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Hibernation

Wood Frogs & Spring Peepers On The Move

3-29-16 road frogs 015Although the temperature hovered around 32°F.  last night in central Vermont, wood frogs and spring peepers were on the move.  Usually it is above 40° or 45° before you see the earliest of our breeding amphibians, but a few hardy souls ventured forth to their breeding pools and ponds under cover of darkness and  rain yesterday.  Those that breed in vernal pools are in a hurry to take advantage of every day, as the eggs they lay must complete metamorphosis by the time their pool dries up, often in mid- to late summer.

Both of these species of frogs are freeze tolerant.  Wood frogs are coming out of a state in which they haven’t taken a breath and their heart hasn’t beaten for several months.  Prior to hibernation they convert glycogen in their bodies into glucose, a form of antifreeze that helps prevent the water within their cells from freezing, which would kill them.  However, the water outside their cells does freeze.  Amazingly, wood frogs can survive having up to 65% of this water frozen, yet when warm weather arrives, they thaw and move about in a matter of hours.

If you rescue these woodland amphibians that are crossing roads (where so many of them get run over at night) during their migration to their breeding pools, take note of the temperature of their body.  Often they are still quite cold to the touch — colder than the air, even – which fortunately makes it difficult for them to move fast enough to escape your helping hands. (Photo: Amorous wood frogs getting a head start as they cross a road to get to breeding pool.)

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Painted Turtles Basking

3-23-16 painted turtles 033Being an aquatic species, most painted turtles hibernate in the mud at the bottom of ponds. They dig down as far as ten feet where they spend the winter hovering around 43°.  In the spring, when the temperature of the water approaches 60°, painted turtles begin actively foraging, but the first priority upon awakening is to warm up their bodies.  Turtles are ectothermic, or cold-blooded, thus the temperature of their bodies is determined by the  environment that surrounds them.  To be active, painted turtles must maintain an internal temperature of 63°- 73°.  They reach and maintain this temperature by basking in the sun, particularly in the cold, first weeks of spring.  Once warmed up, the turtles will forage, and when they begin to cool off, basking resumes.

Competition for basking sites such as floating logs and rocks can be fierce.  It is not unusual to see many painted turtles lined up on a floating log, or turtles piled one upon the other on a rock in an effort to maximize the effect of the sun’s rays.  The heat they’re obtaining increases their metabolism, aids in digestion and allows males to start producing sperm.  The sun also strengthens their shells and reduces the amount of algae on them, thereby reducing the chances of bacterial or fungal infection.

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Woolly Bears Wandering

3-15-16 woolly bear 119 Woolly bears (larvae of the Isabella tiger moth) are on the march again- several weeks before I have seen them in past years, no doubt due to the warm weather we’ve experienced lately. They are one of the few moths or butterflies that overwinter as caterpillars. In the fall, often around the time of the first frost in the Northeast, woolly bears are often seen crossing roads as they wander frenetically prior to hibernation. At this time their body produces a chemical called a cryoprotectant that acts like an anti-freeze which protects living tissue against damage from freezing and thawing. They remain curled up in a protected spot, such as in leaf litter or under loose bark, nearly frozen solid all winter. When spring arrives and the temperature reaches the high 40’s and 50’s they become active again, feed for a few days, and then pupate inside a cocoon made with their own bristles. Adult Isabella tiger moths emerge in about a month, anywhere between April and June, mate, and lay eggs. Within two weeks the eggs hatch. In New England a second generation of woolly bears will be produced and these are the larvae that overwinter. (In even colder regions, such as the Arctic, there isn’t enough time for woolly bear caterpillars to consume enough food to achieve adulthood within a year, so they spend several summers feeding, hibernating each winter, for up to 14 years.)

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Green Frogs About To Take The Plunge

11-9-15 A. bullfrog 005Most Green Frogs have disappeared over the last few weeks, but this male (eardrum, or tympanum, is larger than his eye) was basking in the last bit of sunshine he will see or feel for the next five or six months. Soon he will take the plunge and bury himself in leaf litter at the bottom of the pond or lay, partially exposed, on the mud beneath the leaves. (Green frogs typically hibernate in water, but occasionally overwinter on unfrozen stream beds or seeps, as well as underground.) Aquatic turtles can shut down their metabolism to a greater extent than frogs, so they are able to survive hibernation buried in mud, where there is little oxygen, but frogs overwintering in a pond must have their skin at least partially in contact with oxygen-rich water. Green frog tadpoles will typically, but not always, overwinter prior to metamorphosing the following spring.

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Bumblebees Raising Queens & Males

9-11-15  bumblebee emerging IMG_5476Unlike a hive of honeybees, where the queen and workers overwinter, the only bees in a bumblebee colony that live through the winter are young, fertilized queens. In early fall, bumblebees begin producing new queens as well as males in order to allow the colony to reproduce. Once the adult virgin queens and males have emerged from the silk cocoons within their pupal cells, they leave the hive. The male bees spend their time feeding on nectar and trying to mate with the new queens and the young queens mate with several males. Once fertilized, the queens continue to feed, building up fat bodies for the approaching winter. Once enough fat bodies are stored, queens begin searching for suitable overwintering locations. Overwintering sites are often in an abandoned chipmunk or mouse burrow, or in soft soil or compost, where they can survive temperatures down to – 5° F. due to a kind of “antifreeze” they produce. The rest of the hive (old queen, workers and any remaining males) dies once cold weather arrives. In the spring the queens emerge and start new colonies. (Thanks to Natalie Kerr & Sadie Brown for making this post possible and accurate.)

Photo by Sadie Brown: A recently-excavated underground colony of bumblebees (by a chemical-free “pest” controller) contained several wax pupal cells, as well as wet, silver-haired bumblebees (their color appears as they age) emerging from some of the cells. At this time of year, they are most likely to be queens or drones.

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Black Bears Seeking Protein

9-2 hornet nest torn by bear 083Although insects and animal matter make up less than 10% of the annual black bear diet, they are a crucial part of it. Black bears get most of their animal protein from ant brood, hornet larvae, tent caterpillars, march fly larvae, grubs (especially June beetle grubs), and snow fleas. Among the most preferred sources are bee and hornet larvae. Berries and other fruit don’t have a great amount of protein, but they do have some (blackberries = 2 grams of protein per cup). If the summer berry crops fail, insect brood is especially important, especially at this time of year, when bears are seeking protein, fats and carbohydrates, putting on as much as 30 pounds per week to sustain themselves through the coming months of hibernation.

When tearing apart a beehive, yellow jacket nest or bald-faced hornet nest (see photo), bears do get stung, particularly on their ears and faces (their fur is fairly impenetrable). Apparently the reward is worth the aggravation. After filling themselves with brood (and in some cases, honey) black bears shake vigorously in order to rid themselves of any insects that are caught in their fur.(Thanks to Alfred Balch for photo op.)

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Queen Bumblebees Foraging

queen bumblebee 098Most bumblebees, unlike honeybees, die in the fall. Only the young, fertilized bumblebee queens overwinter. When they emerge early in the spring, each must start a new colony, with no help from worker bees. The queen builds a ball of moss, hair or grass, often in an abandoned rodent nest or small cavity. Within this ball the queen builds a wax honey pot, and provisions it with nectar from early-blooming flowers. Next, she collects pollen and forms it into a mound on the floor of her nest. She then lays eggs in the pile of pollen, and coats it with wax secreted from her body.

The queen bumblebee keeps her eggs warm by sitting on the pollen mound, and by shivering her muscles, raising her body temperature to between 98° F. and 102° F. For nourishment, she consumes honey from her wax pot, which is positioned within her reach. In four days, the eggs, all of which will become female workers, hatch. The bumblebee queen continues her maternal care, foraging for pollen and nectar to feed to her larvae until they pupate. After this first brood emerges as adult bumblebees the queen concentrates her efforts on laying eggs. Unfertilized female worker bees raise the larvae and the colony swells in number. At the end of summer, new queens (females) and males are produced in order to allow the colony to reproduce. After the new queens mate and become fertilized, the males all die, along with the female worker bees. The queen then seeks shelter for the winter. (Photo: Tri-colored Bumblebee queen collecting Trailing Arbutus nectar or pollen)

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