Even during these short days and long nights of December, there’s still plenty of life in the fading light. Once we pass the winter solstice, which strikes at precisely 11:19 PM on December 21st, more light will begin to creep back. Until then, here’s some wintry natural history to keep you going.
By Kent McFarland
Economically and ecologically important, Balsam Fir is a keystone species of the eastern North American boreal zone. The provincial tree of New Brunswick, Canada, it can form dense single species stands in some areas of northeastern North America, especially in the high mountains.
Trees at the leeward edge of the canopy opening in the wave are exposed to winds and die from loss of needles and branches due to heavy ice accumulation. Being rocked by the wind while supporting ice loads also causes their fine rootlets – which are important for delivering nutrients to the tree – to break underground. As these trees die, adjacent trees experience the same conditions and begin to die. The overall direction of the wave motion is therefore directly related to wind direction. High-elevation forests are often marked by “fir waves.” These are crescent-shaped bands of dead trees that you can see in systematic patterns across the sides of the mountains. The waves are areas of standing dead fir trees with healthy trees surrounding them. Fir waves move very slowly, over decades, in the direction of the prevailing wind. Wind velocity at the edge of the tree canopy is over 50% higher than within the forest. Rime ice forms on the trees when water droplets in the air hit solid surfaces and immediately freeze. Rime accumulates more on trees exposed to wind.
Regeneration of waves occurs at about 60 year intervals. As you move back from the dying front of trees the trees are older and older until you reach the following wave of dead trees. If you were to take time lapsed photography of a mountain side, the waves of dead trees would appear to be moving across the mountainside like a wave in the ocean.
By Spencer Hardy
Bees need flowers. But flowers are missing from the Vermont landscape for nearly five months out of the year. As far as we know, bees don’t migrate (but some flower flies do!) so they must be here somewhere, but where? As with a lot of natural history, the answer depends on the species.
Honeybees (Apis mellifera) are the only species active in the depth of winter, with thousands of workers piled up around a single queen inside of the hive, which in Vermont is almost always inside a box. The other ~350 native species don’t get any help from humans and spend the winter in some form of torpor.
With Bumblebees (Bombus), only the queen survives the winter, having mated in late summer or fall. There is a cool new project working to figure out more about the overwintering habits and needs of these queens. A fun fact for your next cocktail party is that there are no male bumblebees anywhere in Vermont from roughly December to June. The only bumblebees alive are lonely queens.
We know much less about the overwintering strategies of most of the solitary bees, yet there is at least one group that can be found relatively easily during the winter months. If you have raspberries or blackberries in your yard, check any medium to large canes that have been broken off or previously cut. You will likely notice that in the center of many such canes there is a hole in the top where the pith has been removed. This is likely the work of a small carpenter bee (Ceratina sp.) which may be the most abundant bee genus in the state. Where the pith once was there could be several adult Ceratina patiently awaiting the arrival of warmer temperatures. Researchers at University of New Hampshire and Iowa State University found that these bees change their gene expression in preparation for a long, cold winter by producing proteins related to fat storage while reducing transcriptional activity related to cellular and muscular structure processes. Having enough fat stored to slowly burn over the winter as they sit tight is the key for their survival.
While other bee species overwinter in hollow stems and twigs, most do so as larvae or pupae. Some winter in rotten logs or tunnels created by beetle larvae, though the majority of species overwinter underground. And if you thought six months of winter was enough, some of our native species are active for less than a month, yet spend 11 months of their life underground! Even in the depths of winter, there’s a wild bee nearby waiting for spring.
By Emily Anderson
Bats are not everyone’s favorite critter. However, they humbly remove up to 1,200 insects per hour in the summer months. Without bats, sitting in your backyard on a sweltering July evening would become unbearable. When the weather turns cold, six out of Vermont’s nine bat species head indoors, settling deep in caves referred to as “hibernacula.” During the winter months, these bats slow their heart rate and metabolism, and remain in a state of torpor to minimize energy loss, rarely waking except when disturbed or in response to warmer temperatures.
This type of hibernation is not unique to bats – other small mammals that remain in Vermont all winter long fall into a similar state. However, for Vermont’s hibernating bat species, it carries an extra risk. Over the past decade, white-nose syndrome (WNS) has plagued bat populations. Pseudogymnoascus destructans, the fungus responsible for WNS, loves cold, damp places, making hibernacula the ideal locations for it to grow and spread. And hibernating bats, whose immune systems get suppressed during torpor, make it easy for the fungus to proliferate. Once introduced to its host, P. destructans invades skin tissue, causing the characteristic white fuzz on both snout and wings. Infected bats also experience increased water loss, frequent arousal from hibernation, and greater depletion of fat reserves. Ultimately, these conditions weaken infected bats, making many cases fatal.
As a result, several bat species have declined in Vermont. Little Brown and Northern Long-eared Bat species are particularly affected, having experienced a 75-90% population loss between 2008 and 2011. Currently, both species are listed on Vermont’s Endangered Species List, along with the Indiana Bat, Tri-colored Bat, and Eastern Small-footed Bat. Despite these grave statistics, some individuals do survive. In some cases, epizootics like this give evolution a strong push in a different direction, encouraging the proliferation of traits promoting greater resistance or tolerance to infection.
Currently, there is evidence that Little Brown Bat populations might be stabilizing, however none of the affected species are out of the woods yet. Scientists still have many unanswered questions. If you’re wondering what you can do to help support Vermont’s bats, the VT Fish & Wildlife Department provides guidelines and answers. To learn more about Little Brown Bats, check out this episode of Outdoor Radio.
By Emily Anderson
The Moose – northern New England’s unofficial mascot – haunts the imagination of hunters, photographers, and wildlife enthusiasts alike. In the warmer months, these graceful woodland giants forage in areas where nutrient-rich aquatic plants are abundant, at times diving 18ft deep to reach their food. In the frigid months when aquatic vegetation vanishes, moose too must disappear from their watery feeding grounds to pursue woody plant material, such as twigs and bark. These food sources offer distinctly fewer calories than their summer feed, making energy precious and its conservation vitally important.
However, moose are designed for harsh winters. Although often seen as similar to deer, moose cope more easily with deep snow thanks to specially formed joints which allow them to lift their legs straight up nearly to shoulder height. Even in feet of snow, moose can move with relative ease and expend less energy when traveling or escaping predators. However, unlike deer, moose are at significant risk of overheating in the summer, due to their large size and thick fur which help them weather bitterly cold northern winters. As the climate warms, these traits which make them perfectly suited to the icy north will become a greater disadvantage, possibly affecting their survival.
Moose are also facing another significant threat to survival: winter ticks. New England winters are becoming warmer and shorter due to climate change. In the past, freezing temperatures and heavy snows have caused tick populations to sharply decline right when they are searching for a host. In contrast, milder winters fail to dent their populations, meaning that moose can accumulate higher numbers of tick nymphs. Unlike deer, moose do not regularly engage in habitual grooming. Ticks often go through several life stages on a moose and reach their final, most voracious state before the moose notices its passengers and tries scratching them off. By that time, it is usually too late. Studies show that these tick counts can range from ten to one hundred thousand individuals per moose, effectively bleeding them dry. These large infestations lead to increased calf mortality and a decrease in female breeding success.
Tick counts on moose in Vermont are lower than those found in New Hampshire and Maine, likely due to Vermont’s efforts to reduce moose population numbers. However, the likelihood of more mild winters coupled with the reduction in reproduction and calf survival means that New England moose could be facing an uncertain future. For now, biologists are monitoring their populations and working with other state officials to develop the best management path forward.
If you want to learn more about moose and ticks, visit the VT Fish & Wildlife Department or check out this episode of Outdoor Radio. If you see moose sign when out exploring backcountry trails this winter, make sure to share your observations with the Vermont Atlas of Life project on iNaturalist.
By Kent McFarland
Mistletoe has been a symbolic plant for thousands of years. In Europe, it became associated with Christmas as a decoration under which lovers were expected to kiss, a tradition that continues in many places today. Of course, this was the European Mistletoe (Viscum album), the only native mistletoe species that ranges across most of Europe. The tradition was carried to the New World where American Mistletoe (Phoradendron leucarpum), similar but with shorter, broader leaves and longer clusters of berries, was adopted. But if you live here in the Northeast, you’re not going to be able to harvest your own mistletoe to hang for the holidays. American Mistletoe only grows in the southern portion of the continent. But we do have a unique mistletoe lurking in our forests, but it looks nothing like the others.
Like other mistletoes, Dwarf Mistletoe (Arceuthobium pusillum) is a bit of a thief, actually a hemiparasite, which means it steals minerals and fluids from its host plant, and also generates some of its own energy through photosynthesis. It grows within the branches of pine, spruce, fir, or tamarack, sometimes causing unusual growths of twigs on the host, called witches brooms.
After a couple to perhaps a dozen years of growth inside the host plant, Dwarf Mistletoe sends reddish-colored aerial stems out of the host branch that bear flowers and fruit. The fruit ripens and fills with fluid, building up pressure until they explode. The sticky seeds can be launched up to twenty feet. And, if they stick to a suitable host branch, they germinate. Of course, the seeds may spread much longer distances by animals too. The new plant penetrates past the cambium layer and into the host’s xylem and phloem tissues, where it steals the nutrients needed for its own growth and reproduction.
Dwarf Mistletoe isn’t an easy plant to find. It’s rare in the Northeast and listed as Endangered in Connecticut, New Jersey, and Rhode Island as well as Threatened in Pennsylvania. We’ve found it on evergreen trees in a few bogs here in Vermont. So keep your eyes open for the aerial stems on host plants, and if you find one, please do kiss and tell! Snap a photo (of the plant!) and report your sighting to the Vermont Atlas of Life on iNaturalist!
By Kent McFarland
Northern Short-tailed Shrews (Blarina brevicauda) are a common small mammal in northern deciduous forests. Weighing a mere ounce and just four inches long, they pack an interesting bite. They’re venomous. These voracious insectivores have chemistry on their side.
Their saliva contains venom that paralyzes prey. It’s strong enough to kill another small mammal and cause a fairly painful, though far from lethal, bite to a human. The venomous saliva is secreted from glands through a duct which opens at the base of the lower incisors, where the saliva flows along the groove formed by the two incisors. As they bite and chew, the venom seeps into the prey.
They have many behavioral and physical adaptations to survive the winter. They build elaborate lined nests, hoard energy-rich food, and forage under the leaf litter and snow when the temperatures allow and stay in the nest when the thermometer dips. They eat >40% more food in winter than in summer, as they increase their metabolism to ward off the cold. Body heat is generated from brown fat, which has a unique protein that allows energy to dissipate as heat.
By Kent McFarland
Most are now frozen, a frog-sicle. But in a few months, they’ll croak up a storm in the pond, back from the frozen, the nearly dead. How do they do it?
In late autumn ice began to form inside the bodies of Wood Frogs. Glucose levels increase in their blood by as much as 200-fold in just eight hours, creating an antifreeze that preserved their tissues and organs through the long winter. The ice penetrated throughout their abdominal cavity encasing all the internal organs. Large flat ice crystals formed between the layers of skin and muscle, and frozen lenses made their eyes white like zombies. Their blood stopped flowing. As much as 65% of the frog’s total body water was locked in ice. Breathing, heartbeat, and muscle movements all stopped. The frozen frogs are in a virtual state of suspended animation. They’re nearly-dead.
By Kent McFarland
Paper birches are beautiful in winter, but many people don’t realize that two species of paper birch trees grow in northeastern North America – Paper or White Birch (Betula papyrifera) and Heart-leaved Paper Birch (B. cordifolia), once considered a variety of White Birch. As its name suggests, the latter species has distinctive heart-shaped, many-veined leaves, and it is restricted to mid- to high-elevation Appalachian and northern forests.
The primary means of distinguishing Heart-leaved Paper Birch from White Birch include:
We know surprisingly little about the exact range of these two species. How low in elevation does Heart-leaved Paper Birch grow? How high does White Birch climb into the mountains? Do their ranges overlap in some areas? And how will these species respond to climate change, or have they already? Observers adding records to Vermont Atlas of Life on iNaturalist, are helping to map these (Heart-leaved Paper Birch map versus White Birch map) and many other species. We hope you will add your observations too.