Black squirrels are not a new species, they’re just a common melanistic color phase of the eastern gray squirrel (Sciurus carolinensis).
“Melanistic” comes from the Greek word for black, melanos, and is caused by melanin, the brown or black pigment that gives hair, skin and eyes a dark color. Melanin can be inherited for a permanent dark color as in this squirrel, or it can be produced in greater quantities during tanning or in some diseases.
Melanism can confer a biological advantage when it provides better camouflage. There’s even an effect called “industrial melanism” in which the majority of a species living in a dirty, industrial zone are darker than those who live in a cleaner environment. This was famously documented among peppered moths in Britian during the sooty, late-1800s.
Who knows why Pittsburgh has black squirrels (we haven’t been sooty for half a century) but if you want to see them come on over to the area of Schenley Park that borders — you guessed it — Squirrel Hill.
(photo by D. Gordon E. Roberston from Wikimedia Commons. Click on the photo to see the original)