Study Finds Interbreeding and Mutated Pigment Gene Turned Grey Squirrels Black

Posted on August 16, 2019

A melanic, or black, fox squirrel

Researchers have determined that some grey squirrels have black fur because of interbreeding and a faulty pigment gene. Black squirrels are the same species as grey squirrels. The only difference between them is the color of their fur.

The research study was led by Dr Helen McRobie of Anglia Ruskin University (ARU) and was reported in the journal, BMC Evolutionary Biology. The black fur is caused by the grey squirrel having a pigment gene with a missing piece of DNA.

The researchers found that the faulty pigment gene in grey squirrels is identical to a faulty gene found in the fox squirrel, a closely-related species native to North America that also has black variants. Testing DNA from grey and fox squirrels found across the U.S. and British Columbia, Canada, the researchers discovered that other signatures on the mutated gene are more closely related to the fox squirrel. The scientists say this suggests it is highly likely the mutation first arose in the fox squirrel and was then passed to the grey squirrel through interbreeding.

Dr. McRobie, Senior Lecturer in Biomedical Science at Anglia Ruskin University (ARU), says in the announcement, "The fact black grey squirrels have become so common right across North America is possibly because black fur offers a thermal advantage, helping them inhabit regions with extremely cold winters. This may have contributed to the expansion of the grey squirrel's range during the past 11,000 years, following the end of the most recent ice age, helping them spread further north into Canada."



Image: Amanda K Ciurej