Squirrels and Other Sciurids of Missouri

If you live anywhere in the United States, then squirrels are probably an extremely common sight. In fact, squirrels, or the family Sciuridae, inhabit almost every major land mass, except for Australia and Antarctica, though they have been artificially introduced by humans to Australia. There are 279 species total and between them they occupy nearly all habitats, from tundra to desert to rainforest (Brown et al. 2014). Some species thrive in urban environments as well, making them ubiquitously known in the human world. North America has long been considered the origin of this clade, but new evidence suggests it may actually be Eurasia (Rocha et al. 2016). There are sixty-six species in North America and seven species in the state of Missouri (Schwartz 2001; Whitaker 1996).

Squirrels come in a wide range of sizes, but are identifiable by their long bodies, large eyes, and soft fur. They have four digits of their forefeet and five digits on their hind feet (Brown et al. 2014). The popular conception of squirrels is a rodent with an extremely bushy tail, and the family name Sciuridae means “shade tail,” but this characteristic really only applies to aboreal species (Whitaker 1996). There are three basic types, which are not necessarily divided as such on the evolutionary tree:

• Tree squirrels: Naturally, these are the ones that can be seen running along tree branches. They have long, muscular limbs for climbing, large tails for balance, and big ears. They are mostly solitary, but may maintain loose relations with neighbors (Brown et al. 2014).
• Ground squirrels: The most social of the types, ground squirrels often be found in colonies, and live in undergound burrows. Their bodies are well-suited for digging: they have broad forefeet and short limbs. Tails are also short so as not to interfere with digging. Marmots are sometimes included in this category and sometimes on their own (Brown et al 2014; Whitaker 1996).
• Flying squirrels: These are the only nocturnal squirrels, which leads them to have larger than average eyes to take in the low light. They generally resemble regular tree squirrels, except for the glaring fact they have a gliding membrane, a loose flap of skin, from the wrist to heel on either side of the body. Their limbs are longer to accomodate them (Brown et al 2014; Whitaker 1996).

These three types are covered through five subfamilies, two of which are represented in Missouri species (Brown et al. 2014).

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Eastern Gray Squirrel (Sciurus carolinensis)

These tree squirrels are medium sized, around 14-21 inches including tail, and exist in the eastern half of the US and lower Canada. Though they naturally live in dense hardwood forests with bushy understories, they also thrive in urban parks containing large nut trees, making them one of the most high profile species in the area. They are mostly dirty gray in color, but the undersides are white and can have brown mixed in on the back, sides, head, feet and tail. Their eyes are rimmed with white and their bushy tail fur is tipped with it. 

Eastern gray squirrels do not hibernate, but are most active in the fall when nuts are ripening. Their diet strongly depends on the seasons, moving from buds to fruits to nuts, and more. Often individuals will have a favorite feeding site they take their food to; littered nut shells are clues to these sites. To store nuts, they carry the nuts 50-100 feet away from the source tree and bury them in the ground. Gray squirrels live in very loose communties and so the stored nuts are shared by the communtiy. They are prey to medium-sized mammalian carnivores like coyotes and bobcats; owls, hawks, and snakes. 

In the wild, eastern gray squirrels live approximately 6 years. Peak mating seasons start in late December and late May. Females give birth to a litter of 1 to 8, and the male takes no part in the rearing process. Young mature in less than a year; the tail becomes bushier with age (Schwartz 2001).

Fox Squirrel (Sciurus niger)

These are the nation’s largest tree squirrels at 19-29 inches long (Whitaker 1996). Only the rufiventer subspecies is found in Missouri, which is predominantly reddish-yellow in color. The back and sides can be heavily tinted gray, however. Their habitats overlap with gray squirrels, but these prefer woodlands on higher ridges. As such, Osage orange fruits and corn make up more of their diet because they are more common there; otherwise their diets are similar (Schwartz 2001). 

Fox squirrels mostly spend one year close to one specific tree. They prioritize denning in tree cavities, but will also make leaf nests, or have both at the same time, but they are replaced as they get damaged every few months or years (Schwartz 1996; Whitaker 1996). Fox squirrels take care to groom themselves regularly, but do not apply the same hygiene to their nests. They are active year-round, and are generally solitary; however some may den in groups during winter (Whitaker 1996). Fox squirrels can live up to 7.5 years (Schwartz 2001).

Eastern Chipmunk (Tamias striatus)

Chipmunks are small ground squirrels around 8-12 inches in length, but do occasionaly climb trees for food and to escape predators. They are primarily brown on the back and feet and buff to white on the belly. Five stripes run down their backs; the outside pairs sandwich a white stripe each. The tail is not particularly bushy and is black and rusty with light fringing; it makes up about a third of total length. Three dark stripes run along each side of the face. Their ears are round and upright and their legs are moderately short. Though everywhere in Missouri, they are most common in the Ozark Highland in timber borderlands. Their most common vocalization is string of very loud, rapidfire chips. (Schwartz 2001)

Chipmunks mainly eat nuts, berries, and seeds, and the occasional small animal, but favor acorns and hickory nuts (Whitaker 1996). Famously they have specialized cheek pouches above each front foot used to store food, which if not eaten they proceed to store underground. They nest in burrows that range in complexity, but all consisting of a hidden entrance and an enlarged chamber about 2.5 feet underground for both food storage and nesting. Predators include small Carnivora, hawks, owls, and snakes (Schwartz 2001)

These squirrels do hibernate to varying degrees in the winter, usually ending in late February/ early March. Food is stored under the leaves that make the nest for easy access, and they wake every two weeks to eat (Schwartz 2001; Whitaker 1996). Females give birth between April and May and between July and August; this species is unique in being able to breed twice in one year. The average litter is 4 to 5 young. Wild chipmunks live 2 to 5 years (Schwartz 2001).

Woodchuck (Marmota monax)

Also known as a groundhog, these are the bulkiest of the Missouri squirrels, measuring between 16 and 32 inches long and weighing in up to 14 pounds (Schwartz 2001; Whitaker 1996). The tail composes 3.75 to 7.5 inches of that length, and it is rather flat. They have a large head with small ears and a large body with short limbs. Their upper inscisors peek out when the mouth is closed. Individual woodchucks are varying mixes of grey, black, white, tan, and reddish tints, but the top of the head and back are darker than the undersides. The legs gradient to black feet. Woodchucks are common throughout Missouri except in the Mississippi Lowland where the ground is unsuitable for digging. They prefer timber and brush areas in winter and open grasslands in summer (Schwartz 2001).

Their diet consists of leaves, flowers, field and garden crops, grasses, herbs, and fruits like the pawpaw.  Rarely they eat small invertebrates or eggs. Occassionally they will climb trees for fruit. Woodchucks are also often seen eating asphalt gravel for its salt content. They have similar predators to other squirrels but those predators mainly take juveniles due to the woodchucks’ size (Schwartz 2001). When threatened they will whistle, hiss, chatter teeth, or growl (Whitaker 1996).

Woodchucks live in burrows individually or in small family groups. The main entrance is easily spotted because of the pile of dirt in front from digging, also used as a lookout or sunning point. The number of chambers and side entrances vary. Woodchucks do hibernate in their nests and rarely come out before the end of winter. The hibernation period starts late October and ends the beginning of February, hence Groundhog’s Day (Schwartz 2001). 

Breeding season starts mid-February and females give birth to an average of 4-5 young. Woodchucks are integral to their ecosystems because their vacated burrow systems become homes to skunks, rabbits, and many other mammals (Schwartz 2001). 

Thirteen-Lined Ground Squirrel (Spermophilus tridecemlineatus)

This squirrel is small and slender, measuring 7-12.5 inches long. It gets its name from the 7 light and 6 dark stripes on its back for camouflage, though the exact numbers can vary. To accomodate its digging lifestyle it has large claws and small ears. The thirteen-lined ground squirrel is uncommon in Missouri and only occurs in the northern and western prairies. One typical stance it engages in is the picket pin, where it stands very upright on its hind legs with front paws pressed into the belly.

It prefers open fields but will occasionally live in slightly covered areas. The main entrance of their burrows, which is inconspicuous because they scatter the dirt using their cheek pouches, leads to a vertical shaft and utilizes right angles to lead to nests, hibernation chambers, storehouses, etc. The burrows can be 20 feet deep. Although relatively solitary and antagonistic toward one another, they usually group burrows into colonies.

Thirteen lined ground squirrels are omnivorous, going after seeds, fruits, nuts, and other low plant matter as well as insects, earthworms, and small/young vertebrates; only the seeds and nuts are stored. Their predators are the typical Scuiridae predators: Carnivora, hawks, owls, and snakes. 

These squirrels are one of the few that enter true hibernation. For a period as long as late summer to early April, squirrels retire to their burrows, plugging the entrances, and rarely come out until the spring when the ground is thawed. Breeding occurs only a few weeks after waking. During the summer their above ground activity is heavily dependent on the brightness outside, thus being most active midday when it is sunny (Schwartz 2001). 

Franklin’s Ground Squirrel (Spermophilus franklinii)

Franklin’s ground squirrel is larger than the thirteen-lined ground squirrel at 13.75-16.5 inches long. Also known as the gray ground squirrel, its fur is dirty gray with black speckles, with a lighter underside, darker feet, and yellowish rump. Like other ground squirrels, it too has large claws, small ears, and a less bushy tail than tree squirrels. They also occupy the northern and western prairies of Missouri, but prefer timber borderlands or other semi-covered or marginal habitats. While their burrows are similar to thsoe of thirteen-lined ground squirrels, they are larger, deeper, and more hidden. They make colonies of around 11 individuals, and they change sites every year or so (Schwartz 2001).

Their diet consists of mainly nuts, seeds, fruits, and green vegetation, and one third or so includes insects, frogs, small birds and rabbits, and even other ground squirrels. Their major predators are those capable of digging, including foxes, weasles, and badgers, for these squirrles spend up to 90% of their lives underground (Schwartz 2001; Whitaker 1996). 

Franklin’s ground squirrels enter hibernation around the end of October; their reemergence in early April is signaled by their resumed musical whistling. Sometimes they will hibernate in groups for warmth. Their above-ground activity is also strongly governed by the strength of daylight. Reproduction starts soon after reemergence, garnering an average of 7 young per litter (Schwartz 2001).

Southern Flying Squirrel (Glaucomys volans)

As Missouri’s only flying squirrel, this species is readily identifiable by the loose flying membrane extending from the wrists to ankles. Cartilaginous spurs protrude from the wrists to allow greater surface area for the membrane when extended. They have big ears and eyes and long whiskers. The tail is bushy and broad for use as a rudder in “flight.” The fur is very soft. The dorsal side is gray or brownish while the underside is pale; along the sides of the membrane is a black stripe. They molt into lighter colors for winter (Schwartz 2001). They do not hibernate but may enter torpor, a mild version of hibernation, at cold temperatures (Whitaker 1996).

Southern flying squirrels are distributed throughout Missouri but mostly in oak-hickory forests like the Ozark Highlands. Occasionally they survive in urban environments in roofs and birdhouses. Because they are nocturnal, they are rare sightings. They nest in tree cavities and can have multiple dens for emergencies that are kept clean for hygiene, which assists smooth gliding. Females can be territorial but in the winter groups of up to 19 individual squirrels can congregate for warmth. Their favorite foods are acorns, hickory nuts, and corn, but also eat other nuts, seeds, and fruits. They will also eat insects and bird eggs, and in the winter time, tree buds and bark. They store nuts in their dens or other cracks in trees. They can fall prey to both diurnal and nocturnal predators (Schwartz 2001).

Flying squirrels fly, or rather glide, by outstretching their limbs and varying slack on the flying membrane. A typical glide is around 20 to 30 feet long between 30 and 50 degrees down, but the record is 270 feet. They are capable of making 90 degree turn to avoid obstacles in gliding. They can also adeptly run along branches and forage on the ground; however they cannot swim well (Schwartz 2001). 

Works Cited

Brown, Emily McBride, Alexandra Michelle Peri, and Nicole Ann Santarosa. “Sciuridae.” Animal Diversity Web. Regents of the University of Michigan, 2014. Web. 22 Nov. 2016.

McRae, Thaddeus R., and Steven M. Green. “Joint Tail And Vocal Alarm Signals Of Gray Squirrels (Sciurus Carolinensis).” Behaviour 151.10 (2014): 1433-1452. Academic Search Complete. Web. 15 Dec. 2016

PARDO, MICHAEL A., SCOTT A. PARDO, and WILLIAM M. SHIELDS. “Eastern Gray Squirrels (Sciurus Carolinensis) Communicate With The Positions Of Their Tails In An Agonistic Context.” American Midland Naturalist 172.2 (2014): 359-365. Academic Search Complete. Web. 15 Dec. 2016.

Rocha, R. G., et al. “Independent Reversals To Terrestriality In Squirrels (Rodentia: Sciuridae) Support Ecologically Mediated Modes Of Adaptation.” Journal Of Evolutionary Biology 29.12 (2016): 2471-2479. Academic Search Complete. Web. 16 Dec. 2016.

Schwartz, Charles Walsh., and Elizabeth Reeder Schwartz. “Gnawing Mammals.” The Wild Mammals of Missouri. 2nd ed. Columbia: U of Missouri, 2001. 131-76. Print.

United States of America. Missouri Department of Conservation. A Summary of Missouri Hunting and Trapping Regulations. Jefferson City, MO: Missouri Department of Conservation, 2016. Missouri Department of Conservation. State of Missouri, 1 Mar. 2016. Web. 14 Dec. 2016.

Whitaker, John O., Jr. “Squirrels.” National Audubon Society Field Guide to North American Mammals. New York: Knopf, 1996. 408-502. Print.

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