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Hibernation

Woodchuck Hibernation

2-2-17-woodchuck-280As fun as it would be to see a Woodchuck on Groundhog Day, it’s not likely to occur in New England, even taking into account climate change, at least not yet. Rather than migrate or remain active and adapt to winter conditions, Woodchucks lower their metabolism and hibernate through the winter.   Their heart rate, body temperature and breathing rate are decreased significantly in order to conserve energy.

One assumes that once a hibernating animal’s metabolism is lowered, it remains lowered for the duration of hibernation. However, it turns out that this is not the case. All of the species of hibernators that have been studied have woken up periodically throughout the winter and warmed themselves up. During these two-three day (on average) arousals, the Woodchuck’s body temperature (roughly 38°F. during hibernation) rises to 98.6°F., its normal temperature during the summer. During these arousal times Woodchucks do not eat. Rather, they rely on deposits of stored body fat, which results in their losing about 40 percent of their body mass by the time green plants are available in the spring. Woodchucks’ bouts of hibernation are initially short, then they lengthen to an average of eight days, and then shorten again as the season progresses.

Arousal consumes a lot of energy (a single arousal may consume as much energy as ten days of hibernation) so it must have a crucial function. Theories regarding this function include restoration of depleted nutrients in the blood, invigoration of immune system, elimination of toxic substances, dealing with potassium loss and facilitation of sperm production in males. As of today, however, the reason for this arousal phenomenon has not been determined.

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Leopard Frogs – Too Little, Too Late

leopard-frogs-in-puddle-by-kelly-maginnis-northampton-ma-12-10-16At this time of year one would expect to find Leopard Frogs lying on the bottom of a pond, partially but not completely covered with leaves or mud as they hibernate their way through winter. Because of the depth of a pond, and the fact that in winter the water temperature is around 39°F., ice isn’t an issue at the bottom of a pond, and the frogs and turtles that overwinter there don’t usually freeze.

However, sometimes ponds freeze over before amphibians or reptiles that overwinter in them arrive at their hibernacula. Apparently this is what happened to these Leopard Frogs, and they took refuge in the only open body of water they could find – a large but shallow puddle about 10’ wide by 20’ long in a dirt road. Shortly after they arrived temperatures dropped and the frogs were trapped under (and eventually will be encased in) the ice. Unlike Wood Frogs, Spring Peepers and Gray Treefrogs, Leopard Frogs are not freeze tolerant, so their demise is inevitable. (Thanks to Kelly Maginnis for photo, and Jim Andrews for his herpetological expertise.)

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Black Bears Gorging

10-28-16-corn-203Black bears are omnivores as well as opportunists.  They will eat almost anything that they can find, but the majority of their diet consists of grasses, roots, berries, nuts and insects (particularly the larvae).  As the days cool, and the time for hibernation nears, black bears enter a stage called “hyperphagia,” which literally means “excessive eating.”  They forage practically non-stop — up to 20 hours a day, building up fat reserves for hibernation, increasing their body weight up to 100% in some extreme cases.  Their daily food intake goes from 8,000 to 15-20,000 calories. Occasionally their eyes are bigger than their stomachs, and all that they’ve eaten comes back up.  Pictured is the aftermath of a Black Bear’s orgy in a cornfield.

If you  share a bear’s territory, be forewarned that they have excellent memories, especially for food sources.  Be sure not to leave food scraps or pet food outside and either delay feeding birds until bears are hibernating (late December would be safe most years) or take your feeders in at night.

NOTE:  Orders for 2017 Naturally Curious calendars must be received by October 31.

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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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