Ask the Biologist
SL
Written by Jeremy Heft, WERC Biologist
1. When are dens used? It is widely known that wolves dig dens, but the use of these underground structures are often misunderstood by many. Every spring, usually in early April after the snow has melted on the Southfacing slopes, a site is selected for the resident pack’s den. It is not fully understood who exactly chooses the site, but most likely the pregnant alpha-female has the duty. We do know most of the parameters for choosing a den site, however. Research supported by WERC and performed by Jon Trapp (MS Thesis, Prescott College, 2004), showed that the density of vegetation and tree cover, proximity to water, and aspect of the slope were the major selection criteria for wolves in Western North America. This means that a site densely covered with vegetation and woody debris makes the den less visible and subsequently hidden from
other predators. The close location of water is probably to ensure an easy availability to both the mother and newborn pups. Finally, the Southfacing aspect of the slope allows the sun to warm the soil of the den and decrease the likelihood of deep snow near the entrance. Through both wild and captive observations on wolves, we know that most members of the pack participate in digging the subterranean chambers. Wolves are great diggers, so when a team of paws works together, a large den can be excavated relatively quickly. This is just one of the ways the entire pack cooperates for the benefit of the pups. Dens are only used by pregnant wolves for shelter when birthing the annual puppy litter. Adult wolves never use dens for any other purpose throughout the year. Contrary to popular belief, they do not use them SL - FALL 2016
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