2008 Forest Carnivore
Monitoring Summary
HFQLG Monitoring Program
Forest Carnivore Monitoring
In 2005, the Forest Service Pacific Southwest Research Station (PSW) (Zielinski et. al
2005) published a study that stated there was an apparent gap in marten occurrences
between the Lassen National Park and the Tahoe National Forest (Sierraville Ranger
District). The conclusion was based on surveys conducted in the area in the summers of
2000 and 2001. The results of these surveys were used to build a model to predict marten
occurrence in the southern Cascades of California (Kirk 2007, Kirk and Zielinski in
press). Kirk’s model used vegetation information and administrative boundaries to
predict occurrence and indicated a lower probability of marten occurring in many areas of
the Lassen National Forest (LNF) due to lower habitat values (relatively small amounts
of moderate to high quality denning and resting habitat).
Figure 1: Habitat Predictions Kirk 2007
Area where
martens have been
detected using
Lassen National
Forest protocol
surveys (unrelated
to the PSW
surveys).
In Figure 1 the dark green indicates high probability of occurrence and the lighter green indicates moderate
probability of occurrence. The red triangles indicate marten detections from the PSW surveys. The black
triangles indicate PSW survey points without marten detections. .
These two reports are in opposition to findings from protocol surveys completed over the
last decade on the LNF (marten have been noted to be generally absent from the Plumas
National Forest except within the Lakes Basin area). Importantly, the LNF surveys were
largely conducted in the winter using cameras and the PSW surveys in the summers using
track plates and cameras The discrepancy between the results of LNF and PSW surveys
has made the analysis of project effects on marten problematic in that the analysis can
either recognize that a major portion of the HF QLG Pilot Project Area is currently
predicted to have a low probability of occurrence or assume that, if the Kirk model had
included the Lassen National Forests survey data, much of the HF QLG area may have a
higher predicted value.
To resolve the discrepancy an experiment was initiated in 2007 for two purposes: 1) to
test the null hypothesis that there is no seasonal difference in marten detection rates and
2) a means to test the predictive occurrence model and make refinements if necessary.
The experiment used the same survey grids and the same survey device (cameras) and
protocol during each season (winter and summer), to control for and eliminate the
original differences between the PSW and LNF surveys. Areas chosen for surveys
included the areas where LNF surveys had previously found marten but where predicted
occurrence was low under the Kirk model. Ideally the results would help determine
whether martens have the same probability of detection each season, despite different
patterns of occupancy for each season. It will ultimately be important to know whether
martens that are detected on survey grids in winter, but not summer, are territory holding
individuals or dispersers. Of equal interest is the utility of the current predictive model.
Both PSW and the HF QLG Project Area would mutually benefit by carrying out
monitoring that would 1) discern the current status of marten within the Pilot Project
Area, 2) provide information that would refine the predictive model, and 3) address the
connectivity issues as discussed in the HF QLG FEIS (1999) and the subsequent
monitoring plan.
The study design consisted of three grids within areas where marten had been detected
during local surveys. One grid overlapped with Lassen Volcanic National Park to sample
areas where the Kirk model predicted marten occurrence. Each grid consisted of 20
baited camera stations approximately 1 mile apart. The grids were set up across the
Almanor and part of the Eagle Lake ranger districts. One grid extended from the Lassen
Volcanic National Park to the town of Mineral, California. The second grid was centered
around Swain Mountain, overlapping both the Almanor RD and the Eagle Lake RD,
Lassen National Forest, and the third grid was centered around Humboldt Peak, Almanor
RD. The study design required two seasons of surveys to determine status. Each grid
was sampled once in the summer and once in the winter with two of the grids sampled
again the following summer. The following table displays the number of camera stations
where marten detected by season (the actual number of martens detected was unknown)
Lassen National Park
Swain
Humboldt Peak
Summer 2007
4
1
1
Winter 2007-2008
10
12
13
Summer 2008
---
2
0
Using a software program called PRESENCE, the pattern of detections (i.e. “detection
histories”) at each camera station were analyzed to determine if there was a seasonal
variation in detecting martens that were present. Despite the seasonal difference in
number of camera stations with detections (see table above), the “detection histories” did
not reveal a statistically different probability of detecting martens in summer versus
winter. Importantly, however, program PRESENCE can only analyze the pattern of
detections of martens that were detected at least once. It is, of course, unknown whether
there are a subset of individuals that are not detected at all and whether this subset differs
by season. Given this assumption, the findings support the conclusion that martens that
are detected during the winter are not detected during the summer, either because they do
not survive there to be detected or because they are present but not attracted to bait or
lure. Additional research, using a radio-collared sample of animals, is the only way to
distinguish these possibilities.
Local biologists remain convinced that the seasonal difference is due to failure of martens
to be attracted to bait during the summer, rather than seasonal changes in demographics
or residency. Local biologists have long believed that marten are disproportionately
attracted to bait stations in the winter when food sources are scarce. The analysis model
(PRESENCE) assumes that all martens in the study area are detected at least once. If
they are, then program PRESENCE is capable of detecting seasonal differences in
detection probability. There is evidence in other studies to support the conclusion of
seasonal variation in food that would explain the seasonal variation in marten detections.
Bull (2007) found not only seasonal variations but also variations in prey selections
according to sex. In a study conducted in the early 1990s within the Swain grid, Ellis
(1995) not only found marten within the Swain study area (an area within the reported
gap) but also recorded reproduction. Finally, there have been numerous anecdotal reports
of marten during the summer within the area identified as a gap in distribution. Therefore
the question of marten status remains undetermined.
Because of the numerous conflicts in the data, PSW continues to work with Forests
within the HFQLG Pilot Project area to address this issue. Currently plans are being
made to take the next step and radio collar marten to discern status (distribution and
abundance), habitat use and, ultimately, the impacts that land management activities have
on marten.
References
Bull, E.L. 2007. Seasonal and Sexual Differences in American Marten Diet in
Northeastern Oregon. USDA Forest Service Pacific Northwest Research Station.
La Grande Oregon.
Burnett R.D., K.Maute, and D.Humple. 2006 Avian Monitoring in the Lassen National
Forest; 2005 Annual Report. PRBO Conservation Science. Stinson Beach, CA.
Ellis, L,1995. Habitat use patterns of the American marten in Lassen National Forest.
MS thesis, Humboldt State University, Arcata CA.
Kirk, T. A. 2007. Landscape-Scale Habitat Associations of the American Marten
(Martes americana) in the Greater Southern Cascades Region of California.
Masters Thesis. Humboldt State University. Arcata, California.
Kirk, T. A. and W. J. Zielinski. In press. Developing and testing a landscape suitability
model for the American marten (Martes americana) in the Cascades mountains of
California. Landscape Ecology.
USDA Forest Service. 1999. Herger Feinstein Quincy Library Group Forest Recovery
Act Final Environmental Impact Statement. Pacific Southwest Region.
Zielinski, W.J., R.L. Truex, F.V. Schlexer, L.A. Campbell, and C. Carroll. 2005
Historical and contemporary distributions of carnivores in forests of the Sierra
Nevada, California, USA Blackwell Publishing Ltd
www.blackwellpublishing.com/jbi