Clearcutting continues to be the dominant harvesting system across much of North America. Its environmental impacts have long been the subject of debate, but there’s a general consensus that this forestry practice results in a shift in the species inhabiting an area. In the years following a clearcut, grasses and shrubs thrive, providing browse for moose and deer. However, this short-term boon comes at the expense of some of the site’s previous residents. Furbearers such as weasels and marten depend on mature forest, both for concealment from predators and for den and rest sites in the form of coarse woody debris. On most clearcut sites, this debris is burned after harvest. But what if there was a way to prevent the displacement of some forest-dependent species by building habitat out of waste wood instead of burning it?

We spoke with Dr. Thomas Sullivan of the Applied Mammal Research Institute about his HCTF-funded project examining whether windrows constructed out of waste wood could reduce some of the negative impacts of clearcutting on small mammals.

HCTF: I understand that many furbearers are reliant on mature forest habitat, and will inevitably be impacted by clearcutting. Would you say your project is about making the best out of an imperfect situation for these species?

Sullivan: Yes: the overall goal here is to try and make these harvested sites more amenable to small mammals, particularly weasels, marten, and their primary prey species, red-backed voles. Marten in particular dislike the openings left by clearcuts, because they leave them vulnerable to predation by hawks and owls. As these openings continue to increase in size, we have to provide these animals some way to get from one section of uncut forest to another if we want to keep them on the landscape.

HCTF: For this project, you proposed that waste wood shaped into windrows could act as travel corridors for small mammals, allowing them to move across clearcuts to areas of intact forest. How did you test this idea?

Sullivan: We used a combination of live traps, scat analysis and predation events to compare small mammal presence in windrows constructed out of post-harvest woody debris to their prevalence on clearcuts where the debris was left distributed, both on sites near Golden and Merritt. What we found was that evidence of marten, weasels and red-backed voles was consistently higher in the windrows.

HCTF: Your results seem to support the idea that the relatively small labour investment required to construct windrows out of post-harvest woody debris could pay big dividends for wildlife, yet the majority of this debris is burned. Why?

Sullivan: Currently, foresters are legislated to deal with post-harvest woody debris: they have to get rid of it, either by burning or having someone agree to come and chip it up for biofuel feedstocks, with the latter only being feasible on sites near roads and processing plants. To my knowledge, the only way around this legislative requirement is if you build a variance into your silviculture prescription stating that you are going to leave some piles or windrows for habitat.

HCTF: What is the reasoning behind the current requirements around debris removal?

Sullivan: [The debris is considered] a fire hazard, even though there is absolutely no scientific evidence that these piles catch on fire by themselves. Once in a blue moon, up on a hilltop, you might get a lightning strike, but if there are any trees around, it’s far more likely to hit them. Any actual fire risk comes from humans who’d set them ablaze, which is why we probably don’t want to build windrows on sites near main roads. Far better to build them along deactivated roads or in the back country – and there’s certainly no shortage of this type of cut area. Before we can make windrows standard practice on these types of sites, there has to be a change in government policy, and that could take some time. I believe policy revisions have to follow what’s happening on the ground: we need to get as many foresters and companies trying out this method, even if it means going through a laborious variance process.

HCTF: Speaking of foresters, both Louisiana Pacific Corp. in Golden and Aspen Planers Ltd. in Merritt helped fund this study, along with HCTF. In the course of doing research on the effects of clearcutting on small mammals, have you found a significant difference in the effort that individual forestry companies are willing to expend to preserve wildlife habitat?

Sullivan: You know, the individuals are crucial. The silviculturalist with Louisiana Pacific in Golden has been instrumental in thinking in a broad-minded way. He is interested in anything that they can do to make the forest more diverse. Initially, this began as a business concern: he had a serious problem with the Microtis species of voles (the meadow voles and long-tailed voles) feeding on newly-planted trees, so he was very interested in anything that would increase the number of predators on his clearcut units.

HCTF: So building windrows to enhance predator habitat could be advantageous for foresters, as well as ecosystems?

Sullivan: Definitely. If you’ve got Microtis voles in your harvest area, it can be a serious problem. They’ll eat many of the seedlings – enough to necessitate replanting. There’s been a lot of work put into preventing the damage done by these species. Re-creating habitat to help maintain predator populations seems a logical solution.

HCTF: What about cases that are not so mutualistic: is there an appetite within the industry to adopt practices that conserve biodiversity, even if they don’t provide direct business benefits?

Sullivan: I think so, but again, it is company- and even individual- specific. For example, at Elkhart (our study site near Merritt), Aspen Planers have provided financial and in-kind support for this research, and they don’t have a problem with voles damaging trees. They are simply interested in what they can do to improve wildlife diversity. Again, this could be attributed to certain individuals’ philosophies, though I would say that the company policies of both of Aspen Planers and Louisiana Pacific are pretty positive in this direction.

HCTF: In one of your recent studies, you suggest that a habitat credit system, similar to current carbon offsetting programs, might provide the financial incentive necessary to encourage companies who are perhaps less-ecologically inclined to change their current practices. Can you elaborate?

Sullivan: Like it or not, we are enslaved by economics. The concept of assigning a dollar amount to ecological values leaves a bad taste in some people’s mouths, but I think we need to move there. Whether we call them habitat credits or biodiversity credits, it’s really about finding a way to recognize the importance of wildlife and habitats in an economically-driven system. We think of biofuel feedstocks as products from woody debris, why not small mammals?

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The Habitat Conservation Trust Foundation invests money from angling, hunting, trapping and guide outfitting licence surcharges into conservation projects across BC. You can read more about surcharge-funded projects here.

What’s furry, fierce and likes to dine on porcupine? It’s the fisher, Pekania pennanti, a member of the weasel family that is seldom seen in the wild, but is an important part of British Columbia’s carnivore community. Despite its name, fishers do not fish and are dependent on forests for all their life history needs. The fisher is blue-listed (threatened) in BC, largely due to habitat loss. Female fishers require large diameter trees with cavities to birth and raise their young. They will only use cavities with entrance holes that are approximately 8 – 12 cm in diameter: large enough for them to squeeze into, but small enough to keep larger predators away from their kits. Den trees also need to have other trees and shrubs around them to allow the female approach her den unseen. These specific requirements (along with the fact that females usually require multiple cavities to accommodate the growing kits) make fisher populations extremely vulnerable to extirpation through loss of suitable denning habitat.

In the Bridge River Watershed, north of Lillooet, BC, fisher habitat has been impacted by the creation of two large hydro-electric reservoirs, large-scale fires, mountain pine beetle, and an ongoing history of forest harvesting that is dominated by clear-cut systems. Understandably, there is concern about the combination of these habitat impacts on local fisher populations.

The Habitat Conservation Trust Foundation and BC Hydro funded a three-year project that would provide an accurate population estimate for fishers in the Bridge River watershed, as well as estimate the distribution, abundance, and supply of potential reproductive dens. In-kind support for this research was provided by the Lillooet Tribal Council, BC Ministry of Environment, and the BC Trappers Association.

Estimating Fisher Density

Fisher expert Larry Davis and his research team determined fisher density estimates using a winter hair snag survey. Davis explains: “We used sticky mousetrap paper to pull a sample of hairs from fishers that were attracted to traps baited with a chicken wing. Fishers trying to get the wing would press against the mousetrap paper and leave a hair sample behind for us to collect. We sent the samples to a laboratory specializing in wildlife genetics that identified the samples by species, sex, and individual identity.”

“Of course, we captured many other animals that went after the bait,” Davis continues. “We even had one wolverine chew the top half of the trap off.”

In the end, Davis and his team were able to identify 8 different fishers from the data, some of which were captured multiple times. The data was inputted into a computer program that used this information to estimate that there were 14 fishers in the 771-km² study area. This yields an estimate of 18 fishers per 1000 km²: relatively abundant when compared to estimates from elsewhere in BC.

“It’s important to note that this estimate is based on only one season of sampling and animal numbers can vary considerably between years,” clarifies Davis. “Also, only three of the 8 fishers sampled were females and some are likely to be young from last year’s litter or transient animals. Despite this caveat, Davis believes that “the Bridge River area supports a healthy population of fishers, and that a sustainable population can be maintained if important habitats, such as den sites, are retained in managed forests”

Estimating Available Denning Sites

To estimate the number of trees that would make suitable fisher den sites, Davis concentrated on areas where track transects had found fisher. Potential fisher den trees were identified as those meeting the following criteria:

• right species;
• large diameter stems; and
• the presence of a heart-rot decay cavity with an entrance hole 8 – 12 cm in size.

The “right species” criterion was based on previous research that found fishers using cottonwood, balsam poplar, trembling aspen, Douglas-fir, and lodgepole pine as den trees in BC. Common to these tree species is that they can have extensive heart-rot forming large internal cavities while the tree is still living. Other trees, such as spruce, also get heart-rot, but don’t maintain the hard exterior shell that preserves the standing tree and cavity for many years. The minimum tree diameter depends on the tree type, but is generally large for the particular tree species.

Davis and his team estimated the number of potential trees in the landscape by counting the number found in 1 hectare transects distributed across the study area.

“It turns out that trees meeting all our criteria are rare in the landscape,” says Davis. “Even in the ‘best’ habitat, there was less than 1 tree in 2 ha, and most forest types had much lower densities of potential den trees.” As Larry explains, the actual densities may be even lower still: “There is one additional criterion a fisher would have that we couldn’t easily check – the size of internal cavities. Cavities large enough for a female fisher and her kits are estimated at 25 – 30 cm in diameter, based on the size of an average female and internal measurements we have taken at fisher dens. Given this, fisher reproductive dens are likely to be much scarcer than we think, but our estimate provides a starting place for making recommendations to forest companies on targets for protecting fisher den trees.”

So how are these findings being used to inform fisher management? These results, combined with the findings of more than 20 years of fisher research in BC, have been used to create management recommendations and targets for fisher habitat. Davis and his colleagues have created a website summarizing this information at www.bcfisherhabitat.ca . For foresters and government, the website supplies targets on the amount of area and number of structures fishers need for breeding, resting, foraging, and movement habitats. This means tenure holders, such as trappers, can use this information to ask foresters how they are meeting fisher targets for logging operations on their trap lines.

“Fishers are a blue-listed species in BC, and forest professionals are legally required to manage landscapes to help maintain this species,” says Davis. “The website allows the BC Fisher Working Group an opportunity to continue working with trappers, government, the forest industry, and others to update and refine management strategies for fisher in a timely fashion.” Davis and his team have also created resources to encourage private landowners to preserve suitable den trees on their land (view). “Preserving these types of trees not only help fishers, it also benefits around many other native species reliant on them for their continued survival.”

Many thanks to Larry Davis for supplying much of the information and images for this article. In recognition of the fact that studies like this one indicate suitable fisher denning habitats are becoming increasingly rare, HCTF is currently funding a project to determine if artificial den boxes will be used by reproductive fishers, and the extent to which these devices might mitigate the loss of natural denning habitat. Check back here for future updates on this project.

View updates about this project>>

In the frozen wilderness of North-central BC, a small, furry head pops out from under the snow. Its fox-like profile stands out against a creamy orange bib of fur. In a flash, the animal’s long, lithe body and bushy tail spring from the powder. It is an American Marten (Martes americana), a medium-sized mustelid known for its tree-top acrobatics and cat-like curiousity. She boldly lopes across the snow towards a tasty morsel, conspicuously placed to entice her into a cage trap disguised with branches and straw. Marten are commonly trapped for their pelts, but this cage won’t spell her demise. Instead, she will become part of a ground-breaking study examining marten’s movements, and how they might be affected by forestry practices.

Shannon Crowley, a researcher with the John Prince Research Forest (co-managed by UNBC and T’laz’ten Nation), and his colleagues check the study traps daily: if they’re lucky enough to get a marten, they fit it with the latest in GPS collars before releasing it safely back into the forest.

“They’re tough little critters,” confides Crowley. “Based on our experiences capturing them, they’re not fearful at all. We’ve had marten in cage traps that we’ve released, only to have them come back moments later to steal a piece of bait sitting right next to us.”

Crowley and his colleagues are working on their second year of an HCTF-funded project to determine how marten populations are affected by salvage logging of Mountain Pine Beetle-ravaged stands. They are comparing the species’ use of logged and unlogged areas by remotely tracking the movements of their collared subjects.

“We’re working with very new technology,” explains Crowley. “Really, this study is pioneering the use of GPS collars light enough to go on an animal this size. To my knowledge, we and a group in Scotland are the only ones to have tried them on marten.”

The general rule of thumb for tracking collars is that they shouldn’t exceed 5% of an animal’s body weight. The collars used by Crowley and his team are below that threshold, sitting at around 3%.

“The marten really don’t seem to be bothered by them,” says Crowley. “We happened to get a video of one of the collared animals at one of our remote camera sites, and he was heading up into the trees, behaving very much like a typical marten.”

Above: Video showing typical marten behaviour. These curious creatures often travel under the snowpack, but are equally adept at climbing trees. See more videos of marten and other mesocarnivores filmed in the John Prince Research Forest at the end of this post. 

Crowley says the location data from the new GPS collars is a significant improvement over what they could previously obtain using radio units.

“We’re pretty impressed: we’re getting the kind of movement data that we could have never gotten in the past,” says Crowley. “Getting a location used to be very labour intensive, especially in harsh winter conditions. We would typically get about three locations a week. Now, we’re averaging between six and twelve locations a day.”

The increased amounts of data allow Crowley and his team to examine how marten are moving across the landscape at a much finer scale. “Previously, we could see where they were, but we couldn’t see how they got there. Now, we have a clearer picture of how they’re using different habitat types.”

Crowley’s team has been working closely with local forest company Conifex to compare martens’ response to different logging practices. Eventually, their results could be used to inform forest management decisions so as to reduce the impact on marten, as well as other species.

“Marten have proven to be really good indicators of ecosystem health,” emphasizes Crowley. “They’re generally associated with mature forests with lots of structural complexity, which are also important for animals such as woodpeckers and mule deer.”

Though Crowley’s marten study is a short-term project, the data collected will become an important component of a long-term monitoring program focused on mesocarnivores, a group that also includes fishers, river otters, foxes and Canada lynx.

“The mesocarnivores encompass a diversity of species that require different habitat types,” explains Crowley. “Studying one species alone can tell you something, but when you look at a bunch of them together, by inventorying and surveying in different habitats, they can give you a much better idea of what’s happening on the landscape.”

This level of understanding is particularly important when considering the rapid rate of environmental change associated with salvage logging. Though marten populations as a whole are thought to be stable in BC, they have become endangered or even extirpated from other jurisdictions through habitat loss.

“Research like this is really about taking preventative action, so that marten don’t become endangered in BC as a result of land use practices.” Crowley states.

Despite the economic pressures to maximize timber harvest, Crowley remains optimistic about the potential for this research to make a positive difference for habitat conservation. “Within the forestry industry, I think there’s definitely an appetite for finding ways to reduce impacts. Wildlife and habitat have definitely become part of the conversation, though we still have a long way to go before wildlife values are incorporated as a standard practice.”

The John Prince Research Forest is the largest research forest in North America, more than 32 times the size of Vancouver’s Stanley Park. Situated 50 km north of Fort St. James, the JPRF lies between Lakes Chuzghun (Tezzeron) and Tesgha (Pinchi)in traditional Tl’azt’en territory and provides research opportunities for UNBC staff and students and education and employment opportunities for the local community. Check out some of the other amazing wildlife footage captured by remote cameras in the forest (submitted to us by Shannon Crowley):

American Marten:

Canada Lynx:

Wolverine: