The Effect of Approaching Humans on Squirrel Behavior

This topic submitted by Jessca Slack and Martin Yip ( P3Jessca5@aol.com ) on 10/24/04 .

Natural Systems 1 Syllabus---Western Program---Miami University

Abstract:
Here at Miami University, squirrels are all around us. Most of the time they run away quickly when a person walks near them. It may be observable that squirrels not in possession of food will be more approachable. Therefore, squirrels with food will be more inclined to run when approached. This may be a product of, even though the squirrel is concentrated on the food it possesses, their other senses, such as hearing becoming heightened. Additionally, we observe that squirrels in close proximity to a tree while eating will allow humans closer to them. They reason may be that they are more familiar with their surrounding, thus, feeling safer.

Introduction:
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 goal is to evaluate whether a significant difference in approachability exists between the squirrels foraging for and eating food and how close they are to a tree. We hope to answer the following questions: Will squirrels who possess food allow a person to come closer than a squirrel without food? Does the location of a tree, have any effect on the squirrels perception of the approaching human? This is important because 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 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).

Hypothesis:
Our hypothesis is that the squirrels who are not in possession of food will generally be more approachable, possibly letting people approach within three feet. The squirrels with food will be more inclined to flee when a researcher is within four to six feet of it. This belief is due to the observation that while squirrels are eating food, this becomes their focus point, they are not as visually aware of outside activities, yet their other senses become heightened.

Alternate Hypothesis:
An alternate hypothesis is that squirrels in close proximity to a tree while eating will allow a human closer to them. This is because the squirrel is much more perceptually aware of its surroundings. It knows where the tree is and therefore it feels safer allowing humans to continue in their approach because the squirrel has ample time to escape into the tree.

Background Information:
Because the squirrel's size allows them to be seen easily and their habitats are readily observable, squirrels are excellent test subjects. In addition to this, they follow a daily cycle that coincides with our own human cycle (Sherma and Morton 1979, 50). Squirrels are a large group, with many types of appearances and differing habits (Whitaker Jr. 1980, 370). As 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 another. (Orr 58)

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.

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). Migration was an adaptive response in gray squirrels which prevented the overcrowding of suitable habitats during the winter months food shortages. 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 trash cans 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 them (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)

Predators:
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).

Related Studies:
In The Impact of Humans on the Domestication of Squirrels, researchers studied how urbanization and humans affect squirrel behavior (Dann et.al.). They ran tests in Pfeffer Park and on Main Campus and compared the results. However, instead of comparing the squirrel's possession of food, they concentrated solely on 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 possessing food as to those with no food. We plan to approach sixty total squirrels on our selected test location, the area located on Main Campus in the quad near Upham Hall and King Library. We selected this area because of the large amount of squirrels and the availability of food for squirrels. We chose this also to ensure that we were testing as many different squirrels as possible.
In this experiment, the independent variable is the squirrel's possession of food. In our alternate hypothesis, the independent variable then becomes the distance of a tree in relation to the location of the squirrel. The dependent variable is the distance reached before the squirrel flees. All other elements will be controlled to the best of our ability. 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. 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:
Materials:
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. Indicators of 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.

Methods:
Each group member will be assigned a specific role in the experiment. All tests will be run in the evening around the five o'clock hour. The group member will target squirrels with and without food and maintain a constant speed of approach. It will be noted how close a tree is to the squirrel at the time of approach. Upon approach, the chosen group member will drop a marker as soon as the squirrel flees. The other member who is in charge of measuring will walk directly to the spot where the squirrel first moved. The other member will come to pull the tape measurer back to the spot where the maker was dropped. The approach distance will be determined by measuring the distance between the marker and the location where the squirrel began to flee.

Our Day
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! 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.

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!

References Cited:
Birney, Elmer C. and J. Knox Jones, Jr. (1988). Handbook of Mammals of the North-Central States. (p.166) Minneapolis: University of Minnesota Press.

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. (pgs.1-35)
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 Inc.
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 Pittsburgh Press.

Web References:
Small Mammals of North Dakota
The Squirrel Place (1995-2004)

Previous Article
Return to the Topic Menu