Squirrels

Eastern Gray Squirrel:

(Sciurus carolinensis)

Conservation status:

Least Concern

Origin:

Native to the eastern half of North America, grey squirrels were first introduced to Britain in the 1870s and are now widely distributed across the United Kingdom.

Lifespan:

Mean life expectancy for a gray squirrel at birth is 1-2 years; the average life span of an adult is closer to 6 years. Records for maximum life span are 12 years in the wild and 20 years in captivity.

Size:

17-20″

1 – 1 ½ lbs.

Diet:

Eastern gray squirrels eat a range of foods, such as tree bark, tree buds, berries, many types of seeds and acorns, walnuts, and other nuts, and some types of fungi found in the forests, including fly agaric mushrooms (Amanita muscaria).

Activity:

Most active just after dawn and just before dusk.

Reproduction:

Eastern gray squirrels can breed twice a year.

Younger and less experienced mothers normally have a single litter per year in the spring.

Their breeding seasons are December to February and May to June, though this is slightly delayed in more northern latitudes.

Eastern gray squirrels exhibit a form of polygyny, in which the competing males will form a hierarchy of dominance, and the female will mate with multiple males depending on the hierarchy established.

Normally, 1 to 4 young are born in each litter, but the largest possible litter size is eight.

The gestation period is about 44 days.

The young are weaned around 10 weeks, though some may wean up to six weeks later in the wild.

They begin to leave the nest after 12 weeks, with autumn born young often wintering with their mother.

Only 1 in 4 squirrel kits survives to one year of age, with mortality around 55% for the following year.

Mortality rates then decrease to around 30% for following years until they increase sharply at eight years of age.

Extra facts:

As in most other mammals, communication among eastern gray squirrel individuals involves both vocalizations and posturing.

The species has a quite varied repertoire of vocalizations, including a squeak similar to that of a mouse, a low-pitched noise, a chatter, and a raspy “mehr mehr mehr”.

Other methods of communication include tail-flicking and other gestures, including facial expressions.

Tail flicking and the “kuk” or “quaa” call are used to ward off and warn other squirrels about predators, as well as to announce when a predator is leaving the area.

Squirrels also make an affectionate coo-purring sound that biologists call the “muk-muk” sound. This is used as a contact sound between a mother and her kits and in adulthood, by the male when he courts the female during mating season.

The use of vocal and visual communication has been shown to vary by location, based on elements such as noise pollution and the amount of open space. For instance, populations living in large cities generally rely more on the visual signals, due to the generally louder environment with more areas without much visual restriction. However, in heavily wooded areas, vocal signals are used more often due to the relatively lower noise levels and a dense canopy restricting visual range.

 

Eastern Fox Squirrel:

(Sciurus niger)

Conservation status:

Least Concern

Origin:

The fox squirrel’s natural range extends throughout the eastern United States, north into the southern prairie provinces of Canada, and west to the Dakotas, Colorado, and Texas. They are absent (except for vagrants) in New England, New Jersey, most of New York, as well as northern and eastern Pennsylvania. They have been introduced to both northern and southern California, Oregon, Idaho, Montana, Washington, and New Mexico.

Lifespan:

In captivity, fox squirrels have been known to live 18 years, but in the wild most fox squirrels die before they become adults. Their maximum life expectancy is typically 12.5 years for females and 8.5 years for males.

Size:

18-27″

1 ½ – 2 ½ lbs.

Diet:

The fox squirrel eats acorns, hickory, walnut, beech, mulberry and hawthorne seeds. It also eats green shoots and buds, fruits, berries, corn, insects, moths and beetles. Nuts are stored for use in the winter. The fox squirrel locates its stashes using its keen sense of smell.

Activity:

Most active just after dawn and just before dusk

Reproduction:

Eastern fox squirrels can breed twice a year.

Younger and less experienced mothers normally have a single litter per year in the spring.

Their breeding seasons are December to February and May to June, though this is slightly delayed in more northern latitudes.

Eastern fox squirrels exhibit a form of polygyny, in which the competing males will form a hierarchy of dominance, and the female will mate with multiple males depending on the hierarchy established.

The average litter size is 3, but can vary according to season and food conditions.

The gestation period is about 44 days.

Eastern fox squirrels are weaned between 12 and 14 weeks but may not be self-supporting until 16 weeks.

Juveniles usually disperse in September or October, but may den either together or with their mother during their first winter.

Only 1 in 4 squirrel kits survives to one year of age, with mortality around 55% for the following year.

Mortality rates then decrease to around 30% for following years until they increase sharply at eight years of age.

Extra facts:

Fox squirrels are strictly diurnal, non-territorial, and spend more of their time on the ground than most other tree squirrels. They are still, however, agile climbers.

They construct two types of homes called “dreys”, depending on the season. Summer dreys are often little more than platforms of sticks high in the branches of trees, while winter dens are usually hollowed out of tree trunks by a succession of occupants over as many as 30 years. Cohabitation of these dens is not uncommon, particularly among breeding pairs.

Fox squirrels will form caches by burying food items for later consumption. They like to store foods that are shelled and high in fat, such as acorns and nuts. Shelled foods are favored because they are less likely to spoil than non-shelled foods, and fatty foods are valued for their high energy density.

They are not particularly gregarious or playful, in fact they have been described as solitary and asocial creatures, coming together only in breeding season.

They have a large vocabulary, consisting most notably of an assortment of clucking and chucking sounds, not unlike some “game” birds, and they warn the listening world of approaching threats with distress screams. In the spring and fall, groups of fox squirrels clucking and chucking together can make a small ruckus. They also make high-pitched whines during mating. When threatening another fox squirrel, they will stand upright with their tail over their back and flick it.

They are impressive jumpers, easily spanning fifteen feet in horizontal leaps and free-falling twenty feet or more to a soft landing on a limb or trunk.

 

Southern Flying Squirrel:

(Glaucomys volans)

Conservation status:

Least Concern

Origin:

The southern flying squirrel is found throughout the eastern United States, from Maine south to Florida and west from Minnesota south to Texas.

Lifespan:

The life expectancy of flying squirrels in the wild is about 6 years, but flying squirrels can live up to 15 years in captivity. The mortality rate in young flying squirrels is high because of predators and diseases.

Size:

8-10″

Typically weighing about 2 ½ oz.

Diet:

The southern flying squirrel feeds on fruit and nuts from trees such as red and white oak, hickory and beech. They store food, especially acorns, for winter consumption. They also dine on insects, buds, mushrooms, mycorrhizal fungi, carrion, bird eggs and nestlings and flowers.

Activity:

Most active just after dawn and just before dusk

Reproduction:

Both in the wild and in captivity they can produce two litters each year (with 2–7 young per litter).

The gestation period is approximately 40 days.

Young are born without fur or any capabilities of their own.

Their ears open at 2 to 6 days old, and fur grows in by 7 days.

Their eyes do not open until they are 24–30 days old.

Parents wean their young 65 days after they are born.

The young then become fully independent at around 120 days of age.

Extra facts:

Southern flying squirrels show substantial homing abilities, and can return to their nests if artificially removed to distances of up to a kilometer. Their home ranges may be up to 40,000 square meters for females and double that for males, tending to be larger at the northern extreme of their range.

Flying squirrels do not actually fly, but rather glide using a membrane called a patagium.

From atop of trees, flying squirrels can initiate glides from a running start or from a stationary position by bringing their limbs under the body, retracting their heads, and then propelling themselves off the tree.

It is believed that they use triangulation to estimate the distance of the landing area as they often lean out and pivot from side to side before jumping.

Once in the air, they form an “X” with their limbs by spreading their long arms forward and out and their long legs backward and out, causing their membrane to stretch into a square-like shape and glide down at angles of 30 to 40 degrees.

They maneuver with great efficiency in the air, making 90 degree turns around obstacles if needed.

Just before reaching a tree, they raise their flattened tails that abruptly changes their trajectory upwards, and point all of their limbs forward to create a parachute effect with the membrane in order to reduce the shock of landing.

The limbs absorb the remainder of the impact, and the squirrels immediately run to the other side of the trunk or to the top of the tree in order to avoid any potential predators.

Although graceful in flight, they are very clumsy walkers and if they happen to be on the ground in the presence of danger, they will prefer to hide rather than attempt to escape.