Squirrel Abundance in Urban and Woodlot Environments

Introduction     

     This field study was conducted in collaboration with Angela Joseph, Enrique Sapena Ventura, and Hasan Hamam. The topic of squirrel abundance was prompted by a shared curiosity about the friendly nature of squirrels that were observed on campus. After some discussion of the environmental factors that may lead to such behaviour, it was decided to investigate the abundance of squirrels found in heavy traffic areas of the York University campus, in comparison to a more natural habitat in a woodlot environment.

     The remains of food left by humans on the campus, both in garbage cans and on the ground, is believed to play a role in the abundance of squirrels in the urban environment. With more food readily available in the more urban areas of the campus, the squirrels are hypothesized to be more abundant in these areas, as commensalism between the humans and the squirrels should be present. There is no cost to humans, as the garbage being thrown out is waste to us regardless, but the squirrels have a chance of gaining a meal by scavenging the scraps.

          Predictions

     If there is commensalism between humans and squirrels, it should be expected that there will be a higher abundance of squirrels located in close proximity to the busiest areas of the campus. This should result in most of the squirrels being near to the central area of the campus, and a much lower number of squirrels in the woodlot. As there is some risk to the squirrels of being in such close contact with humans (we are fairly large omnivores in comparison), the amount of food present should be enough to outweigh the risks, but also be less than the competition of other squirrels feeding elsewhere. This implies that there may be a threshold where the squirrels will have a large enough amount of food to outweigh the risk of coming into too close of a contact with humans, but far enough away to not get trampled or captured.

          Methods

     Data was collected from pre-determined areas of the York University, Keele campus. Efforts were made to maintain a consistent size in the areas sampled by comparing size on Google Maps. The Urban environment data was collected along a path beginning at the front of Vari Hall and following Campus Walk around the west end of Steacie Building, ending at the north-east side of Farquharson building just before the greenhouses. The woodlot environment datasets were collected from the woodlot directly south of Chimneystack road on the east end of the campus. A staggered path was followed beginning at the center of the south side and leading through the woodlot to the north end, then looping around the west side to observe the separate copse of trees at the very south west corner. Both the woodlot and urban paths were followed for both datasets and were walked for a total of 45 minutes each time. Data was collected on two consecutive Fridays between 2:30 and 5:30. Weather conditions on the first field day were overcast with light rain, and weather was was warm and sunny on the second field day.