Humbolt Martens at Risk

A study published early this April estimated the home ranges, density, population size, and viability of Humboldt martens (Martes caurina humboldtensis) in the Oregon Dunes National Recreation Area. At the same time, five conservation groups filed a petition asking the Oregon Department of Fish and Wildlife to amend its fur trapping rules to ban trapping of martens west of I-5 in order to reduce the risk of extinction of this unique population. 

Humboldt martens are distinct from the pine martens that many are familiar with. Related to minks and otters, adult Humboldt martens grow to be about 2 feet long and have large, triangular ears and a long, bushy tail. This photo was taken by a remote-sensored camera by Oregon State University’s Charlotte Ericksson as part of a study determining the extinction risk of Oregon’s central coast population.

While pine martens most often live in higher elevation forests that experience seasonal snow, Humboldt martens live in near-coast forests where such a phenomenon is largely absent. Instead of using snow for cover like their alpinist relatives, they rely on dense vegetation to provide them with protection from predators. Shrubbery like salal, Pacific waxmyrtle, and evergreen huckleberry also provide them with their food source: berries and berry-eating birds. 

The availability of a food source
year-round has likely allowed for denser populations of martens to live on the coast versus the mountains. However, even with this density, their population is small, and dangerously so. 

Researchers from Oregon State University and the United States Forest Service used a mark and resight technique to collect their data. This involved live-trapping martens and fitting them with radio collars and reflective tape that would set off remote cameras when they came in contact. 

Within the boundaries of the study, it was estimated that there are 71 adults in two subpopulations separated by the Umpqua River. These two populations are isolated from one another, as well as from other Humboldt marten populations, which occur as far south as the Northern Californian coast. This isolation reduces the transfer of genes between the populations, which may limit their ability to adapt to certain pressures.  

What’s worse, martens are relatively slow to reproduce as it is. At two years of age, they become sexually mature, and may have one to two kits per year afterwards. However, according to the study, there is only a 35 percent chance that an individual will survive to reproduce.

Being so isolated and slow to reproduce may not be as much of an issue in a world without human impact. But, the scientists who conducted this study approximated that the extinction risk for one of the subpopulations is 32-99 percent if two to three human-caused mortalities occur annually over the next 30 years. Currently, human-caused mortalities are frequent due to the presence of Highway 101 at the eastern edge of the martens’ range in the Oregon Dunes. Compounding these accidental mortalities is the fact that it is currently legal to hunt martens across the state for their fur.

This is precisely why conservation groups filed their petition. Nick Cady, the Legal Director with one of the conservation groups, Cascadia Wildlands, said that if ODFW were to make the amendment, it would be a step in the right direction: “People in Oregon care deeply about wild places and the critters that live in them…I don’t think the people of Oregon want fur trapping there.”

The ODFW Commission is required to respond to the petition at their August 3 meeting at the headquarters office in Salem, where the public is welcome to attend and give testimony. In the meantime, public comments will be accepted by the ODFW Commission and should be addressed via e-mail to odfw.commission@state.or.us. 

Cady also said that Cascadia Wildlands is planning a future petition to the state to include Humboldt martens on their list of threatened and endangered species. Currently, they are only listed as a sensitive species, which does not provide them with as much protection. Future actions by the conservation group may also include working with other state agencies, such as the Oregon Department of Transportation, to improve habitat connectivity over Highway 101. 

To read the scientific study and petition, respectively, check out the following links:

https://peerj.com/articles/4530/

https://www.cascwild.org/trapping-ban-sought-to-protect-imperiled-humboldt-marten/

By Ari Blatt

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