On Vancouver Island, A Squirrely Clash of Clans

The Eastern Grey Squirrel is one of the top 100 most invasive species, and on Vancouver Island it is clear how they earned that status.

A squirrel is just a squirrel, right? Wrong.

On Vancouver Island, British Columbia, the invasive Eastern Grey Squirrel (Sciurus carolinensis) is becoming a problem. Grey Squirrels are among the 100 most damaging invasive species in the world according to the International Union for the Conservation of Nature. In Canada this is quite evident.

The invasive Grey Squirrel locally threatens the survival of the smaller native European Red Squirrel (Sciurus vulgaris) and a variety of other native animals. These invaders out-compete native species and introduce viruses such as Parapoxvirus which causes “squirrelpox” in native populations. Grey Squirrels are approximately twice the size of Red Squirrels. The combination of their size and aggressive eating habits makes them adaptable to new habitats and makes it easy for them to out-compete native species for food and habitat. Adaptability might be convenient for the invasive Grey Squirrel, but it is dangerous for native wildlife on the island.

island conservation native european red squirrel
Native European Red Squirrels are threatened by Invasive Eastern Grey Squirrels. Credit: Walter.corno

Squirrels are also responsible for the decline of native birds due to predation of eggs and hatchlings. Gail Wallin the Executive Director of the Invasive Species Council of British Columbia commented:

This is actually a fairly aggressive squirrel. Its population can grow and it will displace the native squirrel population, so it’s a concern in a lot of areas.

Grey Squirrels also threaten Garry Oak ecosystems on Vancouver Island. Garry Oak Trees are the only native oaks in Western Canada and host a world of biodiversity. Squirrels present a problem for the ecosystem by eating just about anything they come across. Karl Larsen, a professor of Wildlife Ecology & Management at Thompson Rivers University explained:

They’re a little omnivore, so they eat just about anything…They can have an impact on plant communities for sure, but they can also impact bird communities because they eat nestlings and eggs.

island conservation squirrels threaten garry oak ecosystem
Garry Oak ecosystems are rich in biodiversity, but on Vancouver Island squirrels are altering the habitat. Credit: Lotus Johnson

Squirrels are often relocated both intentionally and unintentionally but because of the Grey Squirrels adaptability it poses a problem for the native ecosystems. So, make sure not to feed the squirrels, because some squirrels are not just squirrels—they are also invasive species.

Featured photo: European Red Squirrel. Credit: Walter
Sources:
Parksville Qualicum Beach News
Invasive Species Council of British Columbia
Garry Oak Ecosystem Recovery Team

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