Social behavior:

Although a red fox is normally a solitary animal, it won't completely isolate itself from other foxes. Red foxes do not hunt in packs like wolves do, but will form a pair (a mated male and female) that can last for life. This pair will travel, hunt, and feed on their own, but will occasionally meet to play or groom each other.

In more urban areas, it is common for other foxes to join the dominant, mated pair. These additions, usually known as "helpers", are generally the offspring of the dominant pair who remained with their parents for certain reasons, such as the difficulty of them having difficulty finding and establishing their own territory.

Territorial behavior:

Foxes are known to be territorial animals because they will establish and defend an area where they live (a "territory") against other foxes.

Red foxes will use "scent marking" (using urine, feces, or their own scent from the multiple scent glands on their body, such as on their tail, face, or feet) to communicate with other foxes and let them know where the borders of their territory are situated. If foxes do happen to meet each other in a marked off territory, it is unusual for fights to occur. Red foxes will usually only attack strangers instead of neighboring foxes.

If a fox leaves its territory for a period of time, another fox is likely to move in and establish its own territory in that area. 

Reproduction and development:

The red fox typically mates from January to March. Right after mating, the female will create a den in which she will give birth and care for the kits. About two months after mating, the female will give birth to a litter of 1-12 babies, or "kits". The male is in charge of bringing food to the female while she is caring for the kits in the den. The kits will begin to venture out of then den in order to play and learn about their surrounding environment when they are about a month old. By the time the kits begin exploring outside of the den, the mother will begin to feed them regurgitated food and bring them live prey so they can begin practicing their hunting skills. A kit will leave the care of its mother and the birthing den once it is about seven months old.

Denning behavior:

Dens are mainly used just as "birthing dens" and most foxes will choose to sleep out in the open and use their tails to cover their noses in order to stay warm. However, when a red fox does use a den, it will usually just enlarge an existing rabbit or marmot den instead of going through the trouble of making its own.

Foxes living in more urban areas have been known to make dens in unused buildings, garden sheds, or in crawlspaces under porches.

Notable Defense Mechanisms:

The red fox utilizes multiple defense mechanisms such as their sharp teeth, musky odor (which is comparable to a skunk's), small size (which allows it to hide or flee from larger predators), speed, and intelligence.

Red Fox