Monday, May 14, 2012

A Black Squirrel

My Judy wanted me to share this with you all.  This weekend she traveled to Parkersburg to visit our family.  She stayed with cousins, Sheryl and Marshall Daniels.  Marshall places peanuts on the porch railing to feed the squirrels.  They have a black squirrel that regularly shows up for food.  Judy was excited.  The black squirrel is actually a mutation of the gray squirrel  It is called melanistic.

As a melanistic of the Eastern Gray Squirrel, individual black squirrels can exist wherever grey squirrels live. Grey mating pairs can not produce black offspring. Here is an explanation for my genetics students.  

Grey squirrels have 2 copies of a normal pigment gene and black squirrels have either 1 or 2 copies of a mutant pigment gene. If a black squirrel has 2 copies of the mutant gene it will be jet black. If it has 1 copy of a mutant gene and 1 normal gene it will be brown-black. In areas with high concentrations of black squirrels, mixed litters are common. 

The black subgroup seems to have been dominant throughout North America prior to the arrival of Europeans in the 16th century, since their dark color helped them hide in virgin forests which tended to be very dense and shaded. As time passed, hunting and deforestation led to biological advantages for grey colored individuals. Today, the black subgroup is particularly abundant in the northern part of the Eastern Grey Squirrel's range. This is likely due to the significantly increased cold tolerance of black squirrels which lose less heat than greys.Black squirrels also enjoy concealment advantages in denser northern forests.


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