding on beechnuts long after they’ve usually settled into winter dens. And birders across the region sit at their windows and puzzle over their empty birdfeeders.

Despite yesterday's snowfall, this year’s mild winter has been perplexing humans and animals alike. Some species, like white-tailed deer, fare favorably in warm temperatures and minimal snow cover. For other species like voles and snowshoe hares, the unseasonable winter can be detrimental, or even fatal.

But biologists agree that though the weather has been weird, it’s not unheard of. Plants and animals evolve over the course of hundreds of winters — some brutally cold and snowy, others mild — and while there will be dips and spikes in populations, one warm winter isn’t enough to cause any long-term changes.

“There could be some short term effects … but it’s not a huge concern in the long term,” said Steve Faccio, a conservation biologist with the Norwich-based Vermont Center for EcoStudies.

Still, the strange weather brings with it changes in animal behavior and population growth.

One of the most widely publicized has been the effect on white-tailed deer. Normally, deer need to conserve energy during the winter to avoid starving to death, said Vermont State Wildlife Biologist Cedric Alexander. Deer must work hard to forage in the deep snow, and they’re vulnerable to predators: even pet dogs, who like to chase deer through the woods, can cause them to expend precious energy needed to survive.

This year, though, deer populations are thriving.

“Instead of being subjected to very harsh winter conditions which often cause some level of mortality, they’re really presented with the kind of conditions they might expect to find in a place like Pennsylvania,” Alexander said. “Their mobility is unrestricted so they can move around without expending a lot of energy.”

Moose, on the other hand, may be negatively impacted. Their legs are usually long enough that deep snows don’t hurt survival rates, and their layer of winter fat and heavy coat predisposes them to cold conditions. Even a 50-degree day in January is enough to make a moose overheat; they try to cool down by hiding in the shade of conifer trees, Alexander said.

But the real problem for moose isn’t the warmth: it’s ticks. Winter ticks, to be exact, which are a different species than the familiar summer ticks.

Winter ticks latch onto moose in the early fall and begin months of feeding. A typical moose has 30,000 ticks on its body; sometimes, they can have up to 150,000, Alexander said. Usually, the female ticks will get their fill of blood and drop off the moose’s body. If they land in the snow, they cannot lay their eggs and will eventually die. But without snow on the ground, the ticks are able to reproduce, and Alexander fears that a bumper crop of winter ticks this year could mean trouble for moose calves next year.

“The problem is, the moose didn’t evolve with this tick, so they aren’t really adept at grooming them (off),” Alexander explained. Ticks, carried by deer, were brought north to moose territory as deer expanded their range north with human development. While agile deer can reach just about any body part to nip an irritating tick off, moose are less mobile, and the tens of thousands of ticks that cling to them grow engorged with blood, reaching the size of a grape.

“It actually causes anemia through loss of blood proteins,” Alexander said. “Just as important is the irritation, and the amount of time a moose spends rubbing against trees to alleviate the itching. 
They’re not feeding, they’re not resting, they’re constantly stressed, and instead of conserving energy they lose body weight.”

What’s more, the animals often rub their insulating guard hairs right off, leaving them vulnerable to hypothermia during a cold spring rain. For calves, tick infestations can prove fatal.

Other mammals hurt by a mild winter include snowshoe hares, which are visible to predators when there’s no snow to match their white winter coats, and small rodents like meadow voles, shrews and mice.

With a couple of feet of snow on the ground, such burrowing animals can still reach their food sources — roots, seeds and grasses — but they’re protected from predators like foxes and owls, Alexander said.

Of course, the rodents’ bad luck helps their predators pass the winter months fat and happy. 

 'An ecological cascade'

Other predators that inhabit Upper Valley forests, like fishers and weasel,s could also benefit from the mild winter, though for different reasons, according to Faccio of the Center for EcoStudies. 

Such animals employ an evolutionary tactic called delayed implantation, which allows them to halt the development of a fertilized embryo from fall until mid-winter.

If the weather is harsh and food is low, females can abort an embryo. But in mild winters, more fisher and weasel embryos will develop until birth, perhaps causing a slight surge in populations, Faccio said.

Predators also impact bird populations. Squirrels and chipmunks, which prey on song bird nests, may be thriving with the abundance of available food this year, said bird biologist Pamela Hunt of New Hampshire Audubon.

“I wouldn’t be terribly surprised if there was a high predation (on birds eggs and chicks) this summer because of the mild winter,” Hunt said. “It’s one of those interesting ecological cascades.”

Most birds, though, benefit from mild weather. Though species like black-capped chickadees that normally overwinter in the Upper Valley are well adapted to freezing temperatures, warmer weather only increases their chances for survival. And given the lack of snow, finding food in the woods and fields has been easier for birds, so there have been fewer at feeders, Hunt said.

But for birders who venture further afield, this winter has produced some interesting surprises.

“The famous story right now is there’s a bird called the Cape May warbler that normally spends its winters in the Caribbean that’s been hanging out on the New Hampshire coast,” Hunt said. Further inland, birds like the yellow rumped warbler have been sighted in the White Mountains, orioles have been frequenting feeders in Concord, and the American redstart, another Caribbean winterer, was seen in Brattleboro as late as mid-December.

It’s not that the birds have intentionally stuck around due to the warm weather, Hunt said. Every year, a handful of migrant songbirds have “messed up migration systems” and get stuck in cold climates. Usually, they die. But this year, a lack of nasty weather has enabled many of the birds to stay alive.

Unlike songbirds, water fowl like ducks and geese aren’t programmed to head to a specific overwintering site. Instead, they partake in “short distance hopping,” going only as far south as they need to find open water and food sources.

“They only migrate until they get to a place that’s suitable, then they stop,” Hunt said. With the Connecticut River largely unfrozen this year, ducks have stuck around, and even Canadian geese have been spotted flying north. 

Fish and frogs

The unusually sparse ice cover has implications for fish as well, said Rich Kirn, a Vermont State Fisheries Biologist.

Typically, a type of ice called “anchor ice” builds up in the bottom of stream beds. During spring break-up, hunks of ice scraping through the stream channel can kill the eggs of spring spawning fish like rainbow trout. With trout populations still reeling from Tropical Storm Irene, this year’s lack of anchor ice could help aid in the species’ recovery.

On the other hand, Kirn said, spring flooding is important in opening up spawning sites for rainbow trout. And given the lack of snowpack and precipitation in general, the National Oceanic and Atmospheric Association’s Northeast River Forecast Center predicts below average spring flooding across Vermont and New Hampshire.

Of course, said NOAA meteorologist Hayden Frank, that could all change with a few days of heavy spring rains.

“This is just a general outlook,” he noted. “It doesn’t mean to say there won’t be spring flooding.”
But even with lots of rain in the forecast, it will be difficult to make up the flooding effects of a heavy snowpack, and flooding will likely be less severe then last year, Frank said.

Amphibians like wood frogs, peepers and salamanders also depend on spring rains to create the ephemeral spring ponds, or vernal pools, that provide vital breeding habitat. But such animals are also affected by winter conditions. 

Wood frogs and peepers overwinter by burrowing just beneath the leaf litter and employing a natural anti-freeze that allows their bodies to drop well below freezing while still staying alive. If the frogs come out too early due to warm weather, they might not be able to revive their antifreeze capabilities if a hard frost were to follow, said Faccio of the Center of EcoStudies.

Salamanders, lacking such antifreeze capabilities, generally burrow in the warm earth below the frost line. In typical winters, a layer of snow acts as an insulator, keeping the ground from freezing too deeply. This year, the lack of snow could mean that some salamanders who didn’t bury themselves deep enough might be susceptible to freezing to death.

Bulbs and bugs

Wooster, who owns Sunrise Farms in White River Junction, is keeping his fingers crossed that the lack of snow cover has been tempered by mild temperatures. In addition to insulating salamanders, snow also prevents fall bulbs like garlic from being damaged by frost. Wooster has measured six inches of frost in the ground this year. Last year, he said, there was hardly any.

He hopes the extra mulch he’s put over his garlic beds will protect them until spring, and he doesn’t anticipate any delay in spring planting. What he’s really worried about are insects.

“I subscribe to listservs from southern New England vegetable growers, and they have certain insects down there that we don’t have,” Wooster said, noting that northern New England’s cold winters generally keep such insect populations  in check. “Whenever we have a mild winter like this, I have a general panic over all these (pests) I haven’t had to know about.”

Vermont State Zoologist Mark Ferguson said that Wooster’s fears aren’t unfounded, though it would likely take several mild winters in a row to really facilitate the spread of new insects north. This year’s winter and last fall’s rains could result in an increased number of ticks and mosquitoes, Ferguson said, but there could be other, more pleasant consequences as well.

The giant swallowtail butterfly, for example, usually lives in warmer climates. On rare occassions, it’s been spotted in Vermont, but there are no recorded instances of it breeding here. Last summer, several were spotted in Vermont, and entomologists have found their eggs on plants. Ferguson is hopeful the mild winter might help the eggs survive.

“In some situations, southern species live just on the edge (up here),” he said. “If they can survive on that edge during a winter that’s not too harsh, maybe that gives it an opportunity to move north.”

And then there are the bears. 

Kilham, who’s been studying black bears for 14 years, said winters like this don’t necessarily have positive or negative impacts on bears, but it does make for some curious situations. Female bears with cubs den up no matter what, but thanks to a bumper crop of beech nuts and mountain ash berries last fall, many male bears didn’t go into hibernation at all.

“The male bear’s strategy is to get big enough to mate, because only the largest 10 or 15 percent of males do all the mating,” Kilham said. Eating all winter leads to more weight gain than sleeping in a den, “and the goal of any male is to gain weight.”

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