Certain criteria needs to be met for animals to make an area their home. We’ve seen this with bears choosing their dens for the winter and owls choosing their nesting sites. The same holds true for wolves when choosing their dens.
Each Spring, a site is chosen in which to build a den. We don’t know for sure who chooses the site, but most likely it’s the pregnant alpha female. They’ll usually choose a site on a slope that faces south, has dense vegetation and tree cover, and is close to water.
South facing slopes have a perfect angle for the sun to warm the soil and prevent deep snow building up near the entrance. Tree cover and vegetation offers protection from predators while proximity to water is a must for the mother and her pups.
Once a site is chosen, the pack works together to dig it. With everyone working together, a den can be created in a short amount of time. However, once it’s done and the alpha female enters it to have her pups, she goes in alone. No other wolf is allowed in to join her.
The den is used to keep the pups safe for the first several weeks of their lives. This is the only time the den is used. Once the pups are old enough to not need the den, it’s abandoned until the following year when the next litter of pups is due, or it may never be used again if another site is chosen.
Check out our article here to read more about dens and to answer the question: do captive wolves prefer different food depending on the season?