Raccoons: Beach Bandits
Raccoons (Procyon lotor) are small mammals found on Mayne Island and across North America. Similar to what has happened with blacktail deer, raccoon populations have increased following the loss of the large predators that once kept them in check, and that is causing problems for the species they feed on such as birds and other small animals.
Raccoons have had immense success adjusting to urban environments and changes to their natural habitats caused by people. While other species have not been able to adapt as well or as quickly to human landscapes, it has allowed raccoon numbers to increase. Here on the Gulf Islands, humans have driven away large carnivores such as bears, wolves and cougars. These big predators used to feed on raccoons and, as a consequence, raccoons developed behaviours to avoid being eaten.
Now, in the absence of these large carnivores, raccoons are no longer so cautious when they go about their daily business. This behaviour is similar in some large herbivores such as blacktail deer that are also no longer fearful. This lack of predation by carnivores has allowed raccoons and deer to spend more time eating, resulting in more of their food being consumed.
If carnivores were still in the picture, raccoons would likely avoid feeding in open areas or feeding during the day, as these activities would put them in danger. Keeping a watchful eye out for potential sources of danger would cut down on the time spent foraging for and consuming food.
Researchers have been experimenting with playing recordings of predator calls along shorelines, and have observed that this alarmed the raccoons and led them to change their behaviour. They found that intertidal crabs, intertidal fish, polychaete worms, and red rock crab populations all increased when raccoons were frightened off. Researchers concluded that managing raccoons’ excessive foraging could potentially help restore bird and intertidal species populations in the Gulf Islands.
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- Suraci, J. P., Clinchy, M., Dill, L. M., Roberts, D., & Zanette, L. Y. (2016). Fear of large carnivores causes a trophic cascade. Nature Communications, 7(1), 10698-10698. https://doi.org/10.1038/ncomms10698
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