Southern Squirrels Moving North

OBSERVATION: This observation was originally made by Dr. Jeff Bowman, a population ecologist from the Ministry of Natural Resources and Forestry, and Dr. Paul Wilson, a wildlife geneticist from Trent University.

Historically, the southern flying squirrel (Glaucomys Volans) has occupied most of the Eastern United States – ranging from Florida up to the north shore of Lake Erie. Since 2002, however, these researchers have witnessed great variability at the range boundary of the southern flying Squirrel, with multiple observations of rapid and dramatic population expansion and contraction. During the very cold winter of 2004 in particular, the southern flying squirrel population crashed and their range contracted by greater than 200 km in just one winter. Whereas recently, following a succession of unusually warm winters, the southern flying squirrel expanded its territory northward into central Ontario, even as far north of Algonquin Park. These expansions and contractions have occurring sporadically over the past 14 years with the net result being a gradual range expansion of the southern flying squirrel (See Figure 1). This has created a zone of habitat overlap with the indigenous northern flying squirrel (Glaucomys sabrinus) (See Figure 2). The northern flying squirrel is much larger than its American cousin – with the average adult male weighing in at roughly 90 grams (See Figure 3), compared to the southern’s 65 grams (see Figure 4). The two can be easily distinguished by their belly fur; with the northern having two-tone belly fur that is white at the tips and grey at the base, whereas the southern’s belly fur is strictly white. Dr. Bowman and Dr. Wilson are now evaluating whether there is direct competition between the two species in this zone of habitat overlap. Both species are active over the winter - as they do not hibernate; and both seek out tree cavities to make their nests in. Even with its smaller size, it appears that the southern flying squirrel is more aggressive than the northern. Therefore, if tree cavity numbers become a limiting factor – the southern may have an advantage if competition occurs for these nesting places. The research they are conducting as part of the Flying Squirrel Project also involves documenting the hybridization of these two species in this zone of habitat overlap – where roughly 4% are now cross-breeding. The major ecosystem role of these squirrels is as seed dispersers. Dr. Bowman and Dr. Wilson are investigating if this habitat change, and subsequent hybridization phenomenon, is a positive reaction/adaptation to climate change – or if it will be detrimental to both squirrel species and the environment.

Consultations: Dr. Jeff Bowman

Additional Resources: https://flyingsquirrelproject.wordpress.com