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Rodents

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

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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

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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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Happy Groundhog Day !

2-2-18 woodchuck IMG_2381The Woodchuck, or Groundhog, is one lucky creature, considering past practices. The observation of “Groundhog Day” originated in the mid-1800’s, and by the late 1800’s and early 1900’s the celebration consisted of feasting on this rodent. A formalized hunt took place and participants then dined on Groundhog (which purportedly tastes like a cross between chicken and pork) and drank Groundhog punch. Since then, the Groundhog has evolved into a forecaster of weather, rather than a meal.

While New England Woodchucks are curled up in their hibernacula,  Punxsutawney Phil is busy seeing if he can see his shadow today (in which case we’re in for six more weeks of winter) or whether cloudy skies will prevent that from happening and spring is right around the corner. I’d bet on the former.

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What Goes On Beneath Our Feet In Winter

Alfred's mouse2 2018-01-16 20.39.08 (003)It’s fairly unusual to see Deer or White-footed Mice, especially in the winter – they are nocturnal and they spend much of their time in the airspace under the snow next to the ground known as the subnivean layer. (A blanket of snow traps the earth’s heat, which melts the bottom of the snow, creating this layer of space.) Here both Deer Mice and White-footed Mice travel extensively, protected from both the cold (it stays within a degree or two of 32 F. regardless of outside temperature) and the eyes of predators. On cold winter days, groups including both species of mice keep warm by huddling in a common nest. (Photo of White-footed/Deer Mouse – extremely difficult to tell the difference by sight – by Alfred Balch.)

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Porcupine Trails

1-12-18 mystery photo 049A2042Porcupines are forced to exert a lot of effort if they are in need of food and the snow is deep. Unlike many rodents that are light enough to travel on top of the snow, Porcupines must plow their way through it. Their weight, short legs, and bare footpads make traveling in snow challenging, to say the least.

If the snow is deep, the winter ranges of Porcupines are considerably smaller (18 acres in one research study) than their summer ranges (160 acres in same study).  Because of the energy needed to travel through the snow, Porcupines usually feed just a short distance from their winter dens, more often than not within 200 feet. Their feeding trails from rocky or hollow tree dens to their woody food sources (often Eastern Hemlock-note bits of branches on snow in photo, American Beech and Sugar Maple), are very distinctive. They are used every night when Porcupines leave their dens to feed and again several hours later when they return.  These trails become well marked with urine, and less frequently with scat and quills. (Photo insert: Porcupine rock den entrance)

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Beavers Breaking Ice

11-13-17 beaver and ice IMG_4410

We’re right on the verge of when beavers will no longer be able to smell fresh air, see the sun and obtain fresh bark. Until the temperature drops to around 16 degrees F. they continue to break through the thin ice covering their pond. Once the temperature remains in the teens or lower for several days, they no longer try to break through the ice and are sealed under it until spring, unless there’s a mid-winter thaw.

Once beavers are confined by the ice, their activities outside the lodge are minimal. Beavers leave their lodge in winter primarily for three reasons: 1) to swim out to their winter food supply pile and retrieve a branch which they bring back into the lodge to eat, 2) to defecate in the water, and 3) to mate in January or February. Other than these excursions, they spend most of their days in the dark, enduring life in a lodge that has a temperature of about 34 degrees F. (Thanks to Kay and Peter Shumway for photo op.)


Beavers Preparing For Winter

9-12-17 beaver2 20160905_5707The lazy, hazy days of summer are dwindling, and beavers’ internal clocks are telling them it’s time to batten down the hatches and prepare for several months of life below the ice. This entails adding a significant amount of mud to the outside of their lodge. The mud freezes and creates an impenetrable barrier between them and predators such as coyotes that, thanks to ponds being frozen, will have access to beaver lodges. This mud is anchored by the addition of debarked branches and logs that have provided the beavers with meals of cambium during the summer.

A beaver can transport its own weight in material (roughly 45-60 pounds). Retrieving debarked pieces of wood in many cases involves carrying them over both land and water, using only jaws and sometimes a shoulder for support.  A beaver’s short, muscular neck and its powerful lower jaw muscles make this possible. Try lifting one of the larger logs on a lodge or beaver dam sometime. Then imagine carrying it any distance in your mouth with no assistance from your hands. (This feat rivals that of a moose carrying two 25 – 30 pound antlers around for several months.) While there are recorded cases of beavers felling trees 150 feet tall and 5 feet in diameter, logs of this size are not used as building material for dams and lodges, but rather the bark and upper branches provide them with food.  (Thanks to Roger and Eleanor Shepard and Sara and Warren Demont for photo op.)


The Varied Diet of Muskrats

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Muskrats are primarily herbivorous. The majority of their diet consists of the tubers, roots, stems, leaves and fruit of a variety of aquatic and terrestrial plants, particularly those of bulrush, cattail and arrowhead. A diet of high fiber is possible because of bacterial fermentation which takes place in their intestines. The digestion of many herbivores is aided by bacteria, but many plant-eaters are restricted in what they can eat because they are unable to change their diet without killing the bacteria. Muskrats, however, can and do consume large amounts of meat (frogs, fish, turtles, crayfish, etc.) and still maintain a healthy population of fiber-digesting bacteria. (Thanks to Jeannie Killam for photo op.)


Muskrats Busy Feeding Young

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Birthing time for Muskrats is late April/early May, so this year’s young are roughly a month old. Weaning begins now and young Muskrats, who have been able to swim since they were two weeks old, begin foraging for themselves. Parents continue to supplement their offspring’s diet during this transition.  Although Muskrats are omnivores, the majority of their diet consists of the roots, stems, leaves and fruits of aquatic vegetation. However, when you’re feeding half a dozen offspring, you harvest whatever is available, including bedstraw (see photo).

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Woodchucks Active

3-15-17 woodchuck burrow IMG_0618Our recent snowstorm will make it a bit more challenging for male Woodchucks intent on mating, for they must work their way up through a foot or more of snow upon wakening. In March and April they come out of hibernation having lost 20 – 40 percent of their weight over the winter. Even so, sex is the driving force, not food, which is fortunate, as there is little for them to eat this early in the spring. Males dig their way out of their burrows and head straight for the burrows of females.   After mating, the female goes back to sleep for several weeks and the male returns to his burrow and does the same. Snow makes these tunnels much more obvious and thus easier to find, as dirt is scattered around their entrances. Equally obvious are the muddy trails males leave when in search of females.

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Eastern Chipmunks Emerging & Mating

3-13-17 e. chipmunk IMG_2353

All winter long, Eastern Chipmunks have been intermittently napping and running to their underground larder to snack every week or two. As spring approaches, the timing of their emergence above ground is affected by the weather, even though their tunnels are 18” – 36” below the surface. Within the last week chipmunks have been seen above ground.  One would think they must be in a state of confusion, given the erratic weather we’ve experienced this spring.

Chipmunks waste no time once they are active.  Most adult females are in breeding condition when they emerge (as opposed to males, which are in a state of constant readiness) and mate within a week. This involves 10-30 couplings within about a 6-7 hour receptive period.  In a month or so, the results of these efforts will be born.

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