The gray fox, Urocyon cinereoargenteus, is a small nocturnal omnivore native to North and South America. They range from southern Canada, through most of the United States, and throughout Mexico and the other Central American nations, all the way to northern Venezuela and Colombia.
The gray fox is one of only two members of the genus Urocyon, the other being the critically endangered Island fox of the California Channel Islands, which is believed to be a direct descendant of the gray fox. Urocyon is considered to be the most primitive of existing canid genera, and indeed, gray foxes show some traits not shared with other foxes. Most notably, they are the most arboreal of all canids. Only the gray fox, and the Asian Raccoon dog can climb trees to any notable extent at all, but between the two, the gray fox spends far more time in the trees.
Physically, the gray fox looks fairly similar to the red, other than coloration. They're silvery-gray over most of the body, with a black and gray tail, and rusty or buff-colored patches on the legs and face. Most, but not all, have white fur on their neck and cheeks. They're fairly small, about a meter long, and anywhere from four to eight kilograms in weight, making them about the size of a large domestic cat.
Like most foxes, they're omnivores. Most foxes, though, mostly eat meat, supplemented with some fruit and other vegetable matter. The gray fox, on the other hand, is more strongly herbivorous than its kin, like the red fox or the kit fox. They do take quite a lot of live prey, however, mostly rabbits, squirrels, mice, birds and woodchucks. Once in a while they'll take on larger prey, or steal kills from bobcats or lynx. Few animals prey on them, though cougars and jaguars occasionally attack foxes that encroach on their hunting grounds. They compete with red foxes, coyotes and bobcats over much of their range, and with other small canids and felids like the kit fox, red wolf, Canadian lynx and jaguarundi in some regions. Due to their relative lack of specificity in diet, they manage to coexist fairly well with most would-be competition.
The gray fox is locally threatened in some regions, but their population is fairly secure overall. Major threats to them are urban development and trapping. While gray fox pelts aren't in as high a demand as reds, there is still a market for them. They are usually more elusive than red foxes, tending to avoid human habitation where possible. Their tendency to take to the trees also makes them less likely to be seen, even in areas of high population density. I once spent about ten minutes sitting against an old oak before I realized there was a fox looking down at me from the upper branches!
There are few similar species within their range, however. No gray foxes are present on the Channel Islands, where the most similar-looking species exists. In the southwestern USA, the somewhat similar kit fox is fairly common. If you see something that looks like a gray fox scrounging around a garbage dump in a city, it's probably a kit fox - the gray usually avoids cities. The red fox shares most of the gray's range, but most of its color morphs are pretty distinctive. In the extreme north, the arctic fox is found, but it is also difficult to confuse with any other species.