Squirrels in the Greater Vancouver Regional District (GVRD)
Emily Gonzales, MSc.
Richmond has three squirrels, Douglas squirrels (Tamiasciurus douglasii), Northern Flying squirrels (Glaucomys sabrinicus) and the introduced Eastern Grey squirrel (Sciurus carolinensis). Douglas squirrels are small, energetic, diurnal squirrels. They can be identified by their brown bodies with rusty bellies. Very territorial, you may have heard a Douglas squirrel chatter at you as you walk Richmond Nature Park’s trails. Flying squirrels are rarely seen due to their nocturnal nature. They are small squirrels with large eyes and a flat tail that they use to steer as they glide between the trees.
The most commonly seen urban squirrels are Eastern Grey squirrels. Eastern Grey squirrels can survive in a variety of habitats and are generalist foragers. This has likely assisted their successful establishment in many areas where they have been introduced. The squirrels are native to the Eastern United States and Canada. They have been introduced to Vancouver, Victoria, Calgary, and Seattle city parks in western North America. Other introductions have occurred in Italy, Scotland, South Africa, England, and Ireland (Lloyd 1983). The introductions have caused concern in Europe where they are believed to be displacing the native European Red squirrel (Sciurus vulgaris) (Lloyd 1983; Gurnell and Lurz 1997). However, there is no conclusive explanation for the displacement. In the five years that I have been studying squirrels, I could not find anything but anecdotal evidence that Eastern Grey squirrels are displacing native squirrels in BC. All three species have coexisted in Stanley Park for over 90 years. Distribution data throughout the GVRD shows that native and non-native squirrels coexist in municipalities where native squirrels have their preferred habitat and sufficient resources.
Six or eight squirrels of mixed morphology, black and grey, were introduced to Stanley Park in Vancouver, BC, in 1909 (Steele 1985). By the 1950’s, the population was suspected to be at maximum carrying capacity and “…effectively prevented from spreading from [Stanley] park by sea on three sides and by a densely populated city on the fourth” (Robinson and McTaggart-Cowan, 1954). Although individual squirrels were sighted outside the park boundaries, it was not until the 1970’s that viable populations were observed beyond Stanley Park. Presently, Eastern Grey squirrels are found throughout the GVRD and continue to increase in population density. Figure 1 shows the relative number of Douglas squirrels and Eastern Grey squirrels brought to wildlife rehabilitation shelters throughout Greater Vancouver. Figure 2 shows some of the Eastern Grey squirrel sightings in the GVRD showing the southeast dispersal emphasis. Eastern Grey squirrels have been unable to spread as quickly through the dense coniferous forests and mountains in the north and ocean to the west.
Figure 1: Number of Douglas and Eastern Grey squirrels admitted to GVRD wildlife shelters. There has been a general increase in Eastern Grey squirrels since 1987.
Figure 2: Eastern Grey squirrel dispersal in the GVRD showing the southeast dispersal preference.
ReferencesBarkalow, F.S. and Shorten, M., (1973) The World of the Gray Squirrel.
Barkalow, F.S., Hamilton, R.B., and Soots, R.F. Jr. The vital statistics of an unexploited gray squirrel population. Journal of Wildlife Management, 34(3): 489-500.
Gurnell, J. & Lurz, P.W.W. (eds.) (1997) The conservation of red squirrels Sciurus vulgaris L. PTES, London 163pp.
Hall, E. Raymond (1981), The Mammals of North America. 2nd ed. New York, Wiley.
Lloyd, H. G. 1983. Past and present distribution of Red and Grey squirrels. Mammal Review 13, 69-80.
McTaggart-Cowan, I. and Guiguet, C. J. (1973) The Mammals of British Columbia. 5th ed. Victoria, British Columbia Provincial Museum.
Merilees, W. (1985) How far has the Grey squirrel spread? Discovery 13 (4): 124.
Merilees, W. (1986) Eastern Grey squirrels around Greater Vancouver. Discovery 15 (1): 17-19.
Merilees, W. (1992) Yellow-belled marmot and Eastern Grey squirrel update Greater Vancouver area. Discovery 21 (3): 111-112.
Riege, D.A. (1991) Habitat specialization and social factors in distribution of red and gray squirrels. Journal of Mammalogy 72(1): 152-162.
Robinson, D.J. and McTaggart-Cowan, I. (1954) An introduced population of the gray squirrel (Sciurus carolinensis gmelin) in British Columbia. Canadian Journal of Zoology 32: 261-282.
Steele, R.M. (1985) The Stanley Park Explorer. Vancouver. Heritage House.
Emily completed her Masters at the University of Guelph in December 2000 where she examined competition between non-native Eastern Grey squirrels and native Douglas squirrels and modeled the spread of the introduced Eastern Grey squirrel using GIS in BC. She will be examining conservation area design in BC for her PhD with a goal of determining “how to build a better park” by incorporating the multiple facets that go into reserve design. You can contact her at email@example.com