Field Guide to October 2022

Bats on the Move

By Emily Anderson

An autumn chill is in the air, and all across Vermont’s landscape, wildlife big and small are preparing for winter. Although not noticed as often as flocks of birds or frantic squirrels, bats are on the move too.

When most of us think of ‘flying migrants,’ birds usually come to mind first. But did you know that Vermont is home to three migratory bat species? As days shorten, our Eastern Red, Hoary, and Silver-haired bats take flight for warmer winter roosts. In North America, Eastern Red and Silver-haired bats are considered long-distance migrants that may travel 1,000 km or more between their summer and winter habitats. Meanwhile, Hoary Bats are partial migrants that may over-winter in small colonies in areas where winter temperatures are tolerable.

Eastern Red and Hoary bats have a special trick to stay warm—their own personal sleeping bag! These two bat species have specialized, fur-covered tail membranes (extensions of skin between the hindlegs) that they can tuck around themselves for extra warmth.

However, not all Vermont bats spend winter in the south. Six cave bat species live in the state: Big Brown Bats, Little Brown Bats, Indiana Bats, Tri-colored Bats, Northern Long-eared Bats, and Eastern Small-footed Bats. As colder weather sets in and insect populations decline, these bats head to caves and mines (also known as hibernacula), where they will wait out the cold months in hibernation. Bats are one of Vermont’s few true hibernators. While in their hibernacula, they often remain in torpor for 12–19 days at a time (some Little Brown Bats have gone as long as 83 days!) and only arouse to drink and urinate. During this time, their heart rate slows from 400–1000 bpm to 20 bpm, and their body temperature drops within a few degrees of the cave.

However, hibernating isn’t as easy as it sounds. Bats survive the winter on the fat they store before hibernation begins. Unable to replenish their reserves over the winter, any increase in energy expenditure can be quite costly. For example, waking up requires a tremendous amount of energy. Sometimes, external temperature fluctuations can wake bats, causing them to change locations within their hibernaculum. Any disturbance—such as human intrusion—can also wake bats, so leaving potential and known hibernacula alone in winter is extremely important. Finally, White Nose Syndrome, a fungal pathogen responsible for devastating declines in North American cave bat populations, also increases energy expenditure while hibernating due in part to metabolic changes in infected bats.

Like many of Vermont’s birds and insects, bats will soon disappear from our skies until spring returns. In the meantime, if you encounter a bat roosting outdoors once freezing temperatures arrive, please contact your nearest wildlife rehabilitator for guidance.

Frightening Fungi: Pumpkins, Ghosts, And Zombies (Oh My!)

By Meg Madden

October—and fall mushroom season—is upon us, and plenty of Vermont fungi are adding to the spooky Halloween vibes.

While carved jack o’lanterns are lighting porches and front steps, their mushroom counterparts illuminate the forests with an eerie glow. The bright pumpkin orange Omphalotus illudens, or Eastern Jack O’ Lantern Mushroom, is bioluminescent! Amazingly, the gills of this species emits a faint green light that can be seen on the darkest of nights. The light is produced by an enzyme called luciferase, the same type of chemical responsible for bioluminescence in fireflies. You can find these large, showy mushrooms growing in dense clusters on hardwood stumps and buried, decaying tree roots. Foragers hunting for edibles such as Chicken Of The Woods and Chanterelles should be careful not to confuse them with the poisonous jack o’ lantern mushroom. Though not deadly, consumption can cause severe gastrointestinal symptoms that can last several days.

This month, the ghostly white forms of Shaggy Mane Ink Caps, Coprinus comatus, may be haunting a lawn near you. Particularly abundant after rain, these cylindrical mushrooms can seemingly appear out of nowhere and disappear just as quickly. Ink cap mushrooms undergo a self-digestion process called deliquescence, whereby they turn themselves into inky, black goo. The spores of shaggy manes, otherwise trapped deep inside the bell-shaped caps, are exposed to air currents as the mushrooms melt themselves from the bottom up. This species can go from pristine white to a black puddle on the grass in as little as 24 hours! Ink cap mushroom ink can actually be used for writing and drawing. The illustrations in the book Entangled Life by Merlin Sheldrake were created using the ink from shaggy mane mushrooms.

It’s not difficult to see how Dead Man’s Fingers, Xylaria polymorpha, got its name. The slender, crusty, charcoal gray to black mushrooms of this macabre-looking fungus resemble creepy corpse fingers in a spine-chilling movie. Though often found growing singly or in small groups on decaying logs, sticks, and wood mulch, they occasionally appear in larger numbers—zombie apocalypse-style—as though the hands of the undead are clawing their way out of the forest floor. As frightening as that may sound, Dead Man’s Finger fungus is actually quite beneficial, happily going about its important job as a decomposer. As critical members of nature’s recycling crew, fungi such as Xylaria polymorpha play an essential role in forest ecology. Without them, wood would never decay, we would be buried deep in piles of dead trees, and valuable nutrients would be locked up and unavailable to other organisms. Now THAT’S scary!

That Gnawing Feeling In Your Gut…and the Guest that Just Won’t Leave

By Jason Hill

Some…thing, crawling around in your body. Well, anyone could understand how that would cause unease as a Promethea Silkmoth (Callosamia promethea) prepares to undergo winter hibernation inside the silken walls of its cocoon. You would be able to feel it… moving…. wriggling… burrowing… gnawing… faster during the warmth of day, and more slowly as the temperature descends like a black curtain at night. With nowhere else to go, you would reluctantly settle in for a winter’s nap…with the guest that just won’t leave.

But let’s stop this story here and go back to a more carefree time…in the previous June when Promethea Silkmoths eclose (emerge) from their cocoons in New England. By the afternoon of the same day they emerge, those fresh adult moths are mating, and by nightfall, oviposition (egg laying) is underway. In a few days, the adult silkmoths are already spent and dead. In a few more, the eggs hatch, and that is when our story darkens again.

The attack comes stealthily, under the glow of the moon, which is unusual for wasps. As young, unsuspecting Promethea Silkmoth caterpillars rest side-by-side in June and July, a large female ichneumon wasp (member of the Enicospilus americanus species complex) descends to stab a single egg into the flesh of several caterpillars. The afflicted caterpillars curl tightly, desperately—a futile attempt to arrest the, now, nearly inevitable event that will unfold in autumn. The parasitoid ichneumon eggs hatch quickly but are largely inactive, for the time being, inside their silkmoth homes.

In late summer, with wasp attacks a distant memory, Promethea Moth caterpillars spin a silk cocoon in which they hope to overwinter, suspended from a silk thread on a branch. For the unlucky caterpillars internally carrying an E. americanus larva, this hormonal change signals the wasp larva to rapidly grow—consuming its silkmoth host from the inside…out.

But safety hasn’t come for those silkmoth caterpillars whose story continues, those who escaped the E. americanus attacks back in early summer. Because now, the smell of fresh-spun silk attracts another attacker—ichneumon wasp parasitoids from the genus Gambrus. Female Gambrus spp. wasps pierce the silk cocoon and deposit eggs atop the caterpillar. The wasp eggs hatch quickly, and the larvae consume their silkmoth host from the outside…in.

The E. americanus and Gambrus spp. larvae both pupate and overwinter restfully within the hollowed-out hull of their formerly living host. This is the fate of nearly two-thirds of Promethea Silkmoth caterpillars that survive until October. The remaining non-parasitized third can look forward to a long winter…and a very short spring.

Primary Sources: Peigler 1994, Juice and Heinrich 2017, and https://bugguide.net

Masked Bees (Genus Hylaeus)

By Spencer Hardy

Buried deep within the thorny recesses of a rose plant, a little grub is wrapped in a plastic bag regulated by its long-dead mother. After five months of freezing and thawing, this little grub will split open down the back and emerge as an adult Masked Bee (genus Hylaeus). Among Vermont’s smallest bees, these approximately 5 mm, black and yellow insects are one of several bee genera that nest within hollow plant stems. There, they develop into pupae and overwinter before emerging in the spring. By taking advantage of these pre-existing cavities, Masked Bee nests may stay drier and receive protection from the elements—however, they aren’t entirely safe. An odd creature known as a Carrot Wasp (genus Gasteruption) is a nightmare specially designed for Masked Bees. Armed with an ovipositor longer than their body, female Carrot Wasps can reach deep inside bee nests to lay eggs that will devour the baby bee and all the food collected by the mother Masked Bee.

If you haven’t done your fall yard work yet, think about these tiny dramas that are likely playing out all around you. Check out this resource from the Xerces Society to learn more about bee nesting requirements and habitat management, even on a small property.

A Poolside Feast for Natural Predators

By Kevin Tolan

Vernal pools act as nurseries for certain amphibians, a haven for their eggs to hatch. Because they generally dry up each summer, fish, which predate amphibians and their eggs, can’t persist. Not all threats come from below, however. With such a large bounty of easy prey, many species hunt in and around vernal pools.

Perhaps the most vocal vernal pool hunters are Barred Owls, widely recognized by their “who-cooks-for-you?” hooting. As Wood Frogs and Spotted Salamanders rise from their winter hibernacula and move across the landscape to their natal pools to breed, they run the risk of being swept away by a Barred Owl with hungry nestlings to care for. Come nightfall, these silent fliers perch on sticks and snags around vernal pools and wait to spring on unsuspecting prey.

Although the spring amphibian breeding season is long over, that doesn’t mean there isn’t still danger afoot. After larval amphibians metamorphose into terrestrial adults and begin to make their way upland to hibernate, they’re exposed to predators ranging from snakes to raccoons to Barred Owls. This can be especially problematic if the amphibians must cross roads, where there is rarely any cover to hide.

With this multitude of predators fiending after our tiny amphibious neighbors, there are simple steps you can take to not contribute to the danger. For instance, on rainy early spring and mid-fall nights, drive slowly to avoid amphibians crossing the road, or better yet, try to stay off the roads altogether. You can also volunteer as an “amphibian crossing guard” to help ferry them across the road; check out North Branch Nature Center to learn more about participating in road crossings.

Ghosts and Witches in Vermont Forests

By Ryan Rebozo

Ghosts and witches’ brooms are staples in Halloween décor and festivities, but you can also find them in Vermont if you know where to look. But beware—how these ghosts and witches’ brooms in our forests interact with their host plants is even scarier than what you may find at a holiday store.

Ghost Pipes (Monotropa uniflora) can be found poking out of the leaf litter in coniferous, deciduous, and mixed forests throughout the state. Their name comes from their pale white color and waxy appearance. White is an uncommon color for plants, who typically depend on green chlorophyll to help convert sunlight into essential sugars. However, Ghost Pipes can forgo chlorophyll because they actually parasitize other plants. It gets more complicated from there because they depend on fungi at the roots of trees to be their hosts, and those fungi are the ones that actually receive the nutrients from the trees. While their method for generating food is uncommon, they still rely on bumblebees to pollinate their single flowers, like many other plant species.

Witches’ Broom is the colloquial name given to a dense cluster of branches and twigs that grow to form a round mass in trees. This odd growth of dried and discolored twigs is the result of the tree responding to stress. The main culprits include fungal, bacterial, and viral infections; parasitic plants; nematodes; mites; and even aphids. The Witches’ Broom itself isn’t harmful to the tree, and many trees can persist with them indefinitely. However, they ultimately indicate an underlying source of stress.

Witches’ Broom can be found year-round, while Ghost Pipe is most readily seen in the summer and early fall. Keep an eye out for these next time you are in the woods and consider the many interactions the trees around you have with their environment. And, as always, make sure to share your sightings with the Vermont Atlas of Life on iNaturalist.