William J. Zielinski

Comparing Scat Detection Dogs, Cameras, and Hair Snares for Surveying Carnivores

Abstract Carnivores typically require large areas of habitat, exist at low natural densities, and exhibit elusive behavior—characteristics that render them difficult to study. Noninvasive survey methods increasingly provide means to collect extensive data on carnivore occupancy, distribution, and abundance. During the summers of 2003–2004, we compared the abilities of scat detection dogs, remote cameras, and hair snares to detect black bears (Ursus americanus), fishers (Martes pennanti), and bobcats (Lynx rufus) at 168 sites throughout Vermont. All 3 methods detected black bears; neither fishers nor bobcats were detected by hair snares. Scat detection dogs yielded the highest raw detection rate and probability of detection (given presence) for each of the target species, as well as the greatest number of unique detections (i.e., occasions when only one method detected the target species). We estimated that the mean probability of detecting the target species during a single visit to a site with a detection dog was 0.87 for black bears, 0.84 for fishers, and 0.27 for bobcats. Although the cost of surveying with detection dogs was higher than that of remote cameras or hair snares, the efficiency of this method rendered it the most cost-effective survey method.

Monitoring Martes Populations in California: Survey Design and Power Analysis

Fishers (Martes pennanti) and American martens (M. americana) have been protected from trapping in California since the mid-1900s, yet in portions of each of their historic ranges their numbers are extremely low, perhaps due to the effects of timber harvest. We propose a method capable of detecting declines in the occurrence and distribution of fishers or martens using baited track-plate stations. The proposed sampling unit is a small grid of stations that has a high probability of detecting animals when they are present. These multistation units are sufficiently spaced to meet the assumption of independence for a binomial model. We propose a stratified random sampling design with strata sampled for proportions of occurrence at discrete points in time. Stratification is based on variation in occurrence by region and is estimated from preliminary survey data. A previously pub- lished bias adjustment is applied to the proportion of units with detections to adjust for possible failure to detect resident individuals at a sampling unit. A Monte Carlo simulation model was developed to determine the sample size necessary to detect 20 and 50% declines, with 80% power, in the proportion of sampling units with occurrence. We assume a 10-yr sampling interval. Sensitivity analysis, using a range of values for means and standard deviations of strata proportions, determined that power was much more sensitive to changes in mean than the standard deviation. When the best current estimates of the fisher strata proportions were input for 10 strata (five regional and two habitat) in California, 115 and 17 sampling units per stratum were necessary to detect 20 and 50% declines, respectively. For some circumstances this sampling effort was also sufficient to achieve strata estimates with 5% error and to detect statistical differences between individual stratum proportions. The steps in the process of implementing a monitoring program for Pacific fishers in California are outlined as an example of the planning and preparation necessary to monitor changes in the distribution of a rare forest carnivore.

RESTING HABITAT SELECTION BY FISHERS IN CALIFORNIA

Abstract We studied the resting habitat ecology of fishers (Martes pennanti) in 2 disjunct populations in California, USA: the northwestern coastal mountains (hereafter, Coastal) and the southern Sierra Nevada (hereafter, Sierra). We described resting structures and compared features surrounding resting structures (the resting site) with those at randomly selected sites that also were centered on a large structure. We developed Resource Selection Functions (RSFs) using logistic regression to model selection of resting sites within home ranges, and we evaluated alternative models using an information–theoretic approach. Forty-five fishers were radiomarked, resulting in 599 resting locations. Standing trees (live and dead) were the most common resting structures, with California black oak (Quercus kelloggii) and Douglas-fir (Psuedotsuga menziesii) the most frequent species in the Sierra and Coastal study areas, respectively. Resting structures were among the largest diameter trees available, averaging 117.3 ± 45.2 (mean ± SE) cm for live conifers, 119.8 ± 45.3 for conifer snags, and 69.0 ± 24.7 for hardwoods. Females used cavity structures more often than males, while males used platform structures significantly more than females. The diversity of types and sizes of rest structures used by males suggested that males were less selective than females. In the Sierra study area, where surface water was less common, we found almost twice as many resting sites as random points within 100 m of water. Multivariate regression analysis resulted in the selection of RSFs for 4 subsets of the data: all individuals, Sierra only, Coastal only, and females only. The top model for the combined analysis indicated that fishers in California select sites for resting with a combination of dense canopies, large maximum tree sizes, and steep slopes. In the Sierra study area, the presence of nearby water and the contribution of hardwoods were more important model parameters than in the Coastal area, where the presence of large conifer snags was an important predictor. Based on our results, managers can maintain resting habitat for fishers by favoring the retention of large trees and the recruitment of trees that achieve the largest sizes. Maintaining dense canopy in the vicinity of large trees, especially if structural diversity is increased, will improve the attractiveness of these large trees to fishers.

Marten Habitat Preferences in the Northern Sierra Nevada

Marten were studied in the 40-km2 Sagehen Creek Basin in Tahoe National Forest, Nevada County, California. Elevations range from 1,880 to 2,620 m. Summers are short and dry with great diurnal temperature variations; winters are long and nocturnally cold, but with midday temperatures often above 0 C. Most of the 91 cm of annual precipitation falls as snow. Average winter snow pack is 112 cm at 1,950 m elevation and may be substantially deeper at higher elevations. Xeric areas are dominated by Jeffrey pine (Pinus jeffreyi) and mixed Jeffrey pine-white fir (Abies concolor) (Jeffrey pine associations). Mixtures of lodgepole pine (P. contorta) and white fir (mixed conifer associations) dominate below 2,050 m elevation (lower basin). Above 2,050 m elevation (upper basin), red fir (A. magifica) dominates, with admixtures of mountain hemlock (Tsuga mertensiana) and western white pine (P. monticola) (red fir associations). Moist areas, comprising about 5% of the drainage, are dominated by lodgepole pine and a dense cover of sedges, forbs, and willow shrubs (Salix spp.) (riparian lodgepole associations). Large brushfields resulting from wildfire cover one-third of the study area.

World Distribution and Status of the Genus Martes in 2000

The genus Martes is comprised of 7 species of martens, sables and fishers, most of them forest-dwelling animals with valuable fur, distributed throughout North America, Europe and Asia. The pine marten (Martes martes) is indigenous over most of Europe, from Mediterranean biotopes to Fennoscandian taiga, and to western Siberia and Iran. It is found in insular wooded areas, shrublands, and coniferous forests. The stone marten (M. foina) occurs from Mongolia and the northern Himalayas to most of Europe. It frequents forests, woodlands and pastures, and is expanding in suburban and urban areas. The sable (M. zibellina) occurs in Russia, Mongolia, China, North Korea, and Japan. Over most of its distribution, the sable inhabits coniferous taiga forests with late seral attributes. The yellow-throated marten (M. flavigula; including the Nilgiri marten, M. gwatkinsi) occurs in sub-tropical and tropical forests from the Himalayas to eastern Russia, south to the Malay Peninsula and Sunda Shelf to Taiwan. The Japanese marten (M. melampus) occurs in forests of the main Japanese archipelago and the Korean peninsula. The American marten (M. americana) occurs in large contiguous populations in forested habitats of North America north of 35° latitude. It is associated with mesic coniferous and mixed forests with overhead cover and structural complexity near the ground. The fisher (M. pennanti) occurs in large contiguous areas across Canada, and in disjunct areas within the United States, north of 35° latitude. Whereas the distribution of Martes significantly expanded in many parts of the world over the last 20 years, largely due to several reintroduction programs, many populations are threatened by habitat loss and alteration. There is a need to develop cost-effective survey methods, monitor populations and fur-harvest activities, and assess the effects of natural and anthropogenic disturbance agents on habitat use by Martes species.

Home Range Characteristics of Fishers in California

Abstract The fisher (Martes pennanti) is a forest mustelid that historically occurred in California from the mixed conifer forests of the north coast, east to the southern Cascades, and south throughout the Sierra Nevada. Today fishers in California occur only in 2 disjunct populations in the northwestern mountains and the southern Sierra Nevada. We studied the ecology of fishers in both populations (the north coast [Coastal] and southern Sierra Nevada [Sierra]) to characterize the size and composition of their home ranges, and to compare features between locations. Twenty-one (9 Coastal, 12 Sierra) of 46 radiocollared fishers were relocated frequently enough (>20 times) to estimate home ranges. The home ranges of males (X̄ = 3,934.5 ha) were significantly greater than those of females (980.5 ha), and the home ranges of females were significantly greater in the Coastal than in the Sierra area. The smaller home ranges in the Sierra were probably due to productive habitats rich in black oak (Quercus kelloggii). Midseral Douglas-fir (Pseudotsuga menziesii) and white fir (Abies concolor) types composed the greatest proportion (42.8%) of home ranges in the Coastal study area. The greatest proportion of home ranges in the Sierra study area were in the intermediate tree size class (60.7%), had dense canopy closure (66.3%), and were in the Sierran Mixed Conifer type (40.1%). These measures provide guidelines for managers who wish to influence landscape features to resemble occupied fisher habitat. The recovery of fishers in the Pacific States, however, will also require the consideration of microhabitat elements and characteristics of landscapes that might affect metapopulation dynamics.

Genetic Diversity and Structure of the Fisher (Martes pennanti) in a Peninsular and Peripheral Metapopulation

Abstract Evolutionary processes can be strongly affected by landscape features. In vagile carnivores that disperse widely, however, genetic structure has been found to be minimal. Using microsatellite DNA primers developed for other mustelids, we found that populations of a vagile forest carnivore, the fisher (Martes pennanti), exhibit high genetic structure (FST = 0.45, SE = 0.07) and limited gene flow (Nm < 1) within a >1,600-km narrow strip of forested habitat; that genetic diversity decreases from core to periphery; and that populations do not show an equilibrium pattern of isolation-by-distance. Genetic structure was greater at the periphery than at the core of the distribution and our data fit a 1-dimensional model of stepping-stone range expansion. Multiple lines of paleontological and genetic evidence suggest that the fisher recently (<5,000 years ago) expanded into the mountain forests of the Pacific coast. The reduced dimensionality of the distribution of the fisher in western coastal forests appears to have contributed to the high levels of structure and decreasing diversity from north to south. These effects were likely exacerbated by human-caused changes to the environment. The low genetic diversity and high genetic structure of populations in the southern Sierra Nevada suggest that populations in this part of the geographic range are vulnerable to extinction.

Using Forest Inventory Data To Assess Fisher Resting Habitat Suitability In California

The fisher (Martes pennanti) is a forest-dwelling carnivore whose current distribution and association with late-seral forest conditions make it vulnerable to stand-altering human activities or natural disturbances. Fishers select a variety of structures for daily resting bouts. These habitat elements, together with foraging and reproductive (denning) habitat, constitute the habitat requirements of fishers. We develop a model capable of predicting the suitability of fisher resting habitat using standard forest vegetation inventory data. The inventory data were derived from Forest Inventory and Analysis (FIA), a nationwide probability-based sample used to estimate forest characteristics. We developed the model by comparing vegetation and topographic data at 75 randomly selected fisher resting structures in the southern Sierra Nevada with 232 forest inventory plots. We collected vegetation data at fisher resting locations using the FIA vegetation sampling protocol and centering the 1-ha FIA plot on the resting structure. To distinguish used and available inventory plots, we used nonparametric logistic regression to evaluate a set of a priori biological models. The top model represented a dominant portion of the Akaike weights (0.87), explained 31.5% of the deviance, and included the following variables: average canopy closure, basal area of trees <51 cm diameter breast height (dbh), average hardwood dbh, maximum tree dbh, percentage slope, and the dbh of the largest conifer snag. Our use of routinely collected forest inventory data allows the assessment and monitoring of change in fisher resting habitat suitability over large regions with no additional sampling effort. Although models were constrained to include only variables available from the list of those measured using the FIA protocol, we did not find this to be a shortcoming. The model makes it possible to compare average resting habitat suitability values before and after forest management treatments, among administrative units, across regions and over time. Considering hundreds of plot estimates as a sample of habitat conditions over large spatial scales can bring a broad perspective, at high resolution, and efficiency to the assessment and monitoring of wildlife habitat.

Diet of Fishers (Martes pennanti) at the Southernmost Extent of Their Range

Fishers ( Martes pennanti ) in the mountains of Californias Sierra Nevada occur at the southwestern margin of their distribution and inhabit different forest types with different potential prey than elsewhere in their range. Two typical fisher prey, the snowshoe hare ( Lepus americanus ) and the porcupine ( Erethizon dorsatum ), are absent from our Sierra Nevada study area. We characterized the diet of fishers in the southern Sierra Nevada by analyzing the content of 201 feces (44 males: 157 females) collected either from trapped animals or from the rest sites of radio-collared animals. Mammals were the most frequent food item; however, unlike previous reports, reptiles (20.4% of feces) and insects (55.7%) were major components of the diet. We also sampled 24 feces for the presence of spores of hypogeous fungi (false truffles) and found that 91.7% had spores representing at least six fungal species. Diversity of the diet was indicated by the fact that remains of no single family of animal or plant group were found in >22% of feces. The fisher is reputed to be a habitat specialist in the late-seral mixed conifer-deciduous forests of the western United States. Perhaps it is for this reason that our data depict the species as a dietary generalist, for whom it may be necessary to forage on many of the animal, plant, and fungal species that occur in and near mature coniferous habitat.

The effect of intrauterine position on the survival, reproduction and home range size of female house mice (Mus musculus)

SummaryIn laboratory studies using albino house mice, a females prior intrauterine position can affect many postnatal physiological, morphological and behavioral characteristics. Females flanked by males in utero (2M females) exhibit more aggressive dominance than females flanked by females (OM females). Thus, wild 2M females may be most successful during peak population densities when their aggressive nature would allow them to displace other females from limited resources. 2M and 0M females and males delivered by cesarean section were individually marked and released as young adults on two occasions onto a “highway island” (the area enclosed by exit and entrance ramps at an interchange) to determine whether 2 M females have a competitive advantage over 0 M females in the field. Males were included to create realistic population structure; their intrauterine position was not a treatment. Feeding stations afforded individuals an opportunity to exhibit their dominance by maintaining home-ranges at or near the stations. The populations were monitored by periodic live-trapping and reproductive success was determined using field body weights and by post-mortem examination for uterine implantation scars. Survival and capture rates were estimated, using a modified Jolly-Seber markrecapture program, for each of four intervals between trapping occasions over the course of 7 weeks. There were no overall differences in survivorship between 2M and 0M females, neither type of female was caught more frequently at feeding stations and they did not differ in measures of reproductive success. However, 2M females had significantly larger home-range sizes than 0M females and thus space use may be a trait “masculinized” by prior intrauterine position. Although there are a number of life-history characteristics that differ between 0M and 2M females in the laboratory that we did not test specifically in the field, our findings and other features of wild house mouse biology suggest that prior intrauterine position does not have a strong effect on survival and reproduction in the wild.