Eastern Gray Squirrels

The introduction of the Eastern Gray Squirrel to the western US is a perfect example of why exotic animals should not be released into the wild. Most people now probably think that the common suburban gray squirrel with the bushy tail that scurries all over our back yards is native to the west.
In fact the eastern gray squirrel was brought to the west coast by the early 1900’s and has become the most common squirrel in many parts of the western US. It has also been introduced to many parts of Europe, and there is concern that it may completely replace native species in those areas.
This species is very adaptable, and is a prolific breeder. Typically there are two litters of young annually, with 2-6 young per litter, although as many as 8 in a litter have been described. Feeding of birds, and purposely or incidental feeding of the squirrels, has led to proliferation of the species in many suburban neighborhoods. These animals do fall prey to hawks, skunks, domestic and feral cats, and humans, but have clearly been able to thrive in most areas to which they have been introduced.
Although these Eastern Gray Squirrels are one of the most prominent, and both loved and hated, of introduced species, many other species are likely more harmful. Many plant species are incredibly invasive. Released pet bull frogs are threatening to overwhelm many amphibian and other species competing for food and habitat. European Starlings and English House Sparrows are cavity nesters, and had nearly brought native US bluebirds to become endangered until ingenious birders discovered the secret of bluebird trails and boxes.
The take-home message is don’t think you are being kind by releasing pet exotic animals to nature. They may thrive all too well, putting unnatural selective pressure on native plants and animals.

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