Fox dens, also known as earths or burrows, are underground structures that provide shelter and security for these adaptable mammals. These hidden retreats are primarily used as safe havens for raising young, offering protection from the elements and potential threats. While many people associate foxes with dens, these structures serve specific purposes rather than being constant residences throughout the year.
Average Den Dimensions
Fox dens vary in size, but typical entrances are circular or oval, measuring about 6 to 12 inches (15 to 30 cm) in diameter. The tunnel leading from the entrance angles downwards at approximately 40 to 45 degrees. Red fox dens can extend significantly underground, with tunnel systems ranging from 25 to 75 feet (7.6 to 22.9 meters) in length. The main chamber, where a vixen might give birth and care for her kits, is located 3 to 10 feet (1 to 3 meters) below the surface.
Arctic fox dens, particularly those in the tundra, can be substantially larger and more complex. Some of these ancient den systems, passed down through generations, can cover an area of 11,000 square feet (1000 square meters) or more. A study in Svalbard found Arctic fox dens averaged 52.1 square meters (approximately 560 sq ft) with nearly 10 entrances.
Inside a Fox Den
Beyond the entrance, a fox den develops into a network of tunnels and chambers. These complex structures feature multiple entrances and exits, providing occupants with escape routes from predators. Some large den systems can have as many as 19 entrances for red foxes, while Arctic fox dens have been recorded with over 100 openings.
The tunnels connect to one or more main chambers, used for resting and raising young. Within the den, foxes create specific areas for different functions. This can include a main nesting chamber for the vixen and her kits, as well as separate dugout areas for storing excess food, known as caches. Unlike some other burrowing animals, foxes do not bring bedding material into their dens, resting directly on the earth. The multi-chambered design also contributes to better air circulation.
What Influences Den Size
Several factors contribute to the varying sizes and complexities of fox dens. The species of fox plays a significant role; for instance, Arctic fox dens are more elaborate and extensive than those of red foxes. This difference is partly due to the harsh environmental conditions in Arctic regions, where dens can be reused for hundreds of years by successive generations, leading to their immense size and numerous openings.
The type of soil and available terrain also influence den construction. Foxes prefer to dig in loose, well-drained soil, selecting slopes, ridges, or knolls that offer natural drainage and easier excavation. While foxes are capable diggers, they modify or take over existing burrows created by other animals, such as woodchucks, badgers, or rabbits. The age and experience of the fox constructing or maintaining the den also impacts its complexity, with older foxes creating more intricate structures.
How Foxes Use Their Dens
Foxes primarily use dens to raise their young, known as kits. The vixen gives birth and cares for her blind and deaf offspring within the den’s protective chambers. Kits remain inside the den for four to five weeks after birth, gradually venturing out as they grow.
Beyond the breeding season, adult foxes do not reside in dens year-round. They prefer to sleep in open, sheltered locations above ground. However, dens provide temporary refuge during periods of severe weather, such as heavy snowfall, or serve as quick escape routes from predators. Foxes return to the same denning areas annually, but may choose a different den within that territory based on its condition, past disturbances, or local prey availability.