Resource Overlap, Interspecific Interactions and the Distribution of the Flying Squirrels, Glaucomys volans and G. sabrinus

Publisher Website
Google Scholar
Abstract
The North American flying squirrels G. volans (Linnaeus) and G. sabrinus (Shaw) provide an opportunity to analyze the role of various factors determining the ranges of 2 marginally sympatric species. A survey of the literature and observations of wild and captive Glaucomys suggest that G. volans is almost always associated with hardwood trees, while G. sabrinus is usually found in conifer forests but may occupy hardwood areas as well. Especially in the North, G. volans appears to depend on tree hollows for nesting sites while G. sabrinus also nests in hollows but frequently uses outside nests. Although omnivorous, G. volans is mainly a seed and nut eater over much of its range and depends on these resourced during the winter. The northern part of its range coincides with the northern range limits of most mast species, especially the hickories (Carya) and oaks (Quercus). G. sabrimus, also relatively omnivorous, often subsists on lichens and fungi. Since lichens are abundant in its habitat and are eaten by few other animals, G. sabrinus has an exclusive energy source. Captive G. volans and G. sabrinus were studied in large outdoor cages and in the laboratory. Individuals of the same species always shared a nest. Individuals of different species showed considerable mutual tolerance but G. volans was able to control nests more often than G. sabrinus. Since tree hollows are a resource for which animals are likely to compete in the wild, nest competition may decrease the extent of sympatry. G. volans was markedly more aggressive than G. sabrinus in defending a home area. In a large cage with spruce (Picea) planted on one side and sweetgum (Liquidambar styraciflua) on the other, wild-caught G. volans showed a marked preference for the hardwood habitat: wild-caught G. sabrinus showed no preference. Native G. volans showed a slight preference for a hardwood habitat. When pairs of both species were placed in the habitat cage, G. volans always occupied the hardwood side. The relationship and distribution of the flying squirrels G. volans and G. sabrinus may be largely attributed to particular resource requirements and interspecific interactions.