By Kimberly Royar, Furbearer Project Leader, Vermont Agency of Natural Resources, and Brian O’Gorman, Tree Farmer
Many wildlife species rely on standing dead or dying trees for food, nesting, and cover. Natural den trees, especially those with cavities that may be in the vicinity of water, are valuable for everything from waterfowl, woodpeckers, and owls to bats, squirrels, marten, porcupine, raccoon, and fisher. Landowners can improve habitat for many wildlife species by retaining standing dead and dying trees in their woodlot. If possible, woodlot owners should manage for at least six living cavity trees or snags per acre with one greater than 18” in diameter and three larger than 16” in diameter. The priority is for hardwood trees over softwood to extend the
viability of the tree.
On lands where natural standing dead trees are limited, manmade nest boxes can be erected to subsidize the number of live den trees. Artificial ‘nest’ boxes have been constructed and erected to enhance habitat for many wildlife species, from bluebirds to bats, and have been used in
Minnesota for fisher to compensate for the lack of large diameter cavity trees (>20” DBH (diameter at breast height)). The University of Minnesota completed a pilot study in 2019 that found that only 2% of 10,000 trees surveyed were large enough for fisher to use. The study
documented use of the specially designed fisher nest boxes by barred owls, flying squirrels and other rodents, raccoons, and fishers.
In Vermont, a landowner and Tree Farmer in Bennington County, Brian O’Gorman, is experimenting with nest boxes for fishers (Pekania pennanti). Although today fishers are abundant throughout Vermont, they were extirpated in the 1800s due to extensive land clearing and unregulated harvest. They were reintroduced in the 1950s and 1960s by the Forest, Parks, and Recreation Department to control porcupine populations and continue to play an important role as a forest predator. They primarily reside in coniferous or mixed hardwood forests and exhibit a particular preference for areas with diverse structure, such as that found in an uneven-aged forest containing snags and multiple fallen trees (Noonan, 2006). These areas not only provide ample denning opportunities but also, more importantly, offer higher concentrations and varieties of prey. Fishers use multiple large trees with cavities as den sites (Powell, 1982). Research in Maine found that females used one to five natal dens between March and June. Ninety-four percent of the trees were hardwoods, 52% of which were aspen (Paragi et al., 1996). In British Columbia, maternal fisher den boxes have proven to enhance the fisher population in areas dedicated to industrial forestry.
O’Gorman manages a 300+ acre Tree Farm that, like many Vermont properties, was once a pasture for Delano sheep. After reforestation, it had been heavily logged by the previous owners. Since purchasing the property in southern Bennington County, O’Gorman enrolled in the Use Value Appraisal program (UVA or “Current Use”) and has been managing it according to a forest management plan. He has worked with his VT forester and a logger primarily for sugar maple production but also to improve and diversify the property for wildlife by planting butternut seedlings and red oak acorns, protecting and enhancing mast and old growth areas, and erecting artificial fisher nest boxes. O’Gorman built three boxes for fisher with the assistance of Vermont Trappers Association member, Al Zander, according to plans from British Columbia, Canada (Brinoni, 2015). O’Gorman and Zander distributed and erected two of the boxes into areas on his property, and the other onto Zander’s, with promising habitat and obvious fisher tracks and sign (Zielinski et al., 1995) with the help of a local Vermont ATV Sportsman’s Association (VASA) club. He has outfitted each with a camera set-up, baits, and lures so he can
monitor the comings and goings of the species using the boxes. So far, there is no evidence of use of the boxes by fisher, but O’Gorman will continue his efforts in hopes of improving habitat on his property for fisher and other wildlife species.
Kim Royar is a wildlife biologist with Vermont Fish & Wildlife Department.
Brian O’Gorman is a Tree Farmer and a member of the VT Trappers Association, and he encourages sportsmen to spend $15 and purchase a Vermont Habitat Stamp.
Brinoni, Michael AScT. Fisher Den Box Drawings prepared for Davis Environmental. Fish and Wildlife Compensation Program. Habitat Conservation Trust Foundation. 2015. 3 pages.
Noonan, Bob. 2006. Fisher Trapper’s Guide. Onalaska, WI. CPC Printing and Promotions. 95 p
Paragi, Thomas F., S. M. Arthur, and W.B. Krohn. Importance of Tree Cavities as Natal Dens for Fishers. Northern Journal of Applied Forestry, Volume 13, Issue 2, June 1996, Pages 79–83. https://doi.org/10.1093/njaf/13.2.79
Powell, Roger. 1982. Fisher: Life History, Ecology, and Behavior. Minneapolis, MN: University of Minnesota Press. 237 p.
Zielinski, William J.; Kucera, Thomas E., technical editors. 1995. American marten, fisher, lynx, and wolverine: survey methods for their detection. Gen. Tech. Rep. PSW-GTR-157. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 163 p.