A recording of wild dogs barking was able to keep wild raccoons from foraging along the shoreline of various islands – which also helped the population rebound among fish and crabs (raccoons’ prey), a new study suggests.
In the new study – published Tuesday (Feb. 23) in the journal Nature Communications – the researchers found that fear can help when it comes to maintaining healthy ecosystems and protecting biodiversity.
Previous studies have found that spiders, which could scare grasshopper prey, led the grasshoppers to alter their foraging behaviours, according to the researchers. Thus, the entire plant community also changed. However, the researchers were not entirely sure whether the same fear-based method would apply for larger animals and at a greater scale.
Justin Suraci, an ecology doctoral candidate at the University of Victoria in Canada, said that scientists were split as to whether the effects of fear would be relevant for predators and prey in real ecosystems. Until now, studies on the cascading effects of fear have been unable to separate the various factor affecting wildlife from the effects of fear, Suraci explained.
A lot of scientists are of opinion that the reintroduction of wolf populations to Yellowstone National Park has helped decrease elk overgrazing – which occurs when plants are exposed to intensive grazing for longer periods of time and with insufficient time to recover. That enabled the plants to grow back, making songbirds and beavers come back to the park, which is located primarily in the state of Wyoming, but also extends into Idaho and Montana.
On the other end of the spectrum, opponents of the reintroduction of wolves have said that other environmental changes were in fact responsible for the revival of Yellowstone National Park’s ecosystem, according to Suraci.
To isolate the effects of terror among larger animals, Suraci and his colleagues analysed the ecosystems on the Gulf Islands, located off the coast of British Columbia, Canada. Wild raccoons that live on the islands usually look for fish that can be found in tidal zone, and red rock crabs live on the shorelines.
According to the researchers, wild raccoons used to be hunted by black bears, wolves, and cougars, but because those predators no longer live on the islands, they are now only hunted by dogs. Even though dogs do not kill that many raccoons, data has shown that chasing and barking at the animals was enough to instil a predator fear, Suraci explained.
The team of researchers played recordings of wild dogs barking along the shoreline. They also played the sounds of stellar sea lions, harbour seals, and other types of seals (pinnipeds). To track the number of raccoons prowling the shoreline, intertidal fish, shore crabs and red rock crabs, the researchers also used cameras over a one month period.
The results showed that by the end of the month, the intertidal fish population increased by 81 percent, the number of shore crabs doubled, and the number of red rock crabs increased by 61 percent, all because fewer raccoons were feeding on them.
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