How Did The Eastern Grey Squirrel Come To Europe

How Did the Eastern Grey Squirrel Come to Europe? how did the eastern grey squirrel come to europe

The introduction of the eastern gray squirrel is well documented, and the extent of its spread is closely linked to the size of the population in which it first appeared. A deliberate introduction of grey squirrels to Italy in 1948 was attributed to a diplomat. After World War Two, Giuseppe Casimiro Simonis Vallario took a shine to grey squirrels in Washington DC. He returned with four squirrels and released them near his Turin villa.


The gray squirrel is a threat to European trees. Its habitats are similar to those of the red squirrel, but it is an invasive species and can cause problems in its native environment. The red squirrel is considered the most common and widespread species in Europe, and grey squirrels are the primary culprit in red squirrel extinction. In recent years, however, the grey squirrel has been displaced from some parts of Europe by red squirrels.

The spreading of gray squirrels in the European continent is not a simple diffusion or wave process. Instead, invasions often radiate from multiple foci, including a single native range introduction and long-distance jumps of dispersal that are often human-mediated. The size of the foci, their spreading capacity, and the dates of founding vary significantly from one another. In small populations, stochastic events are more likely to occur.

Food preferences

The Eastern grey squirrel is a very adaptable animal, and its diet is highly diverse. In urban areas, this species often eats bird food, peanuts, and other leftovers from humans. Their diets contain high amounts of phosphate, which inhibits the absorption of calcium in the gut, a problem that can lead to metabolic bone disease and osteodystrophy. In contrast, they eat a variety of nuts, such as acorns, acorn berries, and tree bark.

The Eastern gray squirrel lives in mixed and deciduous forests, but they are also common in urban and suburban areas. Their preferred habitats are tall, dense, and sheltered trees with dense canopies. They use tree cavities and leaf nests for their breeding and feeding habits. Most litters are born in tree cavities or leaf nests, though some observers speculate that the reliance on tree cavities is higher in colder climates.

Genetic diversity

The coat color of the eastern grey squirrel varies geographically and regionally, with brown/gray fur on top and white fur below. This coloration is considered wild. The squirrel’s coat color is derived from its production of melanin, which is found in two varieties. The different mixtures of these two pigments produce different hues. The bands in the fur result from alternate use of these pigments.

In the study, the researchers employed an ADMIXTURE phylogenetic tree to estimate the proportions of learned ancestries in the remaining 99 squirrels. The lowest cross-validation error was observed at K = 3 and individuals were divided into the three geographic regions of Colorado (CO), Illinois (IL), and Wisconsin (WI). In the case of CO vs. WI, the pairwise genetic distance was 0.48 and 0.31, respectively, indicating that the individuals exhibited moderate to strong genetic drift.

Displacement of native red squirrels

The main cause of the displacement of native red squirrels by eastern grays is the competition for food resources, which results in reduced fitness levels in the red squirrel. Eastern greys are larger than red squirrels and have a higher metabolic rate, making them better suited to compete for a greater share of available food. Despite the benefits that Eastern greys offer to local ecosystems, their rapid expansion may be contributing to the extinction of the red squirrel.

The spread of the gray squirrel has been studied by several researchers. Dr Lisa Signorile, an evolutionary biologist at the Zoological Society of London and Imperial College, compiled a genetic database from nearly 2,000 grey squirrels in the UK and Italy. Her research suggests that the two populations of grey squirrels are still genetically distinct and can be used to trace the expansion of new populations. She found that a number of different genetic markers can differentiate the two species and that some are similar but others are completely different.

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