1. March 22, 2014 at 1:23 pm | permalink

    We have black squirrels, grey squirrels, and fox squirrels in our back yard, as well as red squirrels.

    My reading indicates that black squirrels are a variant of grey squirrels – perhaps the naturalists among us can clarify. They have been moving into our neighborhood over the last 5 years, approximately.

    My squirrel UN seem to co-exist fairly well except when a choice food source is at issue.

  2. By rex
    March 23, 2014 at 12:35 pm | permalink

    coming soon: dark grey squirrels.

  3. March 24, 2014 at 8:36 am | permalink

    @1: black squirrels are indeed a variant of grey squirrel (Sciurus carolinensis). The frequency of the melanistic form is higher in some regions than others. I’m not sure under what circumstances the black coat confers a selection advantage.

  4. By George Hammond
    March 25, 2014 at 1:33 pm | permalink

    The black coloring is due to a variant gene in the system that controls how much pigment gets put into growing hairs. One study found that black gray squirrels lost less heat and had lower metabolism in cold conditions than normal gray squirrels, so the black fur trait may be an advantage in the northern part of the species range (it occurs from Canada to the Gulf Coast). The dark coloration is probably a disadvantage with respect to predators: the black squirrels are easier to spot, especially in winter. So we might see more black squirrels in the north than in the south, and in cities (with fewer predators) than in rural wooded areas.

    The melanistic variant seems to be much rarer in the other two species in town, the small, feisty, American red squirrel (Tamiasciurus hudsonicus), and the largest and most common squirrel in town, the Eastern fox squirrel (Sciurus niger). By the way, the scientific name Sciurus niger means “black squirrel” in Latin, which is an accident of history. The first formal description of the species (by Linnaeus, aka Carl von Linné, in 1758), was apparently made on one or a few black specimens. Linnaeus lived and worked in Sweden and didn’t collect North American animals himself, they were sent to him by others. He didn’t know that the animal he was using as the “type specimen” was an unusual variant.

  5. March 25, 2014 at 2:44 pm | permalink

    I first saw black squirrels in Ontario over 20 years ago and had never seen them here until about 5 years ago. There was a colony on the north side of Sunset and they are now apparently becoming established on the south side as well. I love looking at them but I still love our rambunctious fox squirrels best. They pay their rent with their antics.