The Ecology of the Pine Marten (Martes americana) at Sagehen Creek, California

DOCTORATE DISSERTATION: A study of the ecology of the pine marten (Martes americana) was conducted at Sagehen Creek, California from June 1981 through September 1983… Eleven marten were live-trapped … and fitted with radio collars…These data were used to investigate movement patterns, den use, and habitat preferences…When all data were considered, an activity peak in the early afternoon hours was observed. Males were more active than females at night. Marten were more active during the day in the snow-free season than they were during winter, but generally engaged in the same level of nocturnal activity year-round. …The average home range size was 1.39km square for males and 1.02km square for females. Extensive intra and intersexual overlap of home ranges was observed. Trees, snags, stumps and logs provided 77 percent of 210 marten dens located. Comparison with availability data indicated that snags, stumps and logs were preferentially selected as resting sites, but trees were underused in proportion to their availability. Stumps were used more often in summer. Snags and logs were used more in winter than in summer. …Den re-use was usually by the same marten first occupying the den, but in 4 instances a different individual used the den. Habitat was characterized …and…track plate surveys were completed... Thirty-five of 80 stations had marten visitation rates of over 40 percent… The presence of red fir (Abies magnifica), the absence of Jeffrey pine (Pinus jeffreyi), low solar incidence, and low snag density all contributed to higher marten visitation rates in the model. Discriminant function analysis separating sites used by marten from randomly selected sites developed a model... High basal area, downfall cover, living ground cover and log density characterized marten habitat…Data from the upper and lower Sagehen Creek basin areas were then analyzed separately. Higher basal area, downfall cover, and stump density characterized marten habitat in the upper basin. Higher basal area and downfall cover also characterized marten habitat in the lower basin, as did higher log density and lower percentage of litter ground cover. Shrub-regeneration cover was similar between active marten sites and random sites, but higher on marten rest sites…Prey availability by habitat type was investigated by trapping small mammals… Highest levels of deer mice populations were consistently found in brushfield habitat. Within forested habitats, highest levels of deer mice populations occurred in logged red fir forest and lodgepole pine forest. Chipmunks were evenly available throughout all habitat types. Mixed conifer forest had the highest number of ground squirrels in 3 of 4 trapping sessions. Montane voles were most abundant in large meadows and lodgepole pine forest. Mountain phenacomys were trapped in logged red fir forest, uncut mixed fir forest, and mixed conifer forest. Audio censuses of chickarees were conducted along small mammal trap lines…Chickarees were evenly available in all forested habitats in 4 of 5 censuses. One hundred marten scats were collected. The most common small mammal prey items, measured by percent frequency of occurrence in scats, were montane vole (10.6), chickaree (6.8), and chipmunk (5.8). Summer and winter diets of marten varied only slightly. Chickarees and chipmunks were similarly abundant in habitat preferred by marten and habitat not used by marten. Voles were not abundant in forested habitat, but occurred in relatively high numbers in meadows found within the forested areas frequented by marten. The smallest unit of marten habitat that should be considered by land use planners is 15km squared. Prime marten habitat is found in mature forests dominated by red fir, a mixture of red fir and white fir, and lodgepole pine with a total basal area of 30-60 m squared/ ha. Xeric, mixed conifer forests, especially forest dominated by Jeffrey pine, will not support marten. Downfall cover of 10-20 percent, stump densities of 50-90/ha, and log densities of 20-50/ha contribute to optimal marten habitat within the preferred forest types. Partial timber harvest in the form of selective cutting or small clear-cuts less than 1 ha might increase the suitability of an area for marten by providing more downfall cover in the form of large diameter slash and higher densities of stumps and logs if the site was not burned or intensively prepared for artificial regeneration. Small-area harvest may improve marten habitat, but the immediate effects of logging on marten are unknown. Radio-tagged marten should be monitored throughout the life of a timber sale to evaluate the immediate effects of logging.

博士学位论文：本研究于1981年6月至1983年9月间，在加利福尼亚州塞奇恩溪（Sagehen Creek）开展，针对美洲松貂（pine marten，Martes americana）的生态学展开系统性探究。
共计11只松貂被活体捕捉，并佩戴无线电项圈（radio collars）。研究依托采集所得数据，对其活动模式、巢穴利用行为及栖息地偏好进行了深入分析。综合全部观测数据可知，松貂的活动高峰出现在午后较早时段；雄性个体的夜间活跃度显著高于雌性。相较于冬季，松貂在无雪季节的日间活动更为频繁，但全年夜间活动的整体水平保持一致。
雄性松貂的平均家域（home range）面积为1.39平方千米，雌性为1.02平方千米；研究观察到大量的种内与雌雄间家域重叠现象。在所发现的210个松貂休憩巢穴中，树木、枯立木（snags）、伐桩（stumps）及倒木（logs）共提供了77%的巢穴位点。与生境可利用性数据对比可知，松貂优先选择枯立木、伐桩及倒木作为休憩场所，但对活立木的利用比例低于其在生境中的可利用占比。夏季中伐桩的使用频率更高，而冬季则更多使用枯立木与倒木。
巢穴再利用通常由首次占据该巢穴的同一只松貂完成，但有4次记录显示不同个体曾复用同一巢穴。研究对生境特征进行了表征，并完成了足迹板调查（track plate surveys）：80个调查位点中，有35个位点的松貂到访率超过40%。
模型分析显示，红冷杉（Abies magnifica）的存在、杰弗里松（Pinus jeffreyi）的缺失、低太阳辐射量以及低枯立木密度，均与更高的松貂到访率相关。基于区分松貂利用位点与随机选取位点的判别函数分析（discriminant function analysis），本研究构建了生境适宜性模型。松貂的典型生境特征表现为高胸高断面积（basal area）、高枯落物覆盖度、高活体地表覆盖度以及较高的倒木密度。
随后研究分别对上塞奇恩溪流域与下塞奇恩溪流域的数据进行单独分析：上流域的松貂生境特征为高胸高断面积、高枯落物覆盖度以及较高的伐桩密度；下流域的松貂生境同样具备高胸高断面积与高枯落物覆盖度，同时表现为更高的倒木密度以及更低的枯落地表覆盖占比。灌丛更新覆盖度在松貂活动位点与随机位点间无显著差异，但在松貂休憩位点上的占比更高。
本研究通过小型兽类诱捕，针对不同生境类型的猎物可利用性展开探究。鹿鼠种群的最高丰度出现在灌丛草地（brushfield）生境中；在森林生境中，鹿鼠种群的最高丰度见于采伐后的红冷杉林与扭叶松（lodgepole pine）林。花栗鼠在所有生境类型中分布均一。混合针叶林在4次诱捕周期中的3次均拥有最多的地松鼠。山地田鼠（montane voles）在大型草甸与扭叶松林中的丰度最高。山地攀鼠（phenacomys）的捕获位点包括采伐后的红冷杉林、未采伐的混合冷杉林以及混合针叶林。沿小型兽类诱捕线路开展了北美红松鼠（chickarees）的鸣声普查：在5次普查中的4次，北美红松鼠在所有森林生境中分布均一。
共计收集到100份松貂粪便样本。按粪便中出现频率占比统计，最常见的小型哺乳类猎物依次为山地田鼠（10.6%）、北美红松鼠（6.8%）以及花栗鼠（5.8%）。松貂的夏季与冬季饮食仅存在细微差异。北美红松鼠与花栗鼠在松貂偏好生境与非偏好生境中的丰度均无显著差异。田鼠在森林生境中并不丰富，但在松貂活动的森林区域内的草甸中数量相对较多。
土地利用规划者所应考虑的最小松貂生境单元面积为15平方千米。优质松貂生境见于以红冷杉为主、红冷杉与白冷杉混交，以及胸高断面积为30~60平方米/公顷的扭叶松林内。以杰弗里松为主的干旱型混合针叶林无法支撑松貂种群生存。在偏好的森林类型中，10%~20%的枯落物覆盖度、50~90株/公顷的伐桩密度以及20~50根/公顷的倒木密度，有助于形成最优的松貂生境。
若采伐地块未受火烧或未为人工更新进行高强度整地，采用择伐或面积小于1公顷的小型皆伐等方式开展部分择伐作业，可通过提供大径级采伐剩余物形成更多枯落物覆盖，并提升伐桩与倒木密度，从而提升区域对松貂的适宜性。小面积采伐或可改善松貂生境，但伐木活动对松貂的即时影响尚不明确。建议在整个木材采伐作业周期内，对佩戴无线电项圈的松貂开展全程监测，以评估伐木活动对松貂的即时影响。