black squirrels

Brian Smith-White smithwhi at
Tue Jan 3 22:52:00 EST 1995

In Article <3JAN199509522405 at> "mathog at (David Mathog)" says:
> Each Christmas we travel to my wife's parents' house in San Jose, CA. 
> There are a lot of old trees in that neighborhood, and many many squirrels.
> I vaguely recall my in-laws mentioning several years ago that there was a
> black squirrel about, two years ago I saw one, and this year they appeared
> to make up about half of the squirrel population.  The "normal" squirrels
> are grey, but the black ones are a very dark coal-black color.  In
> addition, and this is based on just watching them - no measurements, the
> black ones are slightly smaller, and their tails are slightly less bushy. 
> Do any zoologists out there know if this coat color allele is common in
> squirrels?  I've never seen a black one anywhere else, but judging from
> their increasing abundance, it looks like it provides a selective advantage
> in that suburban niche. 
> Regards,
> David Mathog
> mathog at
> Manager, sequence analysis facility, biology division, Caltech 
I do not know about the genetic basis for the black coat, however I can 
provide some anecdotal information. In Michigan, black squirrels are found
with a reasonable frequency in the not-suburban areas. There does not seem 
to be an increasing frequency in suburban areas. The black squirrels have
been present at approximately the same frequency for at least one or two
decades according to my wife. (I am a recent immigrant.) The relationship
between the southern California black squirrel and the Michigan black 
squirrel is unknown to me.
As for the selective advantage, what is the relationship between the coat 
color and the color of burnt neighborhoods? Might be similar to the classic
example of moths in England during the early Industrial Age.
Regards,    Brian Smith-White

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