Ecology and Management of Martes on Private Timberlands in North Coastal California

Green Diamond Resource Company has conducted periodic studies of fishers on its California timberlands since 1994. A graduate study in 1994 and 1995 used track plates to investigate the distribution and habitat associations of fishers. Fishers were detected at 65 percent of the survey segments during both years combined but marten were not detected. A repeated track plate survey conducted a decade after the initial effort revealed the presence of marten west of a known population on public lands. An abbreviated track plate survey effort in 2006 again confirmed the presence of marten in the same area of the ownership and a potential expansion of the occupied area. During 2010 and 2011, we used remote cameras to survey 75 stations in a two km² hexagonal grid in the northern portion of the ownership. We detected fisher at 45 camera stations, marten at eight stations and both species at six stations. Marten are persisting in areas where we initially detected them in 2004, but additional studies are necessary to investigate habitat use, demographics, dispersal and interactions with competitors like the fisher.

Introduction

2003); however, the one remnant population in this region occurs in an area dominated by Douglas-fir (Pseudotsuga menziesii) and tanoak (Lithocarpus densiflorus) forest associations (Slauson and others 2007), with coast redwood associations limited to the western edge of the currently occupied range (Slauson and others 2007b). This population uses two structurally distinct forest types with a common link of dense shrub cover; one occurring on serpentine soils and one on more productive non-serpentine soils (Slauson 2003, Slauson and Zielinski 2007, Slauson and others 2007).

In California, fishers historically ranged from Marin County to the Oregon border, east to Mount Shasta and Lassen Peak and south through the Sierra Nevada mountains to northern Kern County (Grinnell and others 1937). Fishers currently exist in two disjunct populations in California: one on the west slope of the southern Sierra Nevada and the other in the Klamath Mountains and Coast Ranges of northwestern California (Zielinski and others 1995). There has long been a concern over habitat loss and alteration due to rapid harvest of mature and old-growth Douglas-fir forests (Rosenberg and Raphael 1986).

Both species have been petitioned for listing under state or federal endangered species acts. The United States Fish and Wildlife Service determined that the west coast population of fisher warranted protection under the Endangered Species Act, but were precluded from being added to the list of threatened or endangered species due to higher priority actions (USFWS 2004). The fisher was officially added to the candidate species list at the time of this ruling. The California Department of Fish and Game recently completed a comprehensive status review of fisher in response to a listing petition (CDFG 2010), but the species was denied protection under the state endangered species act. The Humboldt marten was recently petitioned for federal listing as a threatened or endangered species (Center for Biological Diversity and Environmental Protection Information Center 2010).

Study Area

Methods

Prior to 2010, no surveys were conducted with the specific objective of determining the distribution or habitat associations of marten on GDRCo’s ownership. However, our field techniques were equally suitable for martens. In 2010, we deployed remote cameras at stations centered on a two km² hexagonal grid randomly located on the ownership (Zielinski and others, 2007). We randomly selected units to sample, but also focused on areas where marten were detected during prior track plate surveys. We deployed cameras for a minimum of three weeks at each station. We baited stations with raw chicken and a commercial trapping lure (Caven’s Gusto Lure, Minnesota Trapline Products, Pennock MN) as an attractant. We baited and checked stations weekly with the general exception that some stations were baited and checked every other week due to complications with access due to weather or other demands on field personnel. During the pilot work in 2010, we tested several models of purchased and loaned cameras to assess reliability, ease of use, function and other important factors. In 2011, we began placing two RECONYX (RECONYX, Inc., Holmen, WI) cameras (models HC500 and PC800) at each sample unit. Cameras were located approximately three to five m and at right angles from the bait tree.

Results

We did not detect marten during the 1994 or 1995 track plate surveys. The repeat track plate survey conducted in 2004 yielded a total of six marten detections at four track plates on two segments in the Klamath region of the ownership. To confirm that the tracks recorded on the sooted track plates were indeed marten, we put a camera trap at select locations and obtained photographic evidence of marten. With the repeat of the track plate survey in 2006, we obtained a total of 13 marten detections at nine track plates on three segments. We also confirmed marten presence in 2006 with a camera trap.

We sampled 75 2-km² units with cameras between September 2010 and June 2011. We obtained photographic evidence of fisher at 45 stations (60 percent) and marten at eight stations (10.6 percent). Seven out of eight stations had multiple visits by marten. Fishers were detected at 75 percent of the stations with marten. The mean LTD for marten was 11 days (minimum = 5, maximum = 16 days).

Discussion

Our current knowledge of the marten on the study area is very limited. The lack of detections of martens during most surveys does not prove that they were absent, but the preponderance of negative data certainly indicated that martens were either very rare or absent over most of the study area. With the overall dearth of marten detections, it is obvious that we lacked the data to assess any trends in the marten population, and we are not able to draw any valid conclusions about habitat use. Presumably, the martens detected on GDRCo’s ownership in 2004 and 2006 were dispersers or peripheral residents from the core population to the east on public lands. It may be strictly coincidental, but the potential expansion of martens onto our study area occurred at the same time that the regional population of fishers was temporarily declining. Our surveys in 2004 indicated a potential decline in fisher abundance as evidenced by fewer detections relative to the other survey years. Matthews and others (2011) documented a decline in relative abundance of fishers from 1998 to 2005 on the neighboring Hoopa Valley Indian Reservation. Although we detected martens at track plates where fishers had been previously detected, no martens and fishers were detected at the same track plate during the same survey period in 2004. Fisher and marten were detected at only one track plate during the same survey period in 2006. While our survey results do not allow for a definitive assessment of the trend in the coastal marten population, it appeared as if martens were dispersing further from their core population during the mid-2000’s relative to the 1990’s. In addition, a marten was detected approximately 10km further to the west in Prairie Creek Redwoods State Park in 2009. Regardless of any potential localized expansion of martens within GDRCo’s ownership, it remains clear that the marten population was small and isolated to only a small portion of the ownership.

Our recent camera survey data suggests that fishers are relatively abundant within the Klamath region of the study and that they also overlapped the marten detections more than we observed during the prior track plate surveys. The negative interaction between fishers and martens has been noted in numerous locations throughout their range and the inverse relationship in abundance between the two species may be the result of this interspecific interaction. Although our sample size of marten detections was small (eight), we observed fishers at 75 percent of the cameras where marten were detected. We observed one bobcat (Lynx rufus) at a station where we also detected marten and fisher. However, our surveys were not designed to attract bobcats and likely do not accurately represent the abundance of bobcats present within the managed landscape. Forest management activities that encourage growth of other mesocarnivore populations may also be considered a threat to marten populations, as some of these species (e.g., fisher and bobcat) may opportunistically kill martens when encountered (Hamlin and others 2010). Loss, modification, and fragmentation of habitat are considered significant ongoing threats to the remaining population of martens in northwestern California (Hamlin and others 2010). Past timber harvest activities have eliminated much of the late-seral forests in coastal northern California, and due to the specialized habitat requirements of martens, such as large diameter live trees, snags, and logs, it would likely require decades of little or no timber harvest in large areas to develop habitat with the necessary structural characteristics to support martens (Hamlin and others 2010).

Slauson and others (2003) indicated that the marten should be considered a ‘highly imperiled taxon’ within the redwood region and that Redwood National and State Parks (RNSP) contains both the largest remnant patches and the largest total amount of old growth redwood forests. They concluded that the long-term persistence of martens within the coastal forests of northwestern California will likely require both the maintenance of areas currently occupied by martens and the expansion of their distribution. They further noted that expansion of the marten’s distribution would require the combined effects of the restoration of suitable habitat and functional landscape connectivity to enable recolonization of suitable, but currently unoccupied habitat. However, they went on to note the critical conservation dilemma that the restoration of forest habitats with the structural characteristics necessary to be suitable for martens may take decades while the small isolated extant population of coastal martens was at serious risk of losing genetic variation or elimination due to stochastic demographic or environmental events such as wildfire. This led Slauson and others (2003) to conclude that while restoration efforts within the coastal parks may eventually facilitate recolonization by martens, other conservation measures may be necessary to re-establish martens due to significant barriers created by large areas of primarily early-seral forest on private lands, the Klamath River and U.S. Highway 101.

Another proactive conservation option that could yield more immediate benefits to the marten population is human assisted dispersal. This approach would be similar to a reintroduction with the exception that limited evidence suggests that marten are currently capable of dispersing to the coastal parks. The marten observed in Prairie Creek Redwoods State Park in 2009 is presumably evidence of a naturally dispersing animal. However, natural dispersal of male and female martens is impeded by considerable ecological and anthropogenic barriers between the existing population and available habitat in the coastal parks. These barriers and the abundant mesocarnivore population on managed lands could constrain natural establishment of a population of martens in the coastal parks. If the martens we detected on private managed forests are reproducing, it may be possible to identify dispersers from this area and deliberately move them westward to suitable habitat on the coastal parks. This strategy is not without complexities that need to be thoroughly explored prior to implementation. For example, this project would likely involve multiple partners from federal, state, tribal and private organizations, a commitment to funding for implementation and monitoring, and some initial basic research such as investigations of dispersal of marten. It would also be prudent to evaluate species reintroduction guidelines in the context of this specific effort (IUCN 1998). Ideally, this collaborative action would increase survival of juveniles relative to that of natural dispersers, it would establish a viable population of martens within coast redwood habitat in the parks, and it could reduce the vulnerability of the population to stochastic events such as disease and wildfire.

References

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GENERAL TECHNICAL REPORT PSW-GTR-19x