Although wolves exhibit wide variation in color, adult size and geographic range, they are considered a single species. The only exception is the Red Wolf of Texas and Louisiana which appears to be a fertile cross breed between wolves and coyotes.
Wolves are very closely related to dogs, anatomically different in subtle shapes of their skulls.
Their color ranges from almost a pure white found in the White or Arctic Wolf, through various grays such as the Timber Wolf, to brown and black. Wolves had very wide geographic ranges, being native to the United States, Mexico, Europe and Russia. Though human history, an ongoing effort has been made to eliminate wolves. This has reduced their natural ranges to rather small or remote areas. They still have naturally stable populations in Canada and Alaska.