Healthy ecosystems require a full suite of species distributed across a hierarchy of levels on the food chain. If a link is removed, changes in the numbers and types of species will follow.
‘Mesopredator release’ is a phenomenon that occurs when top predators are removed from ecosystems. It allows smaller, mid-level predators to increase in numbers and consume prey at higher rates. This can lead to extreme reductions or even extinctions of species at lower levels on the food chain.
BC’s Gulf Islands Archipelago is an excellent place to study ‘mesopredator release’. As a PhD student at the University of Victoria working with Raincoast, I am examining how the loss of wolves, cougars and bears has allowed smaller invasive predators, specifically raccoons, to flourish. When raccoons arrive on islands where they are not native, considerable changes can occur to songbird populations and intertidal animals. By comparing islands with and without raccoons, we hope to understand the effect that unnaturally high raccoon numbers have on local biodiversity, a result that should translate to other places where wolves, cougars and bears have disappeared.
A lack of top predators doesn’t just affect raccoon numbers. Research suggests that fear of predators alone can change an animal’s behaviour. With no fear, each animal does more of what it likes; namely eat and breed. Understanding how raccoons behave with and without large carnivores present is key to understanding the effects of predator loss.
Ideally, the raccoon mesopredator project will inform conservation and park management in the southern Gulf Islands. I am extremely excited to be joining the Raincoast team and look forward to the opportunity to help protect BC’s rich biological heritage.
by Justin Suraci, biologist and UVic PhD student
PS – Raincoast has a leveraged external funding for most of this project. Our part is only $6,000 which we need to secure by the end of August. Your support will help us meet our fundraising goal.
Or mesopredator release? A new study examines the impact of unnaturally high numbers of raccoons in Canada’s Gulf Islands.
AN UNBALANCED DIET As Gulf Islanders know, the lack of predators has also allowed deer numbers to explode, dramatically impacting native plant life. These imbalances underscore the importance of wolves, bears and cougars to ecosystem health.
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