Coastal British Columbia’s climate requires specific habitat features for black bears to successfully hibernate. Large, old trees and natural stumps historically provided safe black bear denning sites. However, forest harvesting often removes these critical features, reducing available dens for female black bears on the lower Sunshine Coast.
To address this, restoration efforts have focused on modifying legacy old-growth stumps to create potential black bear dens. These modified stumps aim to provide dry, secure locations suitable for hibernation during the winter months.
Black Bear Denning Site Requirements
Female black bears hibernate for approximately four to five months and require dens that protect them from wet conditions and external threats. Naturally hollowed bases of red and yellow cedar trees have traditionally met these requirements but are becoming less common due to logging and land development.
Restoration Process for Den Sites
Restoration involves selecting suitable legacy stumps left from historic hand logging operations. Modifications include:
- Cutting the stump’s top edge to solid wood.
- Installing a plywood sheet over the top to act as a roof.
- Carving an entrance at the base large enough for a female bear to enter.
- Adding bedding materials such as ferns inside the stump.
The goal is to replicate the protective characteristics of natural hollow tree bases to encourage use by bears.
Monitoring and Use of Restored Dens
Wildlife cameras are installed at den entrances to observe bear activity over multiple years. Initial findings show bears may take several visits before using the restored dens for hibernation.
Considerations and Future Work
Modern logging practices often remove tree bases, eliminating potential den sites. Legacy stumps from pre-World War II hand logging retain features necessary for restoration. Ongoing efforts focus on identifying such stumps in specific watersheds and expanding restoration work through volunteer participation.
Bear Dens Around the World
Bears use a variety of den types across the globe, depending on species, habitat, and climate. In North America, black bears commonly den in tree cavities, hollow logs, uprooted stumps, or beneath dense vegetation. In coastal British Columbia and Alaska, the bases of large, decaying red and yellow cedars are especially valuable as natural dens due to their insulation and shelter from wind and moisture.
Grizzly bears (brown bears) typically dig dens into hillsides, often on north-facing slopes that accumulate insulating snow. Dens are lined with vegetation and shaped to conserve body heat, especially important in regions with prolonged winter conditions. While some grizzlies reuse dens, most dig new ones each year to suit shifting terrain and cover availability.
Polar bears use a different strategy. Though most do not hibernate, pregnant females excavate dens in snowdrifts on sea ice or coastal tundra. These dens offer insulation from Arctic temperatures and are essential for birthing and protecting cubs during their most vulnerable months. The dens typically collapse in spring as the snow melts, and are not reused.
Outside North America, Asiatic black bears den in caves or hollow trees in forested mountain regions, while sloth bears in South Asia often use rock crevices, shallow burrows, or thick vegetation. In the Andes, the spectacled bear is known for creating leafy tree nests rather than using ground dens.
Den preferences vary by season, terrain, and needs. Maternity dens tend to be more secure and concealed, offering protection for cubs against predators and extreme weather. Bears generally avoid dens with poor drainage, high human disturbance, or exposure to wind. In some regions, bears may also use man-made structures or repurposed root systems when natural options are limited.
Dens are essential for energy conservation during hibernation, especially in colder climates. As habitats continue to change, the availability of suitable denning sites—particularly for females—remains a key factor in bear population health and regional wildlife planning.
Old-Growth Stumps as Bear Habitats
The reduction of old-growth denning sites due to forest harvesting has led to efforts to restore suitable habitats for black bears by modifying legacy stumps. Monitoring continues to evaluate the effectiveness of these restorations in providing functional hibernation dens.