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North American Tree Squirrel

(Family--Sciuridae, Sub-Family--Sciurinae) 

Tree squirrels are everywhere. They thrive in the country and in the city. Their acrobatics delight young and old. They are one of the most abundant mammals worldwide (except Australia) and they have been here for at least 50 million years.

The following lesson will open up the world of the tree squirrel to fifth grade students. Students will gain an appreciation for the marvelous way this small rodent is adapted to its life in the trees. Students will discover there is more to a tree squirrel than an animal to hunt, kill, cook, and eat.

North American Tree Squirrel
This tree squirrel is enjoying an acorn as it sits on a limb,
high in an oak tree in Ouachita County.

Research reveals that squirrels have lived and thrived on earth for at least the past 50 million years. Fossils show that squirrels were around during the Cenozoic Era when forests of seed and nut bearing trees began to cover the earth. The name, squirrrel, originated in ancient Greece. Squirrels were known by the Greek word , "skiouros," which translates as shade tails or is more loosely translated as: one who sits in the shadow of his tail. (Webster’s Third Dictionary -Unabridged , p.2217) There are approximately 270 species of squirrels worldwide. Squirrels are found on all continents except Australia. They are a member of the rodent (gnawing animal) family. Approximately 40% of all present day mammals are members of the squirrel family. There are three main types of squirrels: tree squirrels, flying squirrels, and ground squirrels . The most common tree squirrels of North America are the gray squirrel, the fox squirrel, and the red squirrel.

Tree squirrels are so named because they live in trees. Trees provide three basic needs for tree squirrels: water, food, shelter. Squirrels rarely drink water. They get most of their water from their food and dew. A squirrel’s diet includes: seeds, nuts, fruit, buds, shoots, bark, sap, insects, eggs, berries, and fungi (mushrooms). Squirrels can eat mushrooms that are poisonous to humans because the squirrel’s digestive tract is able to neutralize the poison in these mushrooms. Most of the items in a squirrel’s diet are found in or around trees. An urban squirrel may add scraps from trash such as bread, fruit, meat, and snack food to its diet. A squirrel’s diet is seasonal depending on what is available.

Squirrel’s are very active diurnal mammals that use a tremendous amount of energy in their daily life. The average squirrel eats about two pounds of food a week. This is a little over 100 pounds of food a year. Therefore, squirrels spend most of their life in the pursuit of food. "Animal ecologists have seen squirrels strip as many as 190 pine cones in one day." (McConoughey, p.21). Their long incisors must endure an enormous amount of wear as squirrels use them to crack nuts, bite off pine cones, crack seeds, and gnaw bark. These incisors grow continuously throughout the squirrel’s life at the rate of 6 inches per year.

Squirrels instinctively bury food (nuts, pine cones) in the fall to prepare for the winter. Squirrel’s have a good memory (brain the size of a walnut) but they also rely on their highly developed sense of smell to locate burried food. Squirrels add a scent to the nut by licking it or rubbing it against their fur before they bury it--to help them locate it months later. "They can smell a pine cone 12 inches beneath the snow." (McConoughey, p.21). In the winter a squirrel eats any food it can find--whether or not it was the squirrel that burried it. As squirrels do not find all the nuts they bury, they play an important part in reforestation.

Trees squirrels live in trees--either inside a hollow part of the tree or a leaf nest. Each squirrel claims a territory and marks it with his/her scent.. For protection squirrels usually build several smaller nests in addition to the main nest. They also build an escape hole in each nest. The nest provides protection from heat and cold, a refuge from enemies, a place to raise their young, and a storage site for food. Squirrels usually live alone in their nest. Exceptions are: wintertime when body heat is needed to keep warm, and when the female is raising her babies. Babies are born hairless and defenseless in a liter of about five. At eight weeks they are weaned and must acquire their own food. The male plays no part in the raising of the babies. An adult tree squirrel can weigh as much as seven pounds and has a life span of approximately six years.

Tree squirrels are well adapted to tree living. They have: strong muscular bodies--needed for their acrobatic lifestyle in the trees, well curved claws--to grip limbs and food, large eyes and ears--to ensure survival, eyes located high and on each side of their head--to give them a wide field of vision necessary for high speed travel through the trees, and a long bushy tail. This tail serves the squirrel as an umbrella, a blanket, a parachute, a natural balance, and a rudder. The tail makes it possible for squirrels to live in the trees.

Tree squirrels are not agressive animals and will flee rather than fight when threatened. Natural enemies of tree squirrels include: birds of prey, martens, weasels, snakes, foxes and dogs. Tree squirrels depend on their speed, heightened sense of smell, keen eyesight, protective coloration, and inborn caution to protect them.

  

Squirrel Nest
Tree squirrel leaf nest
Blanchard Springs, Arkansas

Pine Cones
Pine cones peeled by a tree squirrel determined
to eat the seeds inside.

Squirrel
Tree squirrel in a Hav-A-Heart trap ready to be relocated outside the city limits.
  

Squirrel Nest
Squirrel nest high in the trees in Ouachita County. 
Some people have wondered what type of big birds
build this kind of big nest.

Bibliography

Coldrey, Jennifer. The World of Squirrels. Milwaukee: Gareth Stevens Publishing, 1986.

Gove, Philip, ed. Webster’s Third Dictionary-unabridged. Springfield: Merriam-Webster Inc., 1991.

Grassy, John, and Keene, Chuch. First Field Guide Mammals. New York: Scholastic, 1998.

McConoughey, Jana. The Squirrels. Mankato: Crestwood House, 1983.

"Squirrel." Compton’s Encyclopedia, 1984 ed.

"Squirrel" Microsoft (r) Encarta (r) Encyclopedia, 1997ed.

"Squirrel" The New Book of Knowledge, 1986 ed.

"Squirrel" The World Book Encyclopedia, 1995 ed.

Project Author: Glenda Henley


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