American marten (left) and its larger cousin, the Fisher (right).
The Fisher (Pekania pennanti) - an agile, mid-sized, slender mesopredator built for pursuing a diverse array of prey amongst mixed forests in Northern reaches of North America.
Its little cousin, the American Pine Marten (Martes americana) - slightly smaller and more charismatic, adapted to killing small rodents in boreal forests and mountainous conifer groves.
In areas where their territories overlap, the two species pass each other like furry little ships in the night.
Both members of the weasel family, fisher and marten tend to inhabit similar areas within their habitat range while competing with one another over valuable resources and food within that habitat. However, while the larger Fisher has managed to adapt immensely well to agricultural, suburban, and slightly more southern expanses of its home range, the marten is far more fickle with regard to altered habitat impact. Both species are particularly sensitive to forest management and climate changes, and as such, are considered to be integral ecological indicators of forest health in their respective habitat regions.
Trapper Input yields insight
According to reports from The Wildlife Society, fur trappers in Quebec have observed a shift in presence of both species over the past few decades; specifically - more fisher and less marten.
“Trappers are sentinels of changes that occur in the ecosystem,” says Pauline Suffice, a University of Quebec researcher who now works with the Quebec Trappers Federation. “Although they are not trained with the same methods as those used by wildlife managers, they are a kind of wildlife technician.”
Suffice is the lead author of a newly published study in the Journal of Wildlife Management which seeks to explore habitat impacts between fisher and marten, and determine any effects brought upon by habitat changes and climatic conditions on both populations in the Quebec, Canada region.
Being that both species have a respective fur market, and are a staple furbearer in the region, Pauline and her fellow researchers tapped trapper knowledge and insight to assist with their work.
“Our study confirms the importance of working with trappers to assess furbearing population trends in response to habitat changes and climatic conditions” the paper asserts.
Pauline and her team analyzed annual fisher and marten trapper harvest (number of pelts sold/100 km2) between the 1984-1985 and 2014-2015 trapping seasons, along with interviews to gather local knowledge from trappers as well as an extensive review of literature. The results were both insightful and robust.
Family Rivalry?
Side-by-side comparison of American Marten and Fisher distribution, both historical and present-day. (Images | USDA’s Historical Perspective on the Reintroduction of the Fisher and American Marten in Wisconsin and Michigan.
Both species saw dramatic declines throughout much of their range due to unregulated market hunting and extensive habitat loss from timber harvest in the 19th and early 20th Century. Fisher populations rebounded through the mid‐twentieth century in the eastern portion of the species’ range, particularly in the northeast US and Canadian provinces of Ontario and Quebec. Suffice’s study points out that fisher recovery is due to a mixture of translocation efforts, natural recolonization, habitat modification, and even beneficial effects from climate change.
The marten, on the other hand, has been much slower to fully recover in much of its southern range expanses. Regulated trapping of marten remains closed in northeast states like New Hampshire and Vermont; places just south of Quebec where the more-adaptable fisher continue to inhabit successfully.
Due to its significantly larger size, the fisher remains a dominant interspecific competitor of marten - and that competition, according to the study, contributes to the marten’s lack of strong presence in those shared territories on the southern fringes of its range. In addition to being a competitor for the same habitat and food as marten, the fisher is also known to be a direct predator of marten in areas where their ranges overlap.
Although depredation is integral, it isn’t the only aspect of transitional notoriety between fisher and marten populations.
A Product of Their Environment
Habitat, and by proxy, elements of climate, seem to heavily impact marten success, while the fisher has developed a far greater skill of adaptation.
American marten. (Photo | VT Fish & Wildlife)
Snow-pack and density, for example, can greatly influence both species in different ways. The marten is accustomed to high densities of fluffy snow, allowing access to the subnivean level (area between ground surface and snow cover) below the snow. This subnivean zone is a primary harborage area for prey species such as mice, squirrels and voles. While higher densities of fluffier snow (synonymous with colder, mountainous climates) work in the marten’s favor, snow-pack mixed with rain precipitation, forming a hard icy crust, allows for greater travel of fisher atop the snow’s surface.
While this snow crust reduces the marten’s accessibility to prey species, it also forces both species into greater exposure to predators. Snow compaction increases mobility of competing mesocarnivores such as coyote, bobcat, and red fox, and has the potential to further expose both marten and fisher to these predators, as well as others, such as raptors like hawks and owls. The odds play in the fisher’s favor, however, as the fisher is far more adapted to travel on snow crust, and large adult males are more apt to fend off would-be predators.
Rainfall also directly impacts both species in various ways. Early spring with cold rains can contribute to vulnerable fisher mortality, while cold rainfall during the winter impacts marten with the “snow crust effect” mentioned above, as well as exerting direct effects on marten thermoregulation. Due to fewer fat reserves, martens are more vulnerable to the cold when their fur is wet. Increased rainfall during winter months has the potential to incur greater mortality in martens.
Canopy cover was another factor. Both fisher and marten are attracted to coniferous and boreal growth, allowing for added shelter from precipitation and increasing mobility due to less snow cover. While the smaller marten is almost completely dependent on these conifer swaths, the fisher is far more at home in mixed forest habitat; favoring transition zones between conifer groves for shelter and rest, and slight accumulation of deciduous hardwoods for prey/food abundance.
“In our analyses, marten yields declined in the hardwood and mixed forest zones, where fisher yields had increased the most. In the coniferous forest zone, where increases in fisher yield were low, marten yield has yet to decrease.”
The larger fisher has also adapted somewhat well in the face of habitat loss; taking advantage of farm field and housing development edges, according to trapper testimony. The marten on the other hand, requires almost complete boreal and coniferous growth for survival - attributes which are found in greater amounts at the northern extent of the fisher’s typical range.
Fisher (Photo | VT Fish & Wildlife)
Suffice’s study does assert that changes in forest cover exerted stronger effects on fisher than did other climactic events, such as rainfall conditions.
The study also points out that conservation of interacting species at the boundaries of their ranges, such as the case with fisher and marten, may require extra attention from wildlife managers; in the form of specie response to future climates changes, and the possibility of adding levels of protection on currently existing landscapes.
My personal take away from the study - beneficial forest management is key.
The study further emphasizes the impact of rainfall on these two species, and a need for both dense coniferous tree cover to intercept rainfall and snowfall, as well as older established hardwood trees which can provide natural cavities for warmth and shelter.
Of course, strong communications with integral stakeholders is also important:
“Abundance of prey, competitors, and predators have been identified by trappers as major factors that may explain changes in fisher and marten abundance” the study notes, while also suggesting stronger relationships between governmental managers and local trappers.
“In addition, trappers could supply carcasses to researchers to help monitor long-term fisher and marten physical condition and reproductive success according to changing winter climate conditions” Suffice’s study suggests.
My home state of New Hampshire is one such place that has voluntarily enacted carcass turn-in of Fisher for several ongoing projects within the state. The carcass turn-in process is actually part of a multi-prong system of researcher interest; with USDA-APHIS, independent researchers at UNH, and NH Fish & Game staff all seeking insight for specific projects on fisher and other furbearers. The most recent string of tissue sampling was generated and funded by local hunters & trappers, amid local criticism of regulated trapping seasons and potential population declines (despite the indication that fisher appear to hold a strong presence just north of the NH state border in Quebec).
These projects, as well as the insight gathered in Quebec, continue with the assistance of researchers, wildlife managers, and licensed trappers in an attempt to gather more insight into fisher population dynamics throughout the region.
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Both members of the weasel family, fisher and marten tend to inhabit similar areas within their habitat range while competing with one another over valuable resources and food within that habitat. However, while the larger Fisher has managed to adapt immensely well to agricultural, suburban, and slightly more southern expanses of its home range, the marten is far more fickle with regard to altered habitat impact.