In our neighbourhood, here in Windsor, it seems that the different varieties (species?) of squirrel are rather friendly. Fraternization among them has produced all the combinations of colours. Body colour and tail colour differences can look a little humourous. Picture a black-bodied squirrel with red (or grey) tail, and similarly, the other two colours. Often, the greys, or other colours with grey tails, will have thin tails. They don't seem to 'fly' as well as the others, which can easily sail from one tree to the next. The greys often come up short on the leap to the next tree. My dog enjoys chasing them around the yard, trying to get them to run up the trees, just to watch them scramble, and sometimes fall into the next yard. When that happens, she struts back to the house, tail flying like a flag. "See what I did! Idjit squirrel is no match for me". It is another story when the mama blue jay sets her sights on my dog, however. Gracie comes running for shelter. Even my neighbour got driven in the house when mama blue jay was waiting for her eggs to hatch.