Denning Ecology and Habitat Use by Fisher in Pine Dominated Ecosystems of Chilcotin Plateau


Fisher are part of the weasel family, and there are major information gaps on them and their use of habitats. The objective of this study is to fill in the knowledge gaps of fisher in BC concerning habitat use and reproductive denning in pine dominated habitats. Fisher are located  on the Interior Plateau of BC near Anahim Lake and Puntzi Lake, in which the lodgepole pine is the major plant species in the area. As well as researching the long-term effects of mountain pine beetle attack for forest management concerns, the study will help preserve fisher habitat by looking for new strategies. In Western North America, Fisher use old lodge-pole pine, Douglas-fir and trembling aspen for their dens.

In this study, one of the techniques used is radio- telemetry (system using radio signals to get information from one location to another) to monitor 24 Fisher. Reports have stated that Fisher home ranges are much larger in BC than anywhere else.

Additionally, fisher in BC are allegedly a blue-listed species and are vulnerable to over-trapping and habitat loss. Their preferred habitat for dens in the Chilcotin Plateau is the lodge-pole pine but around 80% of them are inclined to the mountain pine beetle attack which is affecting BC. This project will help forest managers as they will have more information and be able to provide new strategies that are essential for fisher habitats.


Forest wildlife and environment are affected by many changes and practices over time, human or natural. Loss of decaying old trees  influence animal habitat, such as the the diversity of cavity nesters. Therefore there is reduced fisher natal and maternal denning habitat in pine dominated  landscapes.

The reproductive dens used for the research were in cavities of large diameter trees. However, the trees used for reproductive dens purposes were smaller in diameter in Chilcotin compared to other areas in western North America. Generally, fisher use declining trees for their dens but can prefer trees in more advanced stages of decay too. The dens have been sighted in the southern part of the area, due to temperature preferences. The dens located in the south profit from warmer temperatures during late winter and early spring. Female fisher will tend to be in areas where prey abundance and diversity is, such as in riparian areas. Fisher have low reproductive output relative to their lifespan and low rates of juvenile survival.

Specific Objectives and Methods

There are three specific objectives that stand out, using three spatial scales which are stand, patch and element. The first one is to classify and label natal and maternal fisher denning habitat in the SBPS Biogeoclimatic Zone. Then, outline the abundance and spreading of maternal denning habitat elements within adult female fisher home ranges. Finally, contribute to help the forest management with recommendations of the Central Interior.

The methods used for this research are, first, the one stated before that is the radio-telemetry to collect data on locations of the dens between April and June (over three years). Second was radio tracking on females to locate natal dens. Third was to provide detailed descriptions of the landscape around the dens and area, climate report and the presence of prey.

Resulting in this research, 12 fisher out of the 24 were found dead due to the lack of  habitats. The dens were found in the larger trees of the located area, in heart rot cavities and usually in a live declining tree. The major trees used in the Chilcotin were lodgepole pine, trembling aspen and Douglas-fir, as the hard wood provides a better security against predators. What was also discovered, was that fisher dens are mainly found with a canopy cover range for protection but the fisher studied in the Chilcotin did not follow this pattern. The landscape plays an important part for the den choices such as the slope position and the abundance of food. The cavities are an important aspect of the ecological processes such as forest growth, disease and fire regime. They can also be used by other wildlife species when abandoned by fisher.

Radio-telemetry was used to locate rest sites, 105 of them were located between 2005 and 2008. Fisher use rest sites to protect themselves from predators and weather. Fisher require safe travel between dens and foraging, therefore explaining the location of their den. Unsustainable forest harvesting practises  may be destroying possible resting sites and additionally the beetle pine attack is another factor. It was discovered that fisher in BC compared to other part of North America used a greater proportion of terrestrial rest site (especially during winter time). Fisher are more inclined for habitats closer to streams.


In 2006 BC Conservation Data Centre had changed fisher status from S2 to S2S3, stating that the species is vulnerable to extirpation. This study has shown the different areas in which information gaps are, especially in areas of black cottonwood in the Chilcotin Plateau. The amount of pine trees affected by the pine beetle attack is around 46% but is predicted to go up to 70% by 2017, and this will accelerate forest harvesting turning mature pine forests (used for the dens) into younger stands, reducing fisher habitats and population in the area. This is why the study is important to fill in gaps as forest management will need all the information to supervise fisher population and the ecosystem. It is therefore important to protect the old stand of pine patches maintaining them to keep the eco-system going as it not only fisher that are using this kind of habitat. Finally, the author asserts that to maintain fisher habitat in the Chilcotin area deciduous and mixed deciduous have to be preserved, as well as keeping coniferous along streams. Locate and maintain old forest pines which include the lodgepole pine den trees ( in decay process but also snags are important). Douglas-fir trees should be kept and untouched in the area as to provide upland dening. It is necessary to avoid removing larger Douglas-fir, even when infested with the beetle pine. This is in order to keep the population of fisher in the area as well as sustaining the local ecosystem.

  • Source L. Davis, B. Columbia. 2009. Denning Ecology and Habitat use by fisher (Martes pennanti ) in pine dominated ecosystems of the Chilcotin Plateau.