The Humboldt Marten: Extinction Pending

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Wednesday, April 14th, 2010
Humboldt Marten at a bait station for observation in Six Rivers NF.

Humboldt Marten at a bait station for observation in Six Rivers NF.

The Humboldt marten, a sub-species of American pine marten, was historically known to range through out the coastal counties of Northern California, and museum specimens exist from the redwoods. The sub-species was thought to be extinct for around fifty years until 1995, when researchers found a small population of martens in Northern California living within the historic range of the sub-species in Humboldt and Del Norte Counties.

Recent genetics tests indicate martens in this relictual Northern California population are similar genetically to the museum specimens, as well as coastal marten in Oregon. Both coastal marten subspecies (M. a. humboldtensis and M. a. caurina) are genetically different from the Sierra population (M. a. sierrae) in Eastern California.

Survey results over the last 15 years demonstrate that the American pine marten is absent from large portions of its historical range, with the most severe loss within the range of the Humboldt marten. Most recent surveys (Summer 2008) for the Humboldt marten in Northern California show further reason for concern. While some sites that were previously occupied in 2000-2001 could not be re-visited due to wildfire and back burns, many previously occupied sites did not get detections in 2008. Survey data suggests a decline in marten occupancy at re-visited sites. Most of these sites had the poorest quality habitat. Survey data also suggests that there are currently less than 100 Humboldt marten left in Northern California, but that there could also be less than 50 individuals in this small isolated population. Martens are also absent from many areas of the historical range of M. a. caurina in Oregon.

There is serious reason for concern about the viability of small coastal populations of martens. Extinction in the very near foreseeable future is a very real possibility without protecting this sub-species. Multiple authorities voice concern about the status of marten populations in the Pacific states. The marten is designated as a species of special concern by the California Department of Fish and Game, a vulnerable species by the Oregon Department of Fish and Wildlife, a sensitive species by the U.S. Forest Service.

Populations of coastal martens in California and Oregon are small and isolated due to distribution of suitable habitat, effects of timber harvesting, and the historical effects of fur trapping. Fur harvests caused local and regional extirpations and declines and decades of protection from trapping have not resulted in the recovery of martens in coastal northwestern California. Martens can still be legally trapped in western Oregon.

Additionally, the species shows direct links to old growth forest attributes at multiple spatial scales. These attributes have and continue to be lost and altered due to the logging of mature and old growth forests. Very little is understood about how wildlife diseases and large-scale wildfires (and associated back burns) play a roll in the population viability of small isolated populations of coastal marten. Marten, like most mammalian carnivores, are also susceptible to many diseases that affect domestic dogs. These diseases could play a roll in the protection of small populations of martens. Vaccination of martens may be necessary to prevent extinction.

The protection of Humboldt marten from extinction could also potentially require Forest Service to consider the marten’s needs during wildfire season. This would make them more responsible to protecting den sites and considering the affects of large-scale catastrophic fires on the viability and ecology of coastal marten populations. Some marten habitat is created during a light burning of the forest, including new snags and cavities. However, the direct and indirect effects of a large-scale disturbance to the habitat of an extremely small meta-population of coastal marten could potentially cause the loss of that population.

This loss would have a corresponding decrease in the amount of genetic variability across the sub-species’ range. The effects of fires during the summer of 2008 within the habitat of the coastal marten have yet to be studied. As Green Diamond is one of many neighbors to the martens living in Northwest California, their current management scheme may be affected by listing the Humboldt marten. Protection of coastal marten populations in Oregon could close the trapping season for martens in Oregon.

Maintaining suitable habitat to encourage population expansion as well as enhancing functional landscape connectivity between meta-populations should benefit the coastal marten in California and Oregon. Conservation of marten populations will require protection of areas currently occupied and the evaluation of whether strategic restoration of additional habitat is warranted.