An online resource based on the award-winning nature guide

Rodents

Beavers Mating

2-17-17-beaver-img_3766Under ice-covered ponds and lakes in dark, cold water, sometime between December and March, beavers mate. Latitude and climate affects the length of the breeding season, which is shorter and later in colder, more northern locations and longer and earlier in warmer, more southerly regions. February is the peak mating season for New England beavers.

Beavers are classified as monogamous, as once a bond has formed, they remain as a pair throughout their life until one of the pair dies, at which point a new mate is found. However, this does not mean they don’t stray. In a study of beaver colony genetics, researchers discovered that more than half of the litters had been sired by two or more males. So much for monogamy.

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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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Check Your Bird Feeder Before Heading To Bed

1-30-17-flying-squirrel-img_0397If you feed birds, you might want to glance at your feeders on your way to bed at night. With luck, you may encounter a Northern or Southern Flying Squirrel, or a swinging feeder indicating the recent departure of one. These nocturnal rodents remain active all year and often take advantage of the ample supply of food that bird feeders provide. Flying squirrels often refurbish abandoned tree cavity nests of birds and squirrels for winter use. During very cold weather they stay in these nests for prolonged periods, often huddling with several other flying squirrels. The relative warmth of this winter means the chances of seeing a “flying” night visitor at your feeder are greatly increased.

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Beavers Especially Vulnerable

9-28-16-coyote-and-beaver-20160927_3275Little did I know when I wrote yesterday’s post about the silver lining of our low water levels that I would so quickly encounter another predator benefiting from the current drought. I have spent a considerable amount of time this summer watching three generations of beavers do their best to survive as their pond proceeded to diminish to the point of exposing one of their lodge entrances and confining them to an increasingly small body of water. The underwater entrances to a beaver lodge are vital to their protection, and predators are well aware of this.

Yesterday the importance of water as a protective barrier was made very clear to me when a coyote appeared on the opposite shore of the beaver pond from where I sat. It stood for several seconds exactly where the beavers leave the pond on their way to nearby woods to cut poplars and birches which they haul back to their pond to eat. A well-worn trail marks the spot. You could imagine the coyote, upon surveying the shallowness of the pond, telling itself to be patient, as better days were just around the corner.

Moments after the coyote left, the mother beaver got out of the pond precisely where the coyote had been standing and took a few steps before sniffing the ground and then the air (see insert). Being nocturnal, beavers have an acute sense of smell which they use for detecting danger, food and for communication with each other. It took mere seconds for the beaver to detect the scent of the coyote, at which point she turned and sought refuge in the dwindling amount of water remaining around her lodge.  May the heavens open up soon.

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Beavers Consuming Herbaceous Plants

8-31-16 beaver cutting fern 052

One associates Beavers with a fairly strict diet of bark and twigs. While their winter diet consists primarily of woody plants, they consume a variety of herbaceous and aquatic plants (as well as woody) during the spring, summer and fall months. Shrubs and trees make up roughly half the spring and autumn requirements, but as little as 10% of the summer diet when herbaceous plants such as sedges and aquatic plants become available.

Recent observation of a local active Beaver pond revealed that Interrupted Fern (Osmunda claytoniana), Jewelweed/Touch-Me-Not (Impatiens capensis) and grasses are high on the list of preferred foods of one Beaver family during the summer, although woody plants such as poplars (Populus spp.) and Paper Birch (Betula papyrifera) have also been consumed in fairly large quantities.   All too soon Beavers in the Northeast will be limited to the bark of branches they’ve stored under the ice. Until this time, they take advantage of the accessibility of more easily digested herbaceous plants. (Thanks to the Shepards and Demonts for photo op.)

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Meadow Voles Soon To Begin Breeding

2-23-16  meadow vole 036

Under perfect conditions, with no predators, no deaths and abundant food, a pair of meadow voles (Microtus pennsylvanicus) could produce a million descendants in a single year. Because they are prey for nearly every meat-eating animal that exists, however, their population, while large, is nowhere near this.

Even though the number of meadow voles is relatively high and they are active day and night, year round, it is unusual to actually set eyes on one. What we do find, especially this time of year, are meadow vole signs in the snow: mazes of runways on the surface of the ground that are exposed as snow starts to melt, air-exchange holes originating in their tunnels and extending to the surface of the snow, tracks and entrance/exit holes to their tunnels.

The social behavior of meadow voles is about to undergo a seasonal change. During the winter, when they are not breeding, meadow voles are more social and commonly share their nests, probably to conserve heat. In another month, however, as breeding begins, females become fiercely territorial towards other females, and males are aggressively establishing dominance over each other. The peaceable subnivean meadow vole kingdom is about to come to an end. (Thanks to Susan and Dean Greenberg for photo op.)

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Porcupine Tracks

2-5-16 w's porcupine IMG_3938Alas, yesterday’s Mystery Photo ‘twas not made by a squirrel loaded down with a bag of nuts, a guess hazarded by one reader, but, as most of you knew, it was created by a Porcupine, or Quill Pig (Erethizon dorsatum). A bit pigeon-toed, Porcupines walk with their feet pointed slightly inward, with their feet flat on the ground. Their pebbly soles rarely leave a distinctive pattern, and their toe pads are not usually evident, but under the right conditions, their nails do make an impression. Usually a Porcupine’s quill-laden tail is raised slightly as it moves, but occasionally it drags along the surface of the snow as the Porcupine walks, producing a broad band composed of very fine lines that weaves between the Porcupine’s tracks, as in yesterday’s photo.

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