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Rodents

Eastern Chipmunks Soon To Retire Underground

Unless global warming extends the normal activity of Eastern Chipmunks, most have or will shortly disappear into their tunnels where they have gathered and stored their winter food supply underground in a special chamber, or larder.  Up to half a bushel of nuts and seeds can be stored here.  They will visit this chamber every two or three weeks throughout the winter, grabbing a bite to eat between their long naps. 

In order to minimize the number of trips taken to fill their storage chamber, chipmunks cram their cheek pouches as full as possible.  The contents that researchers have found in one chipmunk’s two pouches include the following (each entry represents the contents of one chipmunk’s pouches):   31 kernels of corn, 13 prune pits, 70 sunflower seeds, 32 beechnuts, 6 acorns.

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Beavers Grooming

Beavers spend an inordinate amount of time grooming themselves (and each other). Both inside their lodge and on land a beaver tucks its tail between its legs, sits up on its hind legs and spends up to an hour at a time fastidiously combing through its fur often multiple times a day. 

Both front and hind feet are pressed into service.  The two inner toes on each hind foot are modified for grooming – the second toe has a “split nail” with a nail and a horny growth between the nail and the toe which has a finely serrated upper edge that serves as a fine-toothed comb.

Grooming serves two purposes.  One is to remove debris from the coat, from algae to burrs and parasites.  The other is to waterproof the beaver’s coat. A beaver applies an oily substance from its anal glands to the outer layer of hair with the help of its toes, thereby preventing its inner, denser, underfur from getting wet.

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Beaver Scat Anomaly

Finding an animal’s scat is usually pretty straight forward. The shape, size and contents (in this case egg-shaped, one-inch pellets of wood fibers resembling sawdust) of scat tells you who likely deposited it. But the location and amount of this beaver’s scat is highly unusual.

This pile was discovered on a road that passes between two large bodies of water. While beavers are commonplace here, finding their scat on dry land is an anomaly. Beavers are known to defecate only in water.

Often you will find beaver scat where they have been working, such as in the water right below a dam, but usually there are only a handful of pellets, if that —nowhere near the amount in this photograph. One can only wonder what might have caused this unusual deposit. (Photo by Jody Crosby)

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Beavers & Pounding Headaches

Beavers will do their very best to secure fresh cambium as long as they have access to land.  Even when thin ice starts to form, they are undeterred.  You can hear them as they use the top of their heads to bump up against the ice in order to break through and create a pathway to shore.  Thanks to Kay Shumway, a beloved friend, I had ten good years of observing this behavior every late fall/early winter.  Eventually the thickness of the ice confined the beavers to their lodge and the surrounding water beneath the ice, but until that happened you could count on seeing the sun glinting off the ice shards that inevitably ended up on top of the beavers’ heads.


Porcupines Mating

It’s doubtful that there is a female human that would want to change places with a female porcupine.  She (female porcupine) may only copulate once a year.  When that momentous occasion occurs, she is sprayed by her mate with urine from head to toe as part of the mating process.  And finally, she spends 11 months a year, every year, either pregnant or lactating. 

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Beavers Actively Winterizing Lodges

There are two noticeable differences in the appearance of an active beaver lodge in the fall as opposed to the summer.  One is the presence of a growing pile of freshly-cut branches adjacent to the lodge.  These branches provide resident beavers with the nutrition they will need during the winter months when herbaceous plants are neither available nor accessible.

The second change noticeable in a fall lodge is the presence of massive amounts of mud.  Branches are often placed on top of this layer of mud, so you have to observe the lodge before that happens in order to see the extent of the mud layer.  It provides protection from harsh winter winds which would significantly lower the temperature inside the lodge.  Together, a blanket of snow and a layer of mud serve as excellent insulation for beavers living in the lodge.

In the Northeast, where the temperature often dips into the single digits or lower in the winter, the interior of an active beaver lodge maintains a relatively stable 33° F. – 35° F., roughly the temperature of the water, thanks to the ingenuity of these rodent architects.

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Muskrats Foraging

Usually at this time of year, Muskrats are restricted to foraging beneath the ice and eating their mostly herbivorous diet inside “push-ups” — huts made out of excavated vegetation that have been hollowed out and serve as protective outposts where they can eat and rest. Because of warmer weather this winter, many ponds have retained open areas where Muskrats (and Beavers) can climb out of the water and enjoy sunshine (if they’re lucky) and fresh air while they eat.

Unlike Beavers, which store their winter food in a pile adjacent to their lodges in the fall, Muskrats forage for food on a daily basis throughout the winter. While occasionally they eat small fish, clams, snails and turtles, Muskrats’ preferred diet is the roots, stems, leaves, and fruits of many water plants, such as cattail, water lilies, and rushes. Equipped with a thick, waterproof coat of hair, they are capable of remaining submerged up to 15 minutes collecting food due to a decreased heart rate and oxygen stored in their muscles.

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What Determines The Internal Air Temperature Of An Active Beaver Lodge In Winter?

Regardless of the outside temperature, the interior of occupied beaver lodges has a fairly stable temperature of about 32°F.  This is due to several factors, one of which is insulation. Beavers spend much of the fall collecting and stuffing mud into the cracks between the branches that provide a framework for their lodge (leaving a mud-free air vent at the top of the lodge).  This mud as well as any snowfall that occurs during the winter help keep out the cold and retain the warmth that the resident beavers’ bodies radiate. 

A comparison of the (cooler) interior temperature of bank dens and that of open-water lodges confirms that the temperature of the substrate underlying a lodge also contributes to the air temperature of the chamber.

Lastly, heat produced by beavers raises the temperature of a lodge above that derived from the lodge substrate.

(Photo: beaver lodge on a morning cold enough to show “beaver breath” escaping through the air vent that runs up through the center of the lodge to its peak. Thanks to Kay Shumway for photo op.)

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Beavers Gathering & Caching Winter Food Supply

Beavers are busy reinforcing their lodges and repairing dams as the days shorten and temperatures fall.  Once these tasks are taken care of, they begin gathering and storing all of the food that they will need this winter, for once ice forms they will no longer have access to land.

Their winter food cache is placed as close to the entrance of their lodge as possible, as the inhabitants of the lodge will be swimming out to this pile frequently to obtain food.  After hauling branches and saplings to the lodge, the beaver dives down and jabs the butt end of the branch into the mud at the bottom of the pond.  Additional branches are woven into this base layer until eventually most caches weigh two or more tons. One can often see the pile’s top branches and leaves rising above the surface of the water. 

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Eastern Gray Squirrels Preparing For Winter

Eastern Gray Squirrels (Sciurus carolinensis) eat about two pounds of food per week.  Nuts and other seeds are at the top of the list, but fungi, berries, bird eggs and nestlings, tree buds and sap are also consumed.  Because they stay active in winter, Eastern Gray Squirrels must store food in the fall in order to survive the colder months, and this food must be viable for the duration of the winter.  They are what are called “scatter-hoarders” – they bury each nut separately, not all in one spot. After digging a hole 1-2 inches deep with its front paws, the squirrel places a nut in the hole and forcibly puts it in place by pounding it into the ground with its front incisors.  It then fills the hole with soil and covers it with leaves.  A combination of memory (experiments found that this works for about 20 minutes) and after that, scent, allows squirrels to relocate a portion of their cached nuts.

Hickory nuts are the food of choice for Eastern Gray Squirrels, in part because they have twice the calories of an average acorn.  They also store well over winter, as they don’t germinate until spring.  As the accompanying photograph shows, Eastern Gray Squirrels, before burying the nuts (in this case, Shagbark Hickory, Carya ovata), methodically remove the fragrant husks, leaving a pile of small pieces of husk on the ground. It’s likely this practice developed in order to prevent competitors from smelling, digging up and consuming the squirrel’s winter food supply.

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Unusual Beaver Activity

Beavers are known for their ever-growing incisors which allow them to cut trees down, eat the cambium (a nutritious layer just beneath the bark) and cut what’s left into pieces they are able to haul and use as building material for dams and lodges. More often than not, it’s straight forward work.

Occasionally not every step is taken – you can find standing trees that had the bottom three or four feet (as high as the Beaver could reach) of cambium removed without the trees being felled.  You can find de-barked logs that have been left where they fell and not carried or floated to the dam or lodge as construction material.  It’s also not unusual to find standing trees where several times a Beaver has attempted but failed to cut all the way through.

Recently John Twomey brought to my attention a tree felled by Beavers unlike any other I’ve ever seen:  one or more Beavers had cut down a Paper Birch and eaten the cambium layer, leaving the tree clean of bark.  At some point they cut into the tree every 18 inches or so, not quite severing the pieces, but leaving them connected by a core of wood that ran the length of the tree. If any readers have seen anything similar to this, or if you have an idea as to why Beavers would have cut the tree in this fashion, Naturally Curious would love to hear from you.  (Photo by Prentice Grassi of his sons investigating said tree earlier this spring.)

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Male Eastern Chipmunks Exploring Female Territories

Eastern Chipmunks breed twice a year, in March and in June.  If you’ve seen a chipmunk this spring, chances are it was a male, as males emerge several weeks before females.   When they first come above ground, males check out female territories.  When females appear they soon come into estrus, which lasts for roughly a week.  However, they are only receptive to males for about a seven-hour period during this week.  Outside of these seven hours, females will aggressively repel any advances.  When males sense that their timing is right, they indicate their interest and intention by waving their tail up and down.  This only occurs during the mating season – at all other times chipmunks only wave their tail horizontally back and forth!

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Beavers Foraging

Even in the coldest of winters, there is often a thaw around this time of year that frequently allows beavers to escape the cold (+/- 34°F) dark lodge where they reside during most of the winter.  Our most recent thaw was such that in many beaver ponds, ice didn’t even have to be broken in order for resident beavers to forage for food on land.

When beavers are confined to complete darkness (under the ice) their 24-hour circadian cycle extends to a 28 hour day. During this time beavers sleep for longer periods at a time and thus need less food.  As spring approaches and the days lengthen, the slightest exposure to daylight will reset the beaver’s biological clock back to the circadian cycle. (Leonard Lee Rue, Beavers)  (Photo by Alice Trageser)

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Woodchucks Fattening Up

This Woodchuck is doing what Woodchucks do this time of year – eating fast and furiously, and putting on fat equaling about a third of their weight (granted, an apple has only a tiny fraction of a gram of fat, but every bit helps).  Accumulation of fat is essential if they are to survive months of hibernation.  It’s not known what stimulates this increase in appetite, but most likely photoperiod (length of day) plays a part.

Soon these rodents will seek shelter in their winter burrows, where their heart rate is reduced from 100 beats per minute to 15 and their temperature drops from 96 F. degrees to 47 F. degrees.  During hibernation, they lose roughly 20% to 47% of their body weight.  Those Woodchucks not able to accumulate sufficient fat reserves may not survive the three or four months of hibernation that take place in the Northeast. (Photo by Erin Donahue)

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Beavers Feeding Young

In summer Beavers spend considerable time on land searching for, cutting and bringing vegetation back to their young in the lodge.  Their woody plant preference (they eat large amounts of herbaceous plants during the warmer months, but also some trees) tends towards the inner bark (cambium) of willow, aspen, maple, birch, cottonwood, beech, poplar, and alder trees. This beaver, however, has retrieved a Red Oak sapling for its offspring.

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Muskrats & Spatterdock

6-12-19 muskrat eating water lily flower bud1B0A0488Cattails, sedges, rushes, water lilies and grasses make up the bulk of a Muskrat’s diet although these aquatic rodents have been known to occasionally dine on fish, crustaceans and freshwater clams.

Muskrats typically don’t eat their food where they find it – they usually bring it out to a feeding platform in the water, which provides them with some protection from predators. However, they make an exception for Bullhead Pond-lily flower buds (Nuphar variegata), also known as Spatterdock, which they often devour on the spot wherever they find them (see photo). Beavers, Porcupines (yes, Porcupines can swim), White-tailed Deer and waterfowl also dine on the leaves, rhizomes, buds, flowers and seeds of Bullhead Pond-lilies.

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Porcupines Giving Birth

porcupine IMG_3096Towards the end of April/beginning of May, Porcupines give birth to one offspring. The newborn is covered with quills, but they are soft and enclosed in a sac, which protects the mother as she gives birth to her young. The young Porcupine’s eyes are open, and it is fully alert. Its quills harden within an hour. The Porcupine starts supplementing its mother’s milk with vegetation after the first two weeks, but isn’t completely weaned for four months.

During the day the young Porcupine stays hidden in a crevice or at the base of a tree near the tree in which its mother rests. Instinct takes over immediately in the face of danger, as it tucks its head down, turns its back to the predator and vigorously flicks its tiny, two-inch tail. When night falls, the mother and young Porcupine reunite. (Photo: days-old Porcupine)

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Male Woodchucks Out and About

2-22-19 woodchuck burrow IMG_0555Hibernation, the true slowing down of one’s metabolism (a Woodchuck’s body temperature drops from 99 degrees F. to 40 degrees F. and its heartbeat drops from 100 beats per minute to 4 beats per minute) is one way an animal conserves energy. Male and female Woodchucks use the energy they’ve conserved very differently in early spring.

At the end of February and in March, males arouse themselves about a month prior to the mating season and spend long periods visiting females and defending their territory. Muddy tracks and trails can be seen near their winter burrows (see photo) at this time of year. Females remain in their burrows in a state of hibernation, saving as much energy as possible for the birth and raising of their young. After confirming the presence of females on their territories, males return to their burrows for the next month or so, awakening along with the females in time for their mating season.

The timing of Woodchuck procreation is not a relaxed affair. It is quite precise, in fact, for very good reasons. If Woodchucks mate too early in the spring, their young won’t be able to find food once they are weaned. If they mate too late, their young won’t have the time necessary for putting on weight and storing fat before hibernation begins. Now is the time to look for signs indicating male Woodchuck activity near their winter woodland burrows.

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Beavers Breeding

2-6-19beaverimg_3683Beavers are in the middle of their breeding season, which means copulation takes place under the ice, undetected by human eyes, making information about their reproductive habits hard to come by. What is known about the breeding practices of North America’s largest rodent is that beavers form permanent breeding pairs and are monogamous through consecutive breeding seasons. Should a beaver’s mate die, a new one will take its place. In a colony, only the adult (individuals which are at least three years old) pair breeds. Mating usually takes place in January or February, and typically occurs at night in the water. Gestation is roughly 128 days and three or four kits are born in May or July.

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Eastern Gray Squirrel Diet Preferences

11-16-18 gray squirrel_U1A1563

The diet of Eastern Gray Squirrels is extremely varied. Depending on the season, buds, fruit (such as the pictured crabapples being consumed), maple and oak flowers, berries, seeds, fungi, the inner bark of maple and elm, insects, and young birds are eaten. However, nuts are by far the main component, which is reflected in their distribution; the range of Gray Squirrels coincides strikingly with that of oak and hickory forests. Especially during the colder part of the year, nuts, acorns and maple seeds, or samaras, that they have stored for winter consumption are the mainstay of their diet. (Research shows that Gray Squirrels recover 85% of the nuts they store.)

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A True Mystery Photo

11-2-18 flying squirrel tails_U1A1190A discovery recently brought to my attention has stumped this naturalist.   What you are looking at is a collection of Flying Squirrel tails lying within a 30-square-foot patch of ground adjacent to a stand of Eastern Hemlocks. For several days in succession, additional tails appeared each morning, eventually totaling 20 or more.

Flying Squirrels, both Northern and Southern, are part of many animals’ diet.  Among the documented predators are Great Horned Owls, Barred Owls, Screech Owls, Northern Goshawks, Red-tailed Hawks, Martens, River Otters, Weasels, Fishers, Red Foxes and Bobcat.  Many of these animals can gain access to the trees where the Flying Squirrels reside.  Others take advantage of squirrels foraging on the ground.

The puzzling part of this mystery is the large number of tails.  In cold weather (usually in winter, but we’ve had below-freezing nights recently), Flying Squirrels huddle together in tree cavities in an attempt to provide themselves with added warmth.  Did a foraging Fisher discover a communal den?  How did it manage to capture so many squirrels?  Did the survivors remain in the same cavity, only to be captured in subsequent nights?  So many questions that this naturalist cannot answer. Perhaps a reader can! (Thanks to John Quimby and Michael O’Donnell, who kindly shared their fascinating discovery with me.)

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Eastern Gray Squirrels Swimming

e-gray squirrel swimming by Erin 2_H6A2563 copy (002)Imagine coming upon a stick floating in a large pond only to discover the “stick” had a head and tail and was making a beeline for the shore.  The fact that an Eastern Gray Squirrel (Sciurus carolinensis) had paddled half a mile to get from one shore to the opposite shore of a pond shouldn’t have come as such a surprise, as this rodent has a long history of migratory swimming behavior, but it’s such an incongruous and unexpected event that it made my companion and me initially question our eyesight and then laugh out loud.

Historical reports suggest there have been many massive Eastern Gray Squirrel migrations in the United States, beginning in 1749 in Pennsylvania.   Records show the state paid three cents for each squirrel killed; over 640,000 squirrels were turned in for bounty.  One migration from Wisconsin in 1842 lasted four weeks and involved a half billion squirrels. Because of the numerous squirrel migrations, John James Audubon was erroneously convinced that the squirrels on the move were a separate species from the Eastern Gray Squirrel and gave them the scientific name Sciurus migratorius. (This proved to be inaccurate.)

During the 1800’s, thousands of squirrels would periodically move en masse across roads, fields and forests, and swim across lakes and rivers (including the Mississippi and Connecticut Rivers) in an effort to disperse. The consensus is that these mass movements were a response to local food conditions. They occurred mostly during the month of September following a year in which there was a large production of food (acorns).

The most recent mass migration of Eastern Gray Squirrels in eastern U.S. occurred in 1968, when a bumper crop of acorns in 1967 was followed with a corresponding bumper crop of young squirrels in 1968. By fall, as the first litter of the year left the nest, there was a severe shortage of food. As a result, massive numbers of acorn-eating squirrels dispersed in search of food.

One Eastern Gray Squirrel swimming across a New Hampshire pond does not a migration make, but it might not be a bad idea to keep an eye out for excessive numbers of paddling squirrels and/or road-killed rodents come September. (Photo by Erin Donahue)

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Red and White Baneberry Fruits Maturing

8-16-18 red and white baneberry-1While the flowers of Red (Actaea rubra) and White Baneberry (Actaea pachypoda) are quite similar (the flower head of Red Baneberry is more globular than the elongated head of White Baneberry), their respective fruits, the color of which gave them their common names, quickly distinguish these two species from each other.

White Baneberry produces white fruits commonly called “Doll’s eyes” due to the persistent remains of the flower’s stigma, which leaves a black dot on each fruit.  Red Baneberry’s shiny red berries also have these black dots, though they are not as apparent. All parts of both species are poisonous, with the berries being the most toxic part of the plant.

Seed dispersal is carried out by animals that have enough tolerance to feed on the berries. These animals include various mice, squirrels, chipmunks and voles, as well as a wide variety of birds and White-tailed Deer.

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Beavers Eating & Grooming

7-11-18 beavers 049A5253

This photograph conveys the essence of a beaver’s summer – eating and grooming… more eating, more grooming. During the summer months, beavers feed on non-woody vegetation (grasses, ferns, aquatic plants, etc.) 90% or more of the time. (During March/April and October/November, their diet switches to 60%-90% tree bark, and during the winter, bark from trees stored under water composes 100% of their diet.)

When beavers are not eating, much of their time during the warmer months is spent grooming, both themselves as well as each other.  Combing debris out of their coat (with the help of a split nail on both hind feet) and applying oily material from their anal glands to waterproof their fur consume much of their waking hours, both at night as well as at both ends of the day. (Castoreum, produced in castor sacs, differs from anal gland secretion, and is used primarily to mark territory.) (Thanks to Roger and Eleanor Shepard, and Sara and Warren Demont for photo op.)

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