The Effect of Approaching Humans on Squirrel Behavior
Squirrels are very interesting animals to study and can provide important information about animal behavior. They are known to some scientists as "living fossils" because they closely resemble their prehistoric relatives. (Emry and Thornington 1984, 8). Because their size allows them to be seen easily and their habitats are readily observable, squirrels are excellent test subject. In addition to this, they follow a daily cycle that coincides with our own human cycle. (Sherma and Morton 1979, 50) Because squirrels adapt quickly, it is possible to study this group of mammals in order to relate to other types of mammals. (Steele and Koprowski 2001, 1) Squirrels are a large group, with many types of appearances and differing habits. (Whitaker Jr. 1980, 370As a group, squirrels are easy to identify. This is one reason they make good study models. However, it can be difficult to identify one individual squirrel from each other. (Orr 58)
North American ground and tree squirrels have become increasingly adapted to the urban life of college campuses (Jones and Birney 1988, 166). Here at Miami University, we are surrounded by squirrels. One can hardly walk outside without seeing a squirrel. Because of this, we thought it would be interesting to see just how close one can come to a squirrel before the squirrel becomes frightened and runs. Through our research we seek to discover two things. Our first goal is to evaluate whether a significant difference in approachability exists between the squirrels found in the more populated areas of Main campus compared to those located on the less populated areas of Western campus. Our second objective is to determine what effect, if any, different manners of approach have on the distance we can come to a squirrel. We hope to answer the following questions: Will squirrels on Main campus allow a person to come closer than those on Western Campus or vice versa? Does the style in which you approach a squirrel have a direct affect on how close one may get to it? If so, what would be the most effective way in which to approach a squirrel, so that one might come as close to it as possible?
Our hypothesis is that the squirrels living in the more populated area of campus will generally be more approachable, possibly letting people approach within three feet. The squirrels inhabiting Western campus will be more inclined to flee when a researcher is within four to six feet of it. This belief is due to the fact that squirrels are exposed to fewer people on Western campus. The squirrels on main campus generally have more people walking around them. We also believe that we will be able to most closely approach the squirrels by walking rather than by running or by crawling. We believe the squirrels will feel the least threatened by a person who is walking. The speed of someone running may frighten the squirrel or cause it to think that it is being chased. Crawling may bear to close a resemblance to a predator stalking its prey, thus causing the squirrel to think that it is being stalked.
An alternate hypothesis is that we will be able to most closely approach the squirrels by crawling. When crawling, one may appear smaller, being lower to the ground, and thus less threatening to a squirrel.
Habitat and Foraging
Squirrels make their homes mostly above ground, in the trees. (Burt and Grossenheider 1980, 119) These trees are providers of food as well as shelter. Some squirrels inhabit crevices in the tree itself and others build nests, made of leaves, in the branches. (Working With Wildlife, 2002) To prepare for the winter squirrels collect their food and bury it in various locations. This is known as "scatter hoarding". Because of the means by which they gather food squirrels tend to become very territorial. (Yahner 2001, 60) Their sense of smell is also heightened to aid foraging abilities. As they do not remember the exact location of their buried nuts, squirrels are able to smell nuts even through a pile of snow twelve inches deep. (Whitaker Jr. 1980, 372)
Squirrels typically claim areas one to seven acres in size. Although rural squirrels tend to claim larger areas, they are more protective because they have more natural predators to deal with. On the other hand, Squirrels living in more populated areas have different concerns. They have had to learn to coexist with humans in the past century. As a result, these squirrels have, in a sense, become more domesticated. They tend to eat various foods found in trashcans or provided directly by humans. (The Squirrel Place)
Physical Attributes of Squirrels
Squirrels, who are members of the rodentia order, have a very acute sense of vision, possessing the ability to see color. (G. Jacobs 1981) A squirrel's eyes are located on the sides of its head, resulting in a superior field of vision while lowering its depth perception. (Steele and Koprowski 2001, 7) Squirrels are mammals of medium size, generally weighing between ten and twenty-five ounces. From afar, there are no distinguishable traits between most male and female squirrels. Their bushy tales are a mechanism for balance as well as communication. The coloring of the squirrel serves as a camouflage, making it more difficult for predators to spot. (Steele and Koprowski 2001, 12-13) Squirrels possess another defense mechanism in that they have the ability to turn their feet one hundred and eighty degrees. This pliability of the ankle allows the squirrel to quickly scurry up the nearest tree to escape threats from predators. (Jenkins and McClearn 1984)
Like most small mammals, squirrels have many predators. Large birds, such as hawks, falcons, eagles, and owls are notorious for swooping down and carrying off squirrels. Another predator is the long-tailed weasel. Not only will weasels capture adult squirrels, they will also invade their nests. Weasels can eliminate up to half of squirrel young in one season. Other animals wishing to prey upon squirrels are the coyote, the red fox, and the raccoon. (Small Mammals of North Dakota)
The Squirrel and its Name
Scientifically, the squirrel is known as the Sciurus. The Greek word skia combined with oura means shade tail. (Steele and Koprowski 2001, 13) This can be translated as "he who sits in the shade of his tail." (The Squirrel Place) The squirrel received the nickname "bushy tail" as a derivative of its scientific name. Predators such as these create an instinctive fear within squirrels. As a result, approaching organisms are often viewed as a threat.
In The Impact of Humans on the Domestication of Squirrels, researchers studied how urbanization and humans affect squirrel behavior. (Dann et.al.) They ran test similar to ours in Pfeffer Park and on Main Campus and compared the results. However, instead of comparing the style of approach, they looked at the way in which a safe place of retreat affects the behavior of the squirrel. They found that, on average, squirrels on Main Campus would allow an approaching researcher within 9.2 feet. Squirrels in Pfeffer Park would only allow people to approach 16.9 feet from them. They concluded that although humans do seem to affect the behavior of squirrels, this difference, when analyzed by T-tests showed that was not significant. In addition, they found that a place of safety also made no significant difference.
Specific Research Design:
We designed this experiment to measure the variation between the responsiveness of squirrels toward an approaching human. We will then use this data to compare the reactions of squirrels in a densely inhabited area to those in a less populated area. We plan to approach sixty total squirrels in a variety of styles on two separate areas of campus. The densely inhabited area is located on Main Campus in the quad near Upham Hall. We selected this area because of the consistent number of circulating students along with the even distribution of trees. The less populated area is located on Western Campus, directly to the right of Peabody Hall. We selected this area based on the fact that the environment and tree distribution is similar to that of the quad, however the amount of human inhabitants is minimal.
In this experiment, the independent variables include three specific styles of approach: walking, running, and crawling. The dependent variable is the distance reached before the squirrel flees. All other elements will be controlled. In order to rule out possible clothing distractions, each person will wear a dark shirt and jeans. Gym shoes will also be worn in order to minimize the sound of approaching footsteps. Based on the average distance we are able to approach the two groups of squirrels, we will determine the least-threatening style of approach. In addition, after comparing results we will be able to determine whether human population has an effect on squirrel behavior. Finally, we will run a t-test to see if the differences we found are significant.
Materials and Methods:
As previously mentioned, our group members will have a uniform appearance consisting of a dark shirt, jeans, and gym shoes in order to limit variables. Markers or green cloth and a tape measure will be necessary to measure the approach distance. A data sheet along with a digital camera will be used to accurately document and present our results.
Each group member will be assigned a different style of approach. The group member will approach ten squirrels at each location. All tests will be run in the evening. The group member will target only unmoving squirrels and maintain a constant speed of approach. Foraging squirrels will not be approached for their reaction may be different as it protects its food or territory. Upon approach, the group member will drop a marker as soon as the squirrel flees. The approach distance will be determined by measuring the distance between the marker and the location where the squirrel began to flee.
In order to involve the class in our study, we plan to explain the lab during the first part of class and allow the students to create their own hypothesis. We will then divide the class into groups so that they can experience the squirrel reactions for themselves! (They will only test five squirrels on either main or western campus.) When the data collection is complete, we will reveal our group findings. We will test the to see if the class results are consistent with our findings. Based on their individual results we will ask them to come up with a conclusion regarding their results in comparison with ours.
c) Research Timeline:
September 21- October 1 Our main focus will be compiling information to support our hypothesis and to provide ample information on the habits and behaviors of squirrels.
October 7 Proposals are due..
October 7- October 27 We will run tests and record results.
October 28- December 10 We will analyze data. We will also add any additional information to our report and interpret our results
December 10-17 We will use this time to put any finishing touches on our paper.
December 17 Final paper due!
Birney, Elmer C. and J. Knox Jones, Jr. (1988). Handbook of Mammals of the North-
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Burt, William Henry and Richard Phillip Grossenheider. (1980) Mammals. (3rd. ed.)
New York: Houghton Mifflin Company.
Dann, Jill; Dean, Laura; Dodds, Cleveland; Miller, Heather; Zinn, Lisa; (2002) The
Impact of Humans on the Domestication of Squirrels
Emry R.J., and R. W. Thornington, Jr. (1982). Smithsonian Contribution to Paleobiology.
Jacobs, G.H. (1974) Brain, Behavior, and Evolution. (pgs. 307-321)
Jenkins, F. A., Jr., and D. McClearn. (1984). Mechanisms of Hind Foot Reversal in
Climbing Mammals, Journal of Morphology. (pgs. 197-219)
Lepp, George; Morton, Martin L; Sherma, Paul W. (June/July 1979) Four Months of the
Ground Squirrel, Natural History, Volume 88 Issue 6. (pg. 50)
Orr, Robert T. Mammals of North America. (pg. 58) New York: Doubleday & Company
Steele, Michael A. and John L. Koprowski. (2001). North American Tree Squirrels.
(pg.1, 7, 12-13). Washington: Smithsonian Institution Press.
Whitaker, John O. Jr. (1980). The Audubon Society Field Guide to North American
Mammals. (p. 370, 372). New York: Alfred A. Knopf.
Yahner, Richard H. (2001). Fascinating Mammals. (pg. 60) Pittsburgh: University of
Small Mammals of North Dakota
The Squirrel Place (1995-2004) www.squirrels.org
Method Distance On Main Campus Distance on Western Campus
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