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Posts tagged “Sciurus carolinensis

Wing Prints In The Snow

2-7-19 gray squirrel kill_U1A2844Rarely have I had the good fortune to come upon a predator dining on its prey, but in this case, luck was with me. Seconds after I spotted a Red-tailed Hawk on the ground working on something it noticed me and flew away, perching within sight so as to keep an eye on its recent kill. This sighting eliminated some of the mystery of the story written in the snow. Wing prints would have revealed that the predator was airborne, and the wingspread might have narrowed the list of potential hawks/owls that it could have been, but determining the species would have been challenging without a sighting.

Although smaller rodents (voles, mice, etc.) make up a greater percentage of a Red-tail’s diet than larger ones, Gray Squirrels (whose remains are visible and were still warm) are consumed. The large numbers of Gray Squirrels on roadsides last fall reflected a booming population which most likely has provided ample food for many predators this winter, including this hawk. Interestingly, fur from the tail had been removed prior to the bird’s directing its attention to the internal organs of the squirrel. A quick retreat by this curious naturalist hopefully allowed the Red-tail to return to its meal.

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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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Gray Squirrel Dreys

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With most deciduous trees having lost their leaves, squirrel nests, or dreys, are more noticeable. Red Squirrels, Eastern Gray Squirrels and Flying Squirrels all build dreys. Those of the Red Squirrel are round, grassy balls, 8” – 10” in diameter. In contrast, Gray Squirrel nests are usually larger and made of sticks and leaves. Flying Squirrel dreys are so high that they are rarely observed.

The dreys most commonly seen are made by Gray Squirrels. Usually 30 or more feet high, these shelters are typically built near the main trunk of the tree, in a crotch where several small branches meet, or on a strong, thick limb. Construction takes place in the summer or early fall, before trees have formed the abcission layers that cause leaves to separate and fall from branches. Therefore, the leaves on a drey’s branches tend to remain for quite some time, forming an effective water-shedding outer layer.

Branches are loosely woven into a foot-wide hollow sphere. The drey is lined with insulating grass, moss, leaves, and shredded bark. Usually there is one entrance/exit hole, facing the trunk (so as to keep rain out). Often squirrels build two dreys, giving themselves another shelter option should one nest be disturbed by a predator or overrun with parasites.

A drey is usually inhabited by one squirrel, but two are known to occupy a single drey in order to keep warm in the winter. Gray Squirrels give birth in late winter and again in the summer. A more protective tree cavity usually serves as a nursery in the winter, and the drey in summer. The average drey is only used for a year or two before it is abandoned.


Red Squirrels Dining on Black Walnuts

1-4-15 black walnut 145The method in which a nut has been opened depends on both the species of nut as well as the species of animal that opened it. To complicate things further, it can be difficult to ascertain who opened a nut as a given species, such as the Red Squirrel, often has more than one way of opening a nut. However, a given squirrel usually chooses one way to open a nut and consistently uses that method, so that if you come upon a pile, or midden, of nuts eaten by a Red Squirrel, the nuts will most likely all have been opened in the same way.

The beveled edges on the hole in the pictured Black Walnut, the fact that it was opened from both sides (leaving the dividing rib between the two sides intact), and the central location of the holes are indications that a Red Squirrel dined on the nutmeat. The chewing of open, jagged holes on either side of a nut is a Red Squirrel’s most common method of opening a nut. Gray Squirrels tend to remove the entire side of a walnut, as opposed to chewing a hole in it.

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Rodents Recycling

3-13-15  gray squirrel 001Bones, antlers, skulls, turtle shells – all are recycled relatively quickly by rodents seeking a source of minerals, particularly calcium and phosphorus. All rodents possess four incisors, two in the front of the upper jaw and two opposite these, on the bottom jaw. These incisors, unlike other teeth, never stop growing. By gnawing on hard objects such as bones, rodents keep their incisors paired down. If an incisor is broken or lost, the opposing incisor will continue growing in a circle, having nothing to grind against, causing the rodent to die of starvation or from having its brain pierced (through the roof of the rodent’s mouth) by the ever-growing incisor. In this photograph, a gray squirrel is obtaining minerals and sharpening its incisors on a moose skull that a human wedged into the crotch of a tree.

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Gray Squirrels Caching Nuts

9-26-14 gray squirrel with nuts 015Many species of squirrels, including the red squirrel, are “larder hoarders.” Each individual stores its food in one central area that it defends aggressively against invaders. Eastern gray squirrels, however, are “scatter hoarders,” collecting and burying one nut at a time throughout home ranges up to 7 acres in size. It has been estimated that up to 25 percent of the nuts that gray squirrels cache are stolen by other gray squirrels. Researchers have found that gray squirrels engage in “deceptive caching.” Carrying a nut, a squirrel will repeatedly dig a hole and then fill it in, without depositing the nut. They also will cover a spot with leaves, even though they have not buried anything in this location. Where gray squirrel densities are high, the squirrels often keep a cache in its original location for only about three days before moving it to a new location.

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Discerning Eastern Gray Squirrels

1-3-14 gray squirrel2 029In the fall, Eastern Gray Squirrels bury individual acorns from Red and White Oaks to sustain themselves through the winter. The acorns of Red Oaks have delayed germination – they can be stored up to six months before they start germinating. The acorns of White Oaks, however, have no such dormancy, and begin to germinate in the fall, soon after they fall from the tree. Once acorns sprout, they are less nutritious, as the seed tissue converts to the indigestible lignins that form the root. Gray Squirrels, as a means of “long-term cache management,” selectively remove the embryos from White Oak acorns (but not from Red Oak acorns) before burying them. Germination is prevented, and the storage viability of the White Oak acorns is extended by six months, equaling that of the Red Oak acorns.

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