Gray Squirrels as Subjects in Independent Study
The American history teacher
In the context of field ecology laboratory courses or the expanded popularity of independent study projects in college curricula (Knisley & Conway 1986), it is often necessary to devise laboratory exercises that involve the study of animal behavior. This article describes experiences and insights gained from using a local gray squirrel (Sciurus carolinesis) population in a series of independent study/research projects at the Wilkes-Barre Campus of the Pennsylvania State University. The
... rsity. The abundance and extensive range of the gray squirrel make it an excellent experimental animal. It is often found in locally high densities throughout its range of the eastern United States. Squirrels serve as good experimental subjects because they are free ranging animals located on or near most campuses or parks and have generally acclimated to humans and will proceed with their normal routine in the presence of an observer. Another important consideration when using a species such as the gray squirrel in laboratory exercises is the fact that all students will be instantly familiar with the animal and its habitat. This familiarity eliminates the need for extensive introductory lectures. For an excellent summary of the basic biology of the gray squirrel, see Mammals of Pennsylvania (Doutt, et al. 1977). The key to success of any project in experimental animal behavior is helping students focus on a particular problem and formulate appropriate questions or hypotheses to explore. By providing them with some possible avenues of investigation (see suggestions below), it is possible to get the students thinking about a particular project. This is best accomplished by small group or individual discussion with the student researcher or research team. In order to facilitate discussion and to help students focus on testable hypotheses, I find it helpful to ask questions such as: What are the typical behaviors you might expect to observe in a squirrel? Why do squirrels hoard or cache nuts? What types of decisions regarding food hoarding, food consumption and predator avoidance might a squirrel to make? What impact might these different decisions have on the ability of a squirrel to survive in the short-term or long-term? Although it is unlikely students will be able to design an experiment and collect sufficient data to fully answer these questions, the discussion and thought provoked by posing them is often interesting and useful. Intensifying the Interactions It is possible to observe many behaviors of the gray squirrel without any manipulation of the population. However, such observation will be limited to feeding behavior and occasional interactions among individuals in the feeding groups. To increase the efficiency of observations or if repeated observations of individuals are needed, it may become necessary to intensify interactions among individuals. The intensifying of the interactions may be accomplished easily and inexpensively by the construction of a feeder for dispensing corn or other food items. The feeder design I have found successful is constructed of wood scraps and coffee cans and incorporates a small feeding platform allowing only one animal to feed at a time. By restricting access to the food supply, one is increasing the likelihood of confrontation during feeding periods. Use of a feeder as described provides the opportunity to observe the social hierarchy or "pecking order" of individuals within the group that visits the feeder. The displays and vocalizations of squirrels at the feeder during these periods of interaction are interesting observations for many students and provide numerous examples of how animals communicate (Taylor 1966). Additional interactions are likely to take place on the ground below the feeder because, as squirrels visit the feeder, sufficient food to at-tract other animals will be dropped to the ground. During observation periods, my students have reported interactions among gray squirrels, gray and red squirrels (Tamiasciurus hudsonicus), gray squirrels and chipmunks (Tamias striatus), and among gray squirrels and several bird species at the base of the feeder. Although we have not systematically investigated these examples of between-species communication, they are often intense and always interesting. Although it is obviously not essential to construct a feeder since squirrels can be attracted to an observation point by simply dispensing food on the ground, I have found the use of a feeder is beneficial because it focuses the point of interaction among individual squirrels and consequently makes observation easier. Marking the Animals In the context of many experiments it is not essential that individual animals be marked. A number of interesting behavioral observations are possible without positively identifying or distinguishing among individuals of a group, and many instructors may choose, at least initially, to start with such observations in their classes. If food is consistently provided at the same location, it has been my experience that the same individuals return repeatedly to that location. Other investigators (Lima & Valone 1986) also suggest that the composition of feeding groups at feeding stations does not change radically over periods of six to eight weeks. Therefore, if one provides food for a period prior to the onset of the project to initially attract squirrels to an area and then continues to provide adequate food during the experiment, one can assume that the same animals will re-Carl R.