This post may contain affiliate links. As an Amazon Associate, we earn from qualifying purchases.
The red squirrel (Sciurus vulgaris) is a species of tree squirrel typical throughout Europe and Asia. The red squirrel is an arboreal, mainly herbivorous rodent.
In the British Isles, the species’ specimens have declined drastically in recent years. This decrease is associated with the introduction by humans of the grey squirrel (Sciurus carolinensis) from North America.
Red SquirrelGray Squirrel
Grey squirrels (Sciurus carolinensis) native to North America were first introduced into England in 1876. They were distributed to the rest of Great Britain through a rapidly growing population by the early to mid-20th century, taking benefit of food sources, habitats, and lack of predators for grey squirrels. This has led to a decrease in the population of red squirrels (Sciurus vulgaris).
The first documented introduction of grey squirrels in continental Europe was in 1948, and they were brought to Stupinigi (Italy), where there is still a rising population.
Nearly 80% of known grey squirrel introductions worldwide resulted in successful naturalization in the new territory.
The efficiency of the spread of grey squirrels can be defined by the “enemy release hypothesis” when the invading species has better survival because its natural predators are absent.
Grey and red squirrels contest for resources, and greys will pilfer food caches of red squirrels.
In addition to competition for resources, the spread of the squirrel pox virus from grey squirrels to reds is thought to be a significant factor in the decrease in red squirrel populations. Today, the Italian population of Grey Squirrels doesn’t have squirrel pox, so they’re substantially less harmful to Red squirrels.
