Assessment of short-term effectiveness of artificial resting and denning structures for the Humboldt marten (Martes caurina humboldtensis) in harvested forests in northwestern California

The Humboldt marten (Martes caurina humboldtensis) is a habitat specialist that requires large, old woody structures such as live trees, snags, and logs to provide suitable resting and denning locations. Many timber harvesting practices remove these woody structures and harvested forests typically have a poor availability of suitable resting and denning locations for martens. Artificial structures ("marten boxes") may increase the availability of resting and denning locations for martens in harvested forests by acting as surrogates for natural woody structures. Increasing the availability of resting and denning locations may improve suitability of harvested forest stands and thereby accelerate marten recolonization of harvested forests. In 2013, I deployed 55 marten boxes among three study sites in northwestern California. I monitored animal visitation and animal use with remote cameras at 43 boxes for approximately 12 months and detected 10 mammalian species. Douglas squirrel (Tamiasciurus douglasii) was the most common small mammal species and fisher (Pekania pennanti) was the most common carnivore species visiting boxes. Animal use of boxes (i.e., entering the box) was rare but was documented for four species, including marten. Track plate surveys conducted prior to box deployment indicated that the Goose Creek and Mill Creek study sites were not marten-occupied; however, naïve occupancy estimates at the two sites were significantly different for three out of five other carnivore species detected. Habitat transects revealed that Pecwan Creek, the marten-occupied site, had a significantly higher density of potential resting structures for martens than the Goose Creek or Mill Creek sites. Differences between study sites in terms of box visitation, species occupancy, and potential resting structure availability may be the result of different animal species assemblages, dominant forest types, forest management histories, or other processes. My data demonstrate visitation and use of boxes by martens; however, longer-term monitoring of boxes will likely be necessary to better understand their effectiveness as a conservation tool for the Humboldt marten.