Justin Suraci, a PhD student in Ecology at the University of Victoria in British Columbia, Canada, posited the idea that foraging raccoons might be frightened off just by the sound of a natural predator without the predator actually being present. To test their thesis, Suraci and colleagues set up speakers around the area and played recordings of dogs and sea lions barking. As a result, the noticed a significant decrease in foraging time.
The dog sounds cut the raccoons’ foraging time by 66 per cent over the course of a month. They also led to a rise in the abundance of crabs, fish and worms that raccoons feed on in the intertidal areas, and in turn, to a decline in numbers of those animals’ prey and competitors.