Gray Squirrel Home Range Size

An analysis of telemetry data from the University of New England's Biddeford, ME campus

This project contains data from the University of New England's course lead by Dr. Noah Perlut entitled Practicum in Field Ecology: Squirrelology. This course has used radio telemetry since 2010 to collect location data for gray squirrels (Sciurus carolinensis) found on the Biddeford, Maine campus. These data have been collected through the Collector app and placed into ArcGIS Online.

Project Goal: This project is a culmination and analysis of telemetry data collected by the squirrelology class since 2010. Through this analysis, we assessed how home range size and seasonality differed between breeding seasons between individuals. The overall goal was to have the data organized and placed into ArcGIS so that it could be visualized and studied in present and future research.

The map below displays all 3,225 data points that have been collected from 37 individual squirrels. Each different color is an individual squirrel represented by its given collar radio frequency at observed locations.

All squirrel locations

Below is a snapshot of the data in the background

Master sheet of project data

Data Selection: Data for this project was selected from squirrels that had been on the Collector app for more than 30 days with observation occurrences, which provided a consistent set of data for analysis.

Area/Home Range Calculation

First Step: After downloading and organizing, these points were placed into their own individual maps where home range area could be calculated by creating polygons to represent the total area they covered based on observed locations from the telemetry data.

Below is an example of these polygons. There was large variation in area covered by individual squirrels that represented their movements on campus.

008 in blue area = 9.797 ha (147 data points 10/5/18-9/18/19) 326 in green area = 4.47 ha (348 data points 11/29/17-1/29/20) 700 in purple = 14.068 ha (25 data points 4/19/19-3/10/20)

Largest Area: Squirrel 807, 42.27 ha (65 data points 1/31/17-5/1/17)

Smallest Area: Squirrel 886, 0.111 ha (26 data points 1/31/17-3/6/17)

Below is a table displaying all individual areas of each polygon (home range) for each squirrel in hectares. The data showed large variation in total area.

Mean Calculated Area/Home-range Size = 8.91 ha SD=9.78

    *This number did not include all polygons due to data-source accessibility issues

Heat Map: Where are these squirrels found?

Heat Map

This heat map above shows the distribution concentration of the squirrels on campus. The squirrels tend to stick close to the wooded areas of campus, but they certainly use the campus to travel between these areas.

Locations of squirrels on campus from Jan 2017-Mar 2020, 2,135 data points (008 in green for reference)

Breeding vs. Non-Breeding Season

Breeding season occurs from the month of February through the month of September. Non-breeding season occurs from October through January.

This map shows each point as represented by the month it was recorded

Breeding vs. Non-Breeding Seasons

Map showing occurrences during breeding season (orange) and non-breeding season (blue)

Data and maps show little to no variation between location and the given month or season

Chart showing observations per month since 2010

What does this all mean?

The data collected by Dr. Perlut's Squirrelology course provides a great deal of information on gray squirrel home range at the UNE campus. The home range calculations show the large range in size covered by a squirrel. A mean area of 8.91 ha is a huge area for a squirrel to cover especially when faced with the risks of high vehicle and foot traffic found on campus. Being able to visualize their movements on campus provides a great look into how these areas come to be so large. Although breeding season comparisons did not show much variation, it is an important aspect of all wildlife ecology to understand how wildlife uses the land around them to carry out their necessary processes.

This data shows not only the widespread area used on the UNE campus through the representation of the maps, but it also shows the ability of GIS to track and monitor a species through the practice of telemetry. Creating these maps and models allows for a physical representation of the work being done and provides a base for future research to build off of. Being able to use GIS to continue this research will be largely beneficial by providing a place for data to be plugged into these exact maps and allow for continued analysis of the data.

Thank you to Dr. Noah Perlut PhD, Dr. Marcia Moreno-Baez PhD, the squirrelology course, the University of New England Department of Environmental Studies and the University of New England.

All maps created using ESRI products (ArcGIS Pro, ArcMap, ArcGIS Online, Collector), along with Microsoft Excel

Photo Credit (Squirrel Photo): John Ewing, Portland Press Herald

Master sheet of project data

Largest Area: Squirrel 807, 42.27 ha (65 data points 1/31/17-5/1/17)

Smallest Area: Squirrel 886, 0.111 ha (26 data points 1/31/17-3/6/17)

Chart showing observations per month since 2010