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Fire suppression and logging have contributed to major changes in California’s Sierra Nevada forests. Strategically placed landscape treatments (SPLATS) are being used to reduce density of trees, shrubs, and surface fuels to limit wildfire intensity and spread, but may negatively impact fishers (Pekania pennanti). We used camera traps to survey for fishers among 1-km2 grid cells of forest habitat in the Sierra National Forest, California. We used single-season (n = 894 cells) and multi-season (n = 361 cells) occupancy modeling to evaluate responses of fishers to fuel reduction in the 5 years prior to camera surveys. We also assessed occupancy in relation to burn history, elevation, and an index of canopy cover. Camera traps detected fishers most often between 1380 m and 1970 m elevation, and fisher occupancy was maximized at 0.80 at 1640 m elevation. Probability of detection was higher after initial fisher detection, in habitats with high canopy cover, and when surveys were done in fall to spring. Fisher occupancy was positively linked to canopy cover, and trended lower among cells with higher levels of managed burning or forest fires within 25 years of surveys, and in cells where 5 years of cumulative disturbance from restorative fuel reduction was higher. Local persistence declined 24% in areas with more restorative fuel reduction (0–100% of a cell), but was not diminished by prior burning, or disturbance from extractive activities (tree removals for commerce or hazard mitigation). Reduced local persistence by fishers in areas with extensive restorative fuel reduction was likely temporary; evidence from other sources intimated that they would resume higher use within a few years of ecological recovery. The trend for lower occupancy in extensively burned forest cells suggested that forest fires reduced but did not eliminate foraging opportunities for fishers. We also found that wildfires increased in frequency in our study area after the 1980s, and recent fires may increasingly impinge on higher elevation forests with higher fisher occupancy. Forest fuel reduction likely imposes a more limited short term cost to fisher habitat use than previously believed, but less is known about the responses of resting or denning fishers to management disturbance. Fuel reduction treatments could be intensified below ∼1450 m elevation, which may reduce spread of fires into higher elevation forests where fishers are more common, and where denning is focused.

Fishers (Pekania pennanti) in the west coast states of Washington, Oregon, and California, USA have not recovered from population declines and the United States Fish and Wildlife Service has proposed options for listing them as threatened. Our objectives were to evaluate differences in survival and mortality risk from natural (e.g., predation, disease, injuries, starvation) and human-linked causes (e.g., rodenticide exposure [toxicants], vehicle strikes). We monitored survival of 232 radio-collared fishers at a northern and southern study site in the Sierra National Forest, California. We retrieved fisher carcasses, and used necropsy examinations to determine causes of death. We estimated survival and mortality rates using the Kaplan–Meier estimator and nonparametric cumulative incidence functions, respectively, and integrated risk-specific survival rates into a Leslie matrix to evaluate how population growth (λ) might improve if management can reduce mortality from any of the risks. We determined cause of death for 93 of 121 fishers, and annual survival was 0.69 for all fishers, and 0.72 for female fishers. Mortality rates were 19.5% for predation; 2.5% for disease, injury, and starvation; and 1.9% for toxicant exposure and vehicle strikes. Predation rates were similar between sexes, and relative risk was 51% lower in fall and winter compared to spring and summer. Combined mortality from disease, injuries, starvation, vehicle strikes, and toxicants was 4.4%, and 11 times higher for males than females. We estimated a base λ at the northern site of 0.96, which had the potential to increase to 1.03 or 1.11 if predation were reduced by 25% or 50%, respectively, whereas λ could increase to 0.97 in the absence of deaths from all other risks except predation. Predation was the dominant limiting factor in our study population, and was also the most common mortality risk for fishers in the 3 West Coast states (67%), followed by disease, injury, and starvation (12%) and vehicle strikes (8%). Direct mortality from toxicants appeared limited to fishers in California. Our results identified the need for continued and potential expanded restrictions on habitat disturbance in fisher denning habitats. Research is needed on contact rates between larger predators and fishers, including whether fishers are more vulnerable to attack in open forests or along roads used by coursing predators. © 2015 The Wildlife Society.

In the west coast region of the United States, fishers (Pekania pennanti) exist in 2 remnant populations—1 in northern California and 1 in the southern Sierra Nevada, California—and 3 reintroduced populations (western Washington, southern Oregon, and northeastern California). The West Coast Distinct Population Segment of fishers encompassing all of these populations was proposed for listing as threatened by the U.S. Fish and Wildlife Service in October 2014. There are likely fewer than 500 total fishers in the southern Sierra Nevada population isolate, but empirical data on demographic rates, population size, and population growth are almost entirely lacking. Our goal was to estimate demographic parameters and current abundance of a fisher population at the north margin of the southern Sierra Nevada region. Radiocollared fishers were monitored from 2007 to 2013 to estimate survival and demographic rates, and camera traps were used to estimate population size based on detections of individual animals in a capture– mark–resight (CMR) framework. A Leslie matrix model was used to estimate a deterministic population growth rate (λ). Fisher abundance ranged from 48 animals in 2010 to 62 animals in 2012, whereas mean population density varied from 0.075 to 0.096 fishers/km 2 . Reproductive status was determined for 89 of 93 total denning opportunities; denning and weaning rates were estimated at 84% and 70%, and litter size was 1.6 kits. We documented 8 den failures, mostly associated with predator attacks. Demographic rates in the study population were comparable to reports from elsewhere in California or Oregon, but the CMR-based population density was the lowest reported in the United States. The estimated λ for the population was 0.966 (range 0.786–1.155), which was in agreement with no indication of a positive or negative trend in population density. An encouraging result from sensitivity analyses was that minor improvements in fisher survival and fecundity, facilitated by proposed mitigation or management to reduce exposure to several agents of mortality, could improve λ to 1.06–1.09 over the longer term. We believe that the combination of a population growth rate slightly below 1.0, small population size and low density, multiple challenges to survival and reproduction, and damage to habitat from wildfires warrants concern for the viability of the fisher population in our study area, which may extend to the overall southern Sierra Nevada population if λ trends below 1.0 in other parts of the region. There is a need for continued monitoring and potential mitigation for threats to survival to assure continued presence of fishers in the southern Sierra Nevada, California.

Interspecific killing is common among carnivores and can have population-level effects on imperiled species. The fisher (Pekania [Martes] pennanti) is a rare forest carnivore in western North America and a candidate for listing under the United States Endangered Species Act. Interspecific killing and intraguild predation are poorly understood in fishers and potential threats to existing western populations. We studied the prevalence and patterns of interspecific killing of fishers in the southern Sierra Nevada and Coastal Range of California. We collected forensic evidence and samples from the carcasses and predation sites, conducted full necropsies when possible, and used molecular methods to determine species of predators responsible for killing fishers. We recovered 101 (59 female, 42 male) fisher carcasses; for 62 (61%) carcasses, we attributed cause of death to interspecific killing. We found that bobcats (Lynx rufus, n = 25 fisher mortalities), mountain lions (Puma concolor, n = 20), and coyotes (Canis latrans, n = 4) were predators of fishers in our study areas. Bobcats killed only female fishers, whereas mountain lions more frequently killed male than female fishers, confirming our hypothesis that female fishers would suffer lethal attacks by smaller predators than would male fishers. Coyotes rarely killed fishers. We found differences in pathologic characteristics of the predation events among the 3 predator species, which may be helpful in identifying predator species. © 2014 The Wildlife Society.

Secondary exposure of wildlife to pesticides has been well documented, yet exposure is typically associated with agricultural or wildland-urban interface areas. Wildlife in undeveloped areas is generally presumed free from risk. In 2009, a male fisher was found dead in the Sierra National Forest and subsequent necropsy revealed that the animal died of acute rodenticide poisoning. Follow-up testing revealed that 85% of fisher carcasses recovered by two research projects in the previous three years tested positive for rodenticides. Concern arose that exposure could predispose an animal to mortality from other causes, and that the underlying role of toxicants would escape notice. Further investigation indicated that the most likely source was the numerous illegal marijuana cultivation sites currently found on public lands throughout the western United States. To determine whether the presence of cultivation sites predisposed fishers to mortality from other sources, we related survival rates to the presence and number of cultivation sites found within that animal’s home range over the past 10 years. Likelihood of exposure was related to the presence of cultivation sites, and female fisher survival was influenced by the number of cultivation sites within its home range. We discuss the conservation implications of this unexpected relationship.

Developing efficient monitoring strategies for species of conservation concern is critical to ensuring their persistence. We have developed a method using camera traps to estimate density and survival in mesocarnivores and tested it on a population of fishers Martes pennanti in an area of approximately 300 km2 of the southern Sierra Nevada mountains in California. Fishers in this region are isolated from other populations by a gap of approximately 400 km, and the status of individual populations in the southern Sierra Nevada is poorly understood, making management decisions difficult. We caught fishers in live traps, marked them with ear tags, and resighted them with camera traps. We measured latency to first detection and detection rate to compare our results to previous camera trapping studies of fishers. We used the robust design Poisson log-normal mixed-effects mark-resight model to obtain annual estimates of density and apparent survival. Our values for latency to first detection and detecti...

Many western conifer forests were historically affected by frequent, low- to mixed-severity fires. A legacy of fire suppression, logging, grazing and other factors has created current forest habitats that do not reflect historical conditions. The increasing size, severity, and costs of catastrophic forest wildfires are now focusing wildland management and research towards proactive fuel treatments designed to reduce fire hazards across landscapes. As part of the National Fire and Fire Surrogate (FFS) study, we researched the effects of three fuel treatments on small mammal populations within Sierra Nevada mixed-conifer forests. Twelve mixed-conifer stands were selected randomly from a set of available stands. Each stand was assigned to one of four treatment groups: controls, prescribed fire only, mechanical only, and mechanical plus fire combined. Abundance of California ground squirrels (Spermophilus beecheyi), long-eared chipmunks (Tamias quadrimaculatus), brush mice (Peromyscus boylii), and deer mice (Peromyscus maniculatus) were monitored both pre- and post-treatment. Only the deer mouse had a significant treatment effect. Deer mice abundance significantly increased from pre- to post-treatment within fire only and mechanical plus fire treatments, and declined within mechanical only treatments. All four species had a significant effect of year, with higher overall abundance in the post-treatment period. In addition to the experimental analysis, models containing stand-level covariates of vegetation and fuel characteristics were examined and compared using model selection procedures. The models only improved upon the experimental analysis for the brush mouse. Brush mice were found to have a positive association with stand-level canopy cover. Our results suggest that burning had a positive effect on deer mice and that mechanical only treatments had a negative effect. For the other three species, the dominant effect of year suggests that other, more regional factors may have affected abundance. Possible explanations included an increase in precipitation from pre- to post-treatment, a major cone crop in 2002, and a major decline in gray fox (Urocyon cinereoargenteus) occurrence. For the brush mouse, an evaluation of trap locations within stands indicates that this species was associated with dense clumps of tan oak (Lithocarpus densiflorus) or riparian areas. Leaving areas of dense low vegetation cover may benefit this species where fuel reduction treatments are implemented. Our study only documented the immediate impacts of fuel treatments and more research is needed to determine if our results will persist through time.

We estimated bobcat (Lynx rufus) density for 3 different locations in northern California using active infrared-triggered cameras. Using differences in pelage pattern as well as other physical characteristics, we identified individual bobcats from photographs, and used mark-recapture techniques to estimate population density. Camera density affected the precision of population estimates. The same population was estimated using camera densities of 0.5, 1, 2, 4, 6, and 8 cameras ⋅ km-2. Higher camera densities resulted in more captures and recaptures of bobcats and, conse- quently, in more precise density estimates. Similarly, the number of photo-captures and recaptures increased with increasing study duration. Increasing the area sampled resulted in the capture of more individuals but did not increase the percentage of recaptures. While some locations captured multiple bobcat photographs (e.g., 15 at 1 station), these photos tended to be recaptures of the same individual. There were no more than 2 individuals photo-captured at any 1 camera location. Bobcat density varied among habitat types as predicted. We estimated density as 0.27 bobcats ⋅ km-2 (s = 0.16) overall in an area in the northern Sacramento River Valley and as 0.35 bobcats ⋅ km-2 (s = 0.56) in a steep and rocky canyon within the area. At a 3rd site in the Coast Range, the estimate was 0.39 bobcats ⋅ km-2 (s = 1.44). Bobcats were more diurnal where human activity was less common. In addition, photo-capture was significantly higher along roads and trails without an attractant than it was off-trail with an attractant.

Remote cameras are an increasingly important tool in management and wildlife studies. However, we often do not know if they provide an unbiased sample of populations. Using a marked, radiocollared population of coyotes (Canis latrans) of known social status, we evaluated the influence of temporal (daily and seasonal) and spatial (distance between units, habitat, and proximity to human structures) factors on vulnerability to photo-captures. During 8 unbaited camera sessions of 6 weeks each, we obtained 158 coyote photographs at a photo-capture success rate of 1.6%. We were able to identify not only marked individuals, but also a number of uncollared adults through variation in their pelage. Photo-capture of adults peaked 2 weeks after we established camera stations. Annual success for photographing adult coyotes was greatest during March and April, which corresponded with the dispersal season. The majority of photo-captures occurred at night, and adult photo-captures peaked around midnight, with s...

California is home to both the native state- threatened Sierra Nevada red fox (Vulpes vulpes ne- cator), which historically inhabited high elevations of the Sierra Nevada and Cascade mountains, and to multiple low-elevation red fox populations thought to be of exotic origin. During the past few decades the lowland populations have dramatically expanded their distribution, and possibly moved into the historic range of the native high-elevation fox. To determine whether the native red fox persists in its historic range in Cali- fornia, we compared mitochondrial cytochrome-b haplotypes of the only currently-known high-elevation population (n = 9 individuals) to samples from 3 modern lowland populations (n = 35) and historic (1911-1941) high-elevation (n = 22) and lowland (n = 7) populations. We found no significant popula- tion differentiation among the modern and historic high-elevation populations (average pairwise FST = 0.06), but these populations differed substantially from all modern and historic lowland populations (average pairwise FST = 0.52). Among lowland populations, the historic and modern Sacramento Valley populations were not significantly differentiated from one another (FST = -0.06), but differed significantly from recently founded populations in the San Francisco Bay region and in southern California (average pairwise FST = 0.42). Analysis of molecular variance indicated that 3 population groupings (mountain, Sacramento Valley, and other lowland regions) explained 45% of molecu- lar variance (FCT = 0.45) whereas only 4.5% of the variance was partitioned among populations within these groupings (FSC = 0.08). These findings provide strong evidence that the native Sierra Nevada red fox has persisted in northern California. However, all nine samples from this population had the same haplotype, suggesting that several historic haplotypes may have become lost. Unidentified barriers have apparently prevented gene flow from the Sacramento Valley population to other eastern or southern populations in California. Future studies involving nuclear markers are needed to assess the origin of the Sierra Nevada red fox and to quantify levels of nuclear gene flow.

Wildlife populations of conservation concern are limited in distribution, population size and persistence by various factors, including mortality. The fisher (Pekania pennanti), a North American mid-sized carnivore whose range in the western Pacific United States has retracted considerably in the past century, was proposed for threatened status protection in late 2014 under the United States Endangered Species Act by the United States Fish and Wildlife Service in its West Coast Distinct Population Segment. We investigated mortality in 167 fishers from two genetically and geographically distinct sub-populations in California within this West Coast Distinct Population Segment using a combination of gross necropsy, histology, toxicology and molecular methods. Overall, predation (70%), natural disease (16%), toxicant poisoning (10%) and, less commonly, vehicular strike (2%) and other anthropogenic causes (2%) were causes of mortality observed. We documented both an increase in mortality to (57% increase) and exposure (6%) from pesticides in fishers in just the past three years, highlighting further that toxicants from marijuana cultivation still pose a threat. Additionally, exposure to multiple rodenticides significantly increased the likelihood of mortality from rodenticide poisoning. Poisoning was significantly more common in male than female fishers and was 7 times more likely than disease to kill males. Based on necropsy findings, suspected causes of mortality based on field evidence alone tended to underestimate the frequency of disease-related mortalities. This study is the first comprehensive investigation of mortality causes of fishers and provides essential information to assist in the conservation of this species.

Rio Grande wild turkeys (Meleagris gallopavo intermedia) were evaluated as potential hosts of ixodid ticks, lice, and Lyme disease spirochetes (Borrelia burgdorferi sensu lato [s.l.]) in three state parks in Sonoma County, California, USA, during 2003 and 2004. In total, 113 birds were collected, 50 (44.2%) of which were found to be infested by 361 ixodid ticks representing three species: the western black-legged tick (Ixodes pacificus, n=248), the rabbit tick (Haemaphysalis leporispalustris, n=112), and one American dog tick (Dermacentor variabilis). Year-round the prevalence of all ticks combined was unrelated to the age or sex of turkeys, and the prevalence of infestation by I. pacificus (35.4%) was significantly higher than it was for either H. leporispalustris (14.2%) or D. variabilis (0.9%). The proportion of the two prevalent tick species differed significantly by life stage with 86.3% of the I. pacificus and 82.1% of the H. leporispalustris enumerated being nymphs and larvae, respectively. Three species of lice were collected, including the chicken body louse Menacanthus stramineus (12.5% of total), Chelopistes meleagridis (37.5% of total), and Oxylipeurus polytrapezius (50% of total). The records for all three ticks are the first ever from wild turkeys, and those for the lice are the first from this host in the far-western United States. Wild turkeys potentially were exposed to the feeding activities of I. pacificus nymphs infected with B. burgdorferi s.l. as 15% of host-seeking nymphs (n=200) collected in woodlands used by turkeys as roosting or foraging areas were infected mainly with B. burgdorferi sensu stricto (s.s.). However, only one (1%) of 90 turkey blood specimens tested by PCR contained B. burgdorferi s.s., and four in vitro, complement-protein assays demonstrated that domestic turkey serum is moderately bacteriolytic for this spirochete. Taken together, these findings indicate that wild turkeys are important avian hosts of I. pacificus nymphs, but they appear to be inconsequential hosts of B. burgdorferi s.l.

This paper examines the severity of livestock depredation by coyotes (Canis latrans), reviews evidence implicating breeding (or “alpha”) coyotes in the majority of incidents, evaluates currently used depredation control techniques, and suggests directions for future research. Nonlethal control ranges from varied animal husbandry practices to coyote behavioral modification or sterilization. These methods show significant promise but have not been proven effective in controlled experiments. Therefore, many livestock producers rely on lethal control, and most employ nonselective strategies aimed at local population reduction. Sometimes this approach is effective; other times it is not. This strategy can fail because the alpha coyotes, most likely to kill livestock, are the most resistant to nonselective removal techniques. An alternative is selective lethal control. Livestock Protection Collars (LPCs) and coyote calling are the primary selective lethal approaches. However, LPCs do not have support from the general public due to the toxicant used, and the factors affecting the selectivity of coyote calling have not been studied. The greatest impediments to effective coyote depredation management currently are a scarcity of selective control methods, our lack of understanding of the details of coyote behavioral ecology relative to livestock depredation and wild prey abundance, the absence of solid research examining the effectiveness of different control techniques in a variety of habitats and at multiple predation intensities, and the dearth of rigorous controlled experiments analyzing the operational efficacy of selective removal versus population reduction.

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 (X = 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.

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.

The primary objective of this study was to develop a better understanding of coyote (Canis latrans) wariness particularly as it related to social status. We determined that territory status (controlling alpha, resident beta, or nonterritorial transient) affected vulnerability to photo-capture by infrared-triggered camera systems. All coyotes were wary of cameras, leading to relatively low numbers of photo-captures, most of which occurred at night. Alphas were significantly underrepresented in photographs and were never photo-captured inside their own territories. Betas were photographed inside and outside their territories, whereas transients were most often photographed on edges of territories. Both alphas and betas were photographed more often on territorial edges when outside their territories. We next addressed the question of how alphas were better able to avoid photo-capture. Alphas tracked human activity within their territories and presumably learned the locations of cameras as they were being set up. They did this either by approaching our location directly or by moving to a vantage point from where they could observe us. Betas and transients either withdrew or did not respond to human activity. Trials in which a dog was present were more likely to elicit an approach response from alphas. Avoidance of camera stations and the tracking of human activity implied wariness toward objects or locations resulting from their learned association with human presence rather than neophobia toward the objects themselves.

Lizards and mammals were trapped and examined for ticks from August 1992 to June 1993 in two habitat types, chaparral and woodland-grass, in northern California. Five tick species were collected from mammals (Dermacentor occidentalis, Haemaphysalis leporispalustris, Ixodes pacificus, I. spinipalpis, I. woodi), but only I. pacificus was found on lizards. Dermacentor occidentalis, I. pacificus, and I. woodi occurred in both habitats, whereas H. leporispalustris and I. spinipalpis were found only on animals trapped in chaparral. The tick species most commonly encountered on mammals was D. occidentalis in chaparral and I. pacificus in woodland-grass. Peak infestation of mammals occurred in spring for I. pacificus immatures and H. leporispalustris, summer for D. occidentalis immatures, fall through spring for I. woodi immatures, and fall through winter for I. spinipalpis. The primary aim of the study was to quantify the relative importance of the western fence lizard (Sceloporus occidentalis), which is reservoir-incompetent for Borrelia burgdorferi sensu lato (s.l.), and mammalian B.burgdorferi s.l.-reservoirs as hosts for the immature stages of I. pacificus in spring. The estimated relative utilization by I. pacificus of the western fence lizard versus mammals was 88% for larvae and 99% for nymphs in chaparral in May. When tick infestation data were corrected for a two-fold lower efficiency of field examinations for rodents than for lizards, the western fence lizard still accounted for 78% of larval and 98% of nymphal feedings. In woodland-grass, 46% of 100 I. pacificus larvae and 100% of 52 nymphs recovered from mammals or western fence lizards during May-June were collected from the lizards. However, this may represent an underestimate of the importance of the western fence lizard as a larval host in this habitat because inclement weather during the late May sampling period doubtless resulted in significantly decreased lizard activity. In conclusion, the western fence lizard was more heavily utilized by I. pacificus immatures, especially nymphs, than were rodents.

We used a large data set collected as part of a wildlife habitat study at the Blodgett Forest Research Station in the Sierra Nevada of California to assess the influence of management practices on vascular plant diversity in the mixed conifer forest. In addition to the existing data, we conducted botanical inventories in 32 plots (0.28 ha in size) from five different silvicultural regimes in 1997. Based on these inventories, understory species richness normalized to a total area sampled of 1.13 ha was significantly greater in plots under plantation (80 species) and shelterwood (77 species) management compared to plots in reserve sites (i.e., approximately 80 year with no active management, 48 species). This pattern in species richness was consistent in the larger data set. Based on 372 plots sampled between 1977 and 1996, plantations and shelterwoods routinely had the highest species richness and the reserve units routinely were the least rich. Stands under single-tree selection had species richness values closer to those of the reserve stands. The relative diversity observed in group selection plots varied from year to year. Based on the 1997 data, canopy closure and seedbed were significantly correlated to understory plant diversity. Plots that were more open and had more bare ground tended to have higher species richness. This result supports the suggestion that in addition to the total amount of biomass removed, post-harvest practices also affect plant diversity. There were considerable differences in the composition of the understory communities among silvicultural treatments. Plots under a group selection, single tree selection or reserve management regime had a greater proportion of late-seral vs. early-seral species and a lower proportion of introduced exotic species compared to plantations and shelterwoods. In this forest, more intensive management maximized species richness, but the lower intensity practices better conserved understory plants typical of late-seral stands.

Fishers ( Martes pennanti ) in the mountains of California's 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.

High biodiversity in Spanish and California woodlands is due to the intermixing of habitat types and habitat elements. Dehesa management in Spain creates a mosaic of vegetation that includes trees, shrubs, and grasslands. Maintaining this diversity requires control of invasive shrubs, but sustaining the woodlands calls for periodic management to permit an encroachment of shrubs that foster oak regeneration. Californian oak woodlands are also high in biodiversity, but have been managed far less intensively, largely for acorns and game in the pre-contact period and for livestock grazing and game in current times. Shrub invasion is slower and less common than in Spain. The impacts of livestock on oak regeneration seems to vary across California’s very heterogeneous climatic and soil conditions. Just as biodiversity supports the multifunctional dehesa economy, the possibilities of income generation from biodiversity may be crucial to the sustenance of California oak woodland ranches, reducing conversion to intensive agriculture and urbanization.

The California Wildlife Habitat Relationships (CWHR) System is a set of standardized procedures including an information system describing the management status, distribution, life history, and habitat requirements of 643 species of terrestrial vertebrates regularly occurring in California. The original CWHR Database consisted of a series of non-spatial, matrix models, including one for black-tailed deer. A series of second-generation models incorporates explicit spatial relations for use within a geographic information system. These models were designed for landscapes larger than 60 000 ha with a minimum mapping unit of 0.8 ha. As part of our development of a third-generation model applicable to landscape depictions with a minimum mapping unit of 0.06 ha, we assessed the utility of a measure of landscape composition, and an interspersion index, both based on feeding and cover habitat suitability classes found within deer home ranges. General linear model analysis indicated that the percentage of the home rang comprised by each class and the interspersion index were correlated (P < 0.05) with feeding-cover class, site, the interaction between feeding-cover class and site, and the interaction between home range type (actual or random) and site. The percentage of home ranges comprised by feeding-cover class and the level of interspersion within home ranges differed significantly by suitability class. We detected differences between actual deer home ranges and random home ranges of similar size only within the site that had significant separation in the composition of classes and the interspersion of classes. This suggests that landscape representations resulting in classes with similar composition levels and similar levels of interspersion at the scale of the animal's home range may hinder the assessment of habitat use within home ranges by promoting Type II errors. We demonstrated that organism-centered specifications for extent and grain can be defined from a generic structural representation of the landscape using functional-based models. Spatial extent was defined using the adaptive kernel home range estimator. Within this extent, habitat suitability classed based on feeding and cover produced the grain size for black-tailed deer (mean 0.44 ha, range 0.06–7.79 ha). Furthermore, this approach portrayed the low feeding-high cover matrix class exerting the dominant influence within home ranges. Thus, we suggest measures of landscape composition and interspersion may be useful for characterizing landscapes when assessing habitat use by deer. They may also be of value to natural resource managers attempting to predict the response of deer to proposed changes in land use.

We used radiotracking and other observations to describe nocturnal movement patterns of mountain lions ( Felis concolor ) during six different behaviors and attempted to estimate behavior rates by inference from such patterns. When hunting, mountain lions apparently stalked or sat in ambush for periods averaging 0.7 h and then moved a mean distance of 1.4 km (over 1.2 h) to another area; this pattern repeated about six times on nights when no prey was killed. When a mammal was killed, this pattern was suspended until the carcass was consumed (4–6 h for a small mammal, 2–5 days for a large mammal). When feeding on a large mammal, mountain lions minimized spoilage and loss to scavengers by dragging the kill 0–80 m to a cache site, burying the carcass under leaves and debris during the daytime, and feeding only at night. Mountain lions increased the risk of loss to scavengers by locating diurnal rest sites up to 4.2 km ( X = 400 m, SD = 787) from the carcass. Mating associations lasted 2–5 days, during which mountain lions traveled little, vocalized frequently, and apparently did not feed. Mothers of neonates hunted from dusk to midnight and then returned to the den; mothers spent increasing amounts of time at greater distances from the den during the first 8 weeks after giving birth. Dens were located in nearly impenetrable vegetation and den sites lacked feces, prey remains, or modifications of the site. On average, an adult mountain lion killed ca. 48 large and 58 small mammals/year and fed for an average of 2.9 days ( SD = 1.1) on a single large mammal. Although movement patterns differed markedly among behaviors, discriminant functions failed to accurately predict behavior from movement patterns.

California supports one of the greatest diversities of terrestrial wildlife of any state. However, many wildlife species have been lost or have become imperiled since the mid-1800s. Much of this biodiversity loss has been due to habitat loss caused by the conversion of wildlands to agriculture, facilitated by numerous water projects. Although certain agricultural practices can benefit wildlife, continued population growth and urban sprawl are consuming much of California's agricultural land, threatening even these benefits.

Anticoagulant rodenticide (AR) poisoning has emerged as a significant concern for conservation and management of non-target wildlife. The purpose for these toxicants is to suppress pest populations in agricultural or urban settings. The potential of direct and indirect exposures and illicit use of ARs on public and community forest lands have recently raised concern for fishers (Martes pennanti), a candidate for listing under the federal Endangered Species Act in the Pacific states. In an investigation of threats to fisher population persistence in the two isolated California populations, we investigate the magnitude of this previously undocumented threat to fishers, we tested 58 carcasses for the presence and quantification of ARs, conducted spatial analysis of exposed fishers in an effort to identify potential point sources of AR, and identified fishers that died directly due to AR poisoning. We found 46 of 58 (79%) fishers exposed to an AR with 96% of those individuals having been exposed to one or more second-generation AR compounds. No spatial clustering of AR exposure was detected and the spatial distribution of exposure suggests that AR contamination is widespread within the fisher's range in California, which encompasses mostly public forest and park lands Additionally, we diagnosed four fisher deaths, including a lactating female, that were directly attributed to AR toxicosis and documented the first neonatal or milk transfer of an AR to an altricial fisher kit. These ARs, which some are acutely toxic, pose both a direct mortality or fitness risk to fishers, and a significant indirect risk to these isolated populations. Future research should be directed towards investigating risks to prey populations fishers are dependent on, exposure in other rare forest carnivores, and potential AR point sources such as illegal marijuana cultivation in the range of fishers on California public lands.

The human desire to observe wild animals without disturbing them goes back at least to hunter-gatherers who constructed blinds. Our ability to do so was greatly enhanced with the development of photography and other, even more recent, innovations such as small, portable batteries, electric lights, and digital equipment. These technologies allow us to make undisturbed observations on a wide variety of wildlife, in a wide variety of habitats, at all hours, and under the most challenging of conditions. Our early ancestors were motivated by a desire for animal products. Today, desires for undisturbed observations of wildlife range from recreation and an aesthetic appreciation of nature to increasing our scientific understanding of animal populations and their relationship to their environment.

This paper describes an effort to map the habitat for the Eastern Tehama Deer Herd located in Northern California. The range of this herd encompasses almost 600,000 hectares (1.5 million acres). Knowledge of the spatial distribution of suitable habitat is prerequisite to managing the deer herd. Remote sensing and GIS are appropriate tools for such an assessment. Remotely sensed data were used to map vegetation/land cover. These data along with elevation, aspect, slope, juxtaposition, and various buffer zones were input into a GIS and a model was used to produce a map of habitat suitability. The accuracy of the vegetation/land cover map was assessed and methods for validating the habitat suitability map are presented.

We developed 22 new microsatellite loci for the fisher (Martes pennanti), a North American mesocarnivore. The loci were developed with samples from the southern Sierra Nevada Mountains in California, and were screened with samples from this population and four other populations. We observed a range of six to 21 polymorphic loci per population, with the Sierra Nevada population exhibiting markedly lower levels of variation compared to the other four.

Population methods. Introduction to the methods session. Data-based selection of an appropriate biological model: the key to modern data analysis. Population modelling. Trends in applied ecological modelling. Wolf recovery for Yellowstone National Park: a simulation model. Threatened populations. Research on threatened populations. The use of morphologic and molecular techniques to estimate genetic variability and relationships of small populations. Overabundant populations. Values, problems, and methodologies in managing overabundant wildlife populations: an overview. Contraception as a tool for managing feral horse populations in the western United States. Reptile and amphibian populations. The management of amphibian and reptile populations: species priorities and methodological and theoretical constraints. The use of automated data-acquisition techniques in monitoring amphibian and reptile populations. Passerine bird populations. Population models for passerine birds: structure, parameterization, and analysis. Relationships between bird density, vegetation characteristics, and grasshopper density in mixed-grass prairie of western North Dakota. Seabird populations. Seabirds: management problems and research opportunities. Point-source and non-point-source problems affecting seabird populations. Waterfowl populations. World waterfowl populations: status and dynamics. Reproductive success and population increase of black-bellied whistling ducks (Dendrocygna autumnalis) in newly placed artificial nests in a tropical freshwater marsh. Game bird populations. Long-term perspectives of upland game bird research in North America. Conservation through wise-use hunting? Raptor populations. Studies of Raptor populations: contributions to theory and conservation. Captive management for the long term survival of the California Condor. Small mammal populations. Dynamics of small mammal populations: a review. Effects of habitat patchinesson population dynamics: a modelling approach. Furbearer populations. A review of population dynamics of furbearers. Computer simulation of furbearer population dynamics. Large herbivore populations. Concepts of large herbivore populations dynamics. Genetic perspectives in wildlife management: the case of large herbivores. Marine mammal populations. Determining population status and the use of biological indices in the management of marine mammals. Status of dolphin stocks in the eastern tropical Pacific. Large carnivore populations. Large carnivore ecology: from where do we come and to where shall we go? Mark-recapture density estimation for animals with large home ranges. Index.

Coyotes (Canis latrans) are a major predator of domestic sheep (Ovis aries) grazed on open range, but studies have not examined how coyote movement patterns change in relation to this temporally intermittent and spatially clumped food resource. Using 8 resident coyotes in the Sagehen Creek watershed, Nevada County, California, we found that coyote core areas (64% adaptive kernal estimator) overlapped more while sheep were in the basin, that at least 1 resident animal followed the sheep into other animals' core areas, and that coyotes did not avoid each other in areas where sheep were concentrated. We conclude that under the conditions of our study, territoriality in coyotes does not limit coyote access to sheep. Conclusions drawn by studies of coyotes not influenced by sheep may be spurious if inferences are made to sheep-influenced populations.

We examined the diets of reintroduced tule elk (Cervus elaphus nannodes Merriam) and resident Columbian black-tailed deer (Odocoileus hemionus columbianus Richardson) inhabiting the coastal prairie-scrub mosaic of Tomales Point, the northernmost portion of the Point Reyes Peninsula, Calif., during 1979-81. The elk diet differed between years whereas the deer diet did not. The pattern of seasonal quality of elk and deer diets, as measured by fecal nitrogen (FN) was similar between species and years. This was achieved although botanical composition differed between herbivores in some seasons. Dietary overlap was lowest in the wet winter months when fecal nitrogen was highest and vegetative standing crop was lowest. Conversely, dietary overlap was highest in the dry summer months when fecal nitrogen was lowest and vegetative standing crop highest. Both herbivore species showed selection and avoidance of certain plant species in June of both years. These findings are compared to other cervid-habitat systems.

We describe resting sites used by 9 (4F:5M) radio-collared marten (Martes americana). Heights and diameters of a subsample of snags, stumps, and logs used as resting sites were measured and compared with values estimated from 80 control plots, and separately with values estimated from plots placed at 138 known marten locations. Snags, stumps, logs, and tree canopy made up 74% of 155 marten resting sites found during the study. Resting sites in snags, stumps, and logs were selected by marten and live trees were avoided. Snags, stumps, and logs used for resting sites were significantly larger than those generally available to marten. Stumps were used more in summer than winter whereas snag and log dens were used more in winter than summer. Twenty-four resting sites (16%) were re-used by marten 48 times. Preserving large snags and naturally occurring logs, and leaving cull logs and high stumps after timber harvest should benefit marten. Marten (Martes americana) occupy a variety of resting sites, including enclosed dens and exposed perches. Examination of marten rest site selection can provide managers with information on the importance of specific habitat features to this species. We found 424 marten resting sites described in the North American literature. Half (52So) of the 194 resting sites reported used in winter were in logs, stumps, or other coarse woody debris (Marshall 1951; Burnett 1981; Steventon and Major 1982; Hargis and McCullough 1984; Bateman 1986; Spencer 1987; Buskirk et al. 1989). Others were found in tree canopy (15%), grass nests, ground burrows, or features of human habitations. Half (51%) of the 142 summer resting sites reported were in snags, logs, and slash piles. Other summer resting sites were found in tree canopy (40%), dwarf mistletoe (Arceuthobium sp.) brooms, rock outcrops, willows (Salix sp.), and sedges (Campbell 1977; Masters 1980; Simon 1980; Steventon and Major 1982; Spencer 1987). Three studies did not report season of use. In these, 33 resting sites were found in stumps and logs, 34 in tree canopy, 18 in ground burrows, and 3 in grass nests (Mech and Rogers 1977; Buskirk 1984; Wynne and Sherburne 1984). The objective of this 24 mo study was to further document the patterns of resting site use by marten, including instances of repeated use of resting sites based on a sample of 155 individual sites. Additionally, we evaluated the degree of preference exhibited by marten for snags, stumps, logs, and live trees as resting sites.

From 1967 to 1970, an extensive study was made of the life history and ecology of the feral hog (Sus scroja L.) inhabiting oak woodland in the Sierra foothills. A detailed description of the feral hog included chromosome number, size, conformation, skull characteristics, dentition, tusk development, coat color, communication, social structure, and behavioral patterns. Home ranges of boars and sows were estimated to be 50 and 10 km2, respectively; hogs were capable of homing at least 15 km. Acorns were the most important food item, but green grass and forbs, wild oats, berries, bulbs, roots, insects, and carrion were also eaten. Hogs grazing irrigated pastures during the summer consumed more green forage and crude protein and exhibited significantly greater growth rates than hogs without access to pastures. Pen-raised feral hogs were found capable of growth equal to domestic swine, but typical free-ranging hogs exhibited growth rates of only half their potential. Sows bred continuously after the age of 6 to 10 months, averaging two litters per year and 5.6 young per litter at birth. Sows with access to irrigated pastures produced 20 percent more fetuses than those without access. From birth to 6 months of age, piglets sustained a 70 to 90 percent mortality. Losses were due to accidents, predation and starvation. Insufficient milk resulting from low levels of protein in the sows’ diets was a major underlying cause of piglet losses. Hunting was the major cause of adult mortality. Tooth abscesses and related infections were the most important natural causes of adult mortality. Population density ranged from five to eight hogs per square kilometer on the 130-km2 study area. Although the annual kill averaged 21 percent, the population increased 10 percent per year from 1966 to 1970. Young hogs made up nearly half and yearlings made up nearly a quarter of the fall population in 1969. The proposed management program aims to economically control feral hog populations on private lands by paid recreational hunting, thus providing income for the landowner and recreation for the public.

Pine martens ( Martes americana ) consume a variety of food types annually but seasonal foraging is restricted to a subset of available prey. Winter foods include chickarees ( Tamiasciurus douglasii ), voles ( Microtus spp.), snowshoe hares ( Lepus americanus ), and flying squirrels ( Glaucomys sabrinus ), whereas ground-dwelling sciurids ( Spermophilus spp. and Eutamias spp.) comprise the bulk of the diet during the remainder of the year. Activity also is variable by season, with martens foraging at night during winter and by day during summer. Seasonal marten activity does not appear associated with optimal ambient temperature but instead appears synchronized with the activity of prey.

Antler anomalies were evident in tule elk (Cervus elaphus nannodes) within 1 yr of reintroduction to Point Reyes, California (USA). These anomalies are consistent with previously described mineral deficiency-induced anomalies in cervids. The elk were judged deficient in copper. Low levels of copper in soils and vegetation at the release site, exacerbated by possible protein deficiency due to poor range conditions, are postulated as likely causes of the antler anomalies.

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.

Foraging habits and relative abundances of 12 birds comprising the insect-gleaning guild in a Sierran mixed-conifer forest were studied during two breeding seasons to determine: (1) foraging habitat preferences, (2) the extent to which species differ in their use of various components of the foraging niche, (3) patterns of relative abundance vs. niche breadth, and (4) differences between resident and migrant species. Comparisons of proportional availability and bird use of foliage height classes and tree species showed that tree species and, to a lesser extent, heights were used selectively by the guild. Incense-cedar (Calocedrus decurrens) was consistently avoided by all species; other tree species were generally used in a complementary manner by different birds. Of four measured components of foraging niche, the use of foraging site (consisting of air or tree part) showed the greatest difference between species, followed by tree species, foraging techniques, and foraging height. We found no correlation between niche breadth and species abundance for all guild members; however, a significant positive correlation existed for the five resident species. Resident and migrant species groups showed few fundamental differences in foraging patterns, except that migrants tended to use a greater proportion of deciduous foliage than residents. Our results suggest that to provide for this guild, land managers should maintain natural levels of tree species diversity in the mixed-conifer forest type. Many studies have shown that syntopic insectivorous birds differ in their methods of foraging. In forested habitats, birds tend to use different foraging techniques, foraging sites, tree species, and heights. The relative importance of these foraging niche components in distinguishing species has received less attention. Differences in importance of niche components reported in previous studies may reflect either real differences that exist in different habitats and geographic areas (Balda 1969), or incomplete analysis of all potentially relevant factors (Holmes and Robinson 1981). In particular, the importance of differential plant species use has not been fully appreciated (Holmes and Robinson 1981). Additional information is needed before sound generalizations can be made regarding patterns of differentiation among insect-gleaning birds. In managed forests, plant species composition and vegetation structure may be altered by logging, other silvicultural activities, and disruption of natural fire regimes (Kilgore 1971, Franzreb and Ohmart 1978, Szaro and Balda 1979). Identification of habitat preferences of forest birds can suggest recommendations to mitigate impacts of manipulation. The mixed-conifer forest of the Sierra Nevada, California, supports a large number of arboreal insectivorous birds (Verner and Boss 1980). We studied foraging substrate preferences, foraging behaviors and relative abundances of the 12 most common members of an insect-gleaning guild. We sought to: (1) compare the guild's use of tree species and vertical foliage layers with the availabilities of these habitat components; (2) describe and compare foraging sites and techniques used by each species; (3) evaluate the relative importances of foraging heights, tree species use, foraging sites, and foraging techniques in differentiating species ecologically; (4) determine if resident and migrant species differed in their foraging and abundance patterns; and (5) suggest management recommendations to mitigate the effects of habitat manipulation on members of the insect-gleaning guild.

Growth rates in 2 re-established populations of tule elk (Cervus elaphus nannodes) were followed 6 and 7 years beyond the time of introduction. The elk population at Grizzly Island, California, grew at the maximum potential rate, whereas that at Point Reyes, California, grew at half the theoretical potential. The lower rate of growth at Point Reyes was attributed to an initial pulse of adult mortality, low calving rates, and high subadult mortality. J. WILDL. MANAGE. 51(1):20-27 Studies of introduced ungulate populations immediately following release are limited. The paucity of such information has led to experimental manipulation of populations to duplicate growth from low numbers (McCullough 1979, 1982). We report growth rates for 2 reintroductions of tule elk at Point Reyes and Grizzly Island, California. Both areas supported tule elk, at least seasonally, in pristine times but not since the 1860's (McCullough 1969). Reintroductions of elk began in 1977. Ten adult elk (2 males and 8 females) were transported in March 1978 from San Luis National Wildlife Refuge, Merced County, to a holding pen on a 1,030ha fenced portion of Point Reyes. Nine calves (1978 cohort) were born while the animals were confined within the pen (Ray 1981). Ten adults and 7 surviving calves (4 males and 3 females) were released to the entire range in September 1978. Three adult males from the Owens Valley, Inyo County, were reintroduced in December 1981. They were sighted occasionally in January and February 1982, but subsequently disappeared, and are not considered further. Seven adult elk (4 males and 3 females) were relocated to Grizzly Island from the Tule Elk State Reserve, Tupman, Kern County in February 1977. The animals were restricted to a holding pen until released, on site, in May. A yearling female, originally from Owens Valley, was released at Grizzly Island later that year. In May 1978, an adult female from Owens ValThis content downloaded from 153.90.6.19 on Wed, 25 Jun 2014 13:23:08 PM All use subject to JSTOR Terms and Conditions J. Wildl. Manage. 51(1):1987 INTRODUCED ELK POPULATIONS * Gogan and Barrett 21 ley joined the herd. One of the original 4 adult males was moved to another release site. An adult male was poached in November 1979, and a male seriously injured in the rut was sacrificed in September 1982. In 1978, both populations numbered 17 elk. We thank W. H. Sohrweide for sharing his observations of tule elk at Grizzly Island with us. Thanks are due J. J. Aho, Jr., T. S. Biller, W. J. Pierce, and R. T. Lesko of Point Reyes Natl. Seashore and D. A. Jessup and B. E. Curtis of the Calif. Dep. Fish and Game (CDFG) for assistance and encouragement during this study. We thank D. B. Houston, R. A. Lancia, and D. R. McCullough for reviewing earlier drafts of this manuscript, and L. M. Merkle for typing the final and earlier drafts. Research was funded by the Natl. Park Serv. under Contract CX 800-9-0029 and Calif. Agric. Exp. Stn. Proj. 3501-MS. The senior author was a Rob and Bessie Welder Wildl. Found. Fellow and this manuscript is Welder Wildl. Found. Contrib. 209.

The relative habitat preferences of feral hogs (Sus scrofa), blacktailed deer (Odocoileus hemionus columbianus), and cattle were assessed for 17 habitat types by sampling the distribution and abundance of fecal sign on a northern California annual range. Hogs preferred oak thickets and irrigated pastures; deer preferred brushland and oak woodland; and cattle preferred level topography and sites with relatively high herbage production including irrigated pastures, upland plains, and oak savanna-woodland. Deer and cattle used the study area during winter only, whereas the hogs were permanent residents. An association analysis indicated the greatest potential for interspeciflc competition would be between cattle and deer on foothill ridge tops and between cattle and hogs on irrigated pastures. As part of a study of the life history and ecology of the feral hog in California (Barrett 1978) a preliminary analysis was made of the habitat preferences of the three ungulates (hogs, deer, and cattle) living on the Dye Creek Ranch situated 15 km south of Red Bluff, Tehama County, California. The results were used to delineate those habitats (range sites) on which there is a potential for conflict between livestock and game preserve enterprises utilizing the same land. Information is available on the habitat preferences of deer and cattle on Sierra foothill rangelands (Leopold et al. 1951, Wagnon 1968), but little is available for feral hogs (Pine and Gerdes 1973). No studies have considered all three species simultaneously. Study Area and Methods The study area included a portion of the eastern plains of the Sacramento Valley and stretched eastward 15 km into the lower foothills of Mt. Lassen. The climate is Mediterranean with annual rainfall averaging 450-650 mm (Barbour and Major 1977). The foothills rise to 400 m above the valley floor and are dissected by east-west draiinages. Available habitats were subjectively classified on aerial photos using topographic and vegetation criteria. Topographic categories included: (I) plains of the Sacramento Valley floor, (2) flat ridge-tops between the river canyons with slopes under 10%, (3) north, and (4) south slopes of the canyons. Vegetation categories included: ( 1) irrigated pasture, (2) upland plain, (3) boulder wash, (4) south slopes of the canyons. Vegetation categories included: (I) irrigated pasture, (2) upland plain, (3) boulder wash, (4) rock-grass, (5) buckbrush, (6) oak savanna, (7) oak woodland, and (8) oak thicket (includes riparian forest). The first 3 The author is assistant professor, Department of Forestry and Resource Management, University of California, Berkeley 94720. Funds for this study were supplied by a National Science Foundation Graduate Fellowship, the Dye Creek Field Station, Union Wildlife Foundation Fund, University of California Department of Zoology, and California Agricultural Experiment Station. I thank W. Long and W.S. Keeler of the Dye Creek Ranch for instigating and supporting this study, and Drs. A.S. Leopold, M. White, H.F. Heady, L.A. Jaechel, and J. Patton, all of the University of California, for their counsel and support throughout the project. I particularly want to thank Kathy Barrett who helped in all aspects of the study. Scientific and common names follow Storer and Usinger (1963). Manuscript received May 29, 1980. vegetation categories (Fig. I) are located exclusively in the Sacramento Valley below 100 m elevation on old floodplains and terraces (U.S. Department of Agriculture 1967). The remaining five vegetation categories (Fig. 2) are found only in the foothills (Barrett 1978). A total of 17 combinations of the topographic and vegetation categories were mapped as habitat types. Mapping units varied between 50 and 200 m in width, thus were small relative to ungulate home ranges. Two resident feral hog sub-populations were recognized (Barrett 1978), and sampling was stratified accordingly into a valley edge area (2327 ha) and a foothill area ( 1562 ha). Deer and cattle utilized the study area as winter range and had free access to all habitats in both strata, with the exception that cattle were restricted by fences in irrigated pastures. North-south belt transects were positioned systematically at intervals of 0.8 km. In 1968, 448 plots (1.5 X 32 m) were sampled (0.06% sample), but only 291 plots were sampled in 1969 (0.04% sample). The proportion of plots located in each habitat type was used as an indicator of the availability of each type. Sampling of accumulated hog scats, deer pellet groups (1968 only), and cow pats in each plot was completed within 2 weeks during September each year just prior to the influx of deer and cattle. This season was selected after pilot samples indicated the density of hog scats was greatest at the end of the dry season. Most deer and cattle droppings from the previous winter also remained identifiable through the dry season. Thus the data are representative of the fecal deposition pattern for each species over a 2-year period. Data were pooled for all plots within each habitat type and compared between years and between strata. The frequency of occurrence and density of sign of each animal were calculated for each habitat type. A Chi-square test of association indicated that the frequency distributions of all types of sign were not significantly different (P

Stepwise logistic regression was used to identify factors important for habitat use by beavers (Castor canadensis) on streams. Increasing stream width and depth and decreasing gradient had the strongest positive effects on habitat use; food availability variables added little explanatory power. Some abandoned colony sites appeared to have been located on physically unsuitable habitat, whereas others appeared to be physically suitable sites abandoned due to resource depletion. The fact that few unused or uncolonized reaches were misclassified as suitable habitat suggests that suitable habitat has been saturated. Impact of beaver on woody plants was assessed for 8 forage species. Local extinction of quaking aspen (Populus tremuloides) and black cottonwood (P. trichocarpa) occurred on 4-5% of stream reaches. Willow (Salix spp.) showed good vigor despite heavy use in most reaches. J. WILDL. MANAGE. 51(4):794-799 Multivariate wildlife-habitat relationships models are often used to identify actually or potentially suitable habitat for various species, or to identify those factors that are important in habitat selection (Shugart 1981). Retzer (1955), Slough and Sadlier (1977), and Howard and Larson (1985) have used quantitative techniques to relate beaver occurrence, persistence, and density to various physical and vegetative characteristics. Wildlife managers have long been concerned with the loss of aesthetic value and impacts on stream channels due to destruction of riparian vegetation by beaver (Bump 1941, Munther 1981). Hall (1960) reported that beaver will deplete aspen in the immediate vicinity of a colony. However, there has been little quantitative documentation of the role of these animals in the loss of riparian vegetation (Kindschy 1985). Our objectives were to: (1) develop a model to identify the physical and vegetative characteristics of habitat colonized by beavers, and validate the model on a set of stream reaches not used in model development; (2) use the model results to suggest causes for colony abandonment, and evaluate whether beaver have saturated suitable habitat during the 40 years since introduction; and (3) describe the impact of beavers on woody vegetation. This research was supported by the Calif. Dep. Fish and Game and the Calif. Agric. Exp. Stn. Proj. 4326-MS. J. S. Slaymaker assisted in most of the fieldwork. M. L. Morrison, R. A. Lancia, S. H. Jenkins, and W. M. Block provided helpful criticisms of the manuscript. STUDY AREA The Truckee River Basin lies within Sierra, Nevada, Placer, and El Dorado counties, California, and Washoe County, Nevada. Our study covered the Truckee River and its tributaries from the confluence with Deer Creek downstream to Verdi, Nevada. This encompassed an area of approximately 600 km2, with 153 km of streams ranging from 1,485 to 2,750 m in elevation. Beavers were introduced into the area during 1938-46 and have since established colonies throughout the basin (P. Beier and R. H. Barrett, unpubl. data). The dominant vegetation of the area is mixed conifer forest with an overstory of white fir (Abies concolor); Jeffrey (Pinus jeffreyi), ponderosa (P. ponderosa), Washoe (P. washoensis), and lodgepole (P. contorta) pine; and a shrub component including greenleaf (Arctostaphylos patula) and whiteleaf (A. viscida) manzanita, snowbrush (Ceanothus velutinus) and squawcarpet ceanothus (C. prostratus), pale serviceberry (Amelanchier pallida), rose (Rosa spp.), and Sierra gooseberry (Ribes roezlii). The mixed conifer forest is replaced in higher elevations by a forest dominated by Shasta red fir (Abies magnifica), western white pine (P. monticola), and lodgepole pine, with squawcarpet as a dominant shrub; and in lower elevations by open stands of Jeffrey pine and an understory including big sagebrush (Artemisia tridentata), antelope bitterbrush (Purshia tridentata), and herbaceous plants. Stream banks were characterized by deciduous riparian vegetation consisting of aspen, cottonwood, willow, mountain alder (Alnus in