Answer
Red squirrels in Ontario are victims to many predators, including hunting birds and coyotes. They are even victims to their own species, as male red squirrels will kill their pups in acts of infanticide. Grey squirrels, however, are the number one species that endanger red squirrels.
Grey squirrels, the more sociable cousins of red squirrels, compete for the same food sources as red squirrels. The red squirrels, who prefer to be alone, have a harder time scavenging for food. However, hunger is not the only problem that kills red squirrels.
Grey squirrels carry a virus called squirrel parapox virus. This virus, which does not affect grey squirrels, are transferred to red squirrels through infected lesions and contaminated crusts. It causes skin ulcers, lesions, and scabs along with lethargy.
Death, which normally follows after being affected by the virus, is a long and drawn-out process for the red squirrels. It is estimated that red squirrels die at a rate of 20 to 25 times faster in virus-infected areas than areas without viruses.
Grey squirrels have also been so problematic to red squirrels that Ireland’s red squirrel population is even going extinct. In Canada, red squirrel populations are currently under control, although wildlife organizations are aware that grey squirrels can dwindle red squirrel numbers very fast.