Rick A. Sweitzer

Testing the consistency of wildlife data types before combining them: the case of camera traps and telemetry

Wildlife data gathered by different monitoring techniques are often combined to estimate animal density. However, methods to check whether different types of data provide consistent information (i.e., can information from one data type be used to predict responses in the other?) before combining them are lacking. We used generalized linear models and generalized linear mixed-effects models to relate camera trap probabilities for marked animals to independent space use from telemetry relocations using 2 years of data for fishers (Pekania pennanti) as a case study. We evaluated (1) camera trap efficacy by estimating how camera detection probabilities are related to nearby telemetry relocations and (2) whether home range utilization density estimated from telemetry data adequately predicts camera detection probabilities, which would indicate consistency of the two data types. The number of telemetry relocations within 250 and 500 m from camera traps predicted detection probability well. For the same number of relocations, females were more likely to be detected during the first year. During the second year, all fishers were more likely to be detected during the fall/winter season. Models predicting camera detection probability and photo counts solely from telemetry utilization density had the best or nearly best Akaike Information Criterion (AIC), suggesting that telemetry and camera traps provide consistent information on space use. Given the same utilization density, males were more likely to be photo-captured due to larger home ranges and higher movement rates. Although methods that combine data types (spatially explicit capture–recapture) make simple assumptions about home range shapes, it is reasonable to conclude that in our case, camera trap data do reflect space use in a manner consistent with telemetry data. However, differences between the 2 years of data suggest that camera efficacy is not fully consistent across ecological conditions and make the case for integrating other sources of space-use data.

Canine Distemper in an Isolated Population of Fishers (Martes pennanti) from California

Four fishers (Martes pennanti) from an insular population in the southern Sierra Nevada Mountains, California, USA died as a consequence of an infection with canine distemper virus (CDV) in 2009. Three fishers were found in close temporal and spatial relationship; the fourth fisher died 4 mo later at a 70 km distance from the initial group. Gross lesions were restricted to hyperkeratosis of periocular skin and ulcera-tion of footpads. All animals had necrotizing bronchitis and bronchiolitis with syncytia and intracytoplasmic inclusion bodies. Inclusion bodies were abundant in the epithelia of urinary bladder and epididymis but were infrequent in the renal pelvis and the female genital epithelia. No histopathologic or immu-nohistochemical evidence for virus spread to the central nervous system was found. One fisher had encephalitis caused by Sarcocystis neurona and another had severe head trauma as a consequence of predation. The H gene nucleo-tide sequence of the virus isolates from the first three fishers was identical and was 99.6% identical to the isolate from the fourth fisher. Phylogenetically, the isolates clustered with other North American isolates separate from classical European wildlife lineage strains. These data suggest that the European wildlife lineage might consist of two separate subgroups that are genetically distinct and endemic in different geographic regions. The source of infection as well as pertinent transmission routes remained unclear. This is the first report of CDV in fishers and underscores the significance of CDV as a pathogen of management concern.

Patterns of Natural and Human-Caused Mortality Factors of a Rare Forest Carnivore, the Fisher (Pekania pennanti) in California

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.

Reproduction, abundance, and population growth for a fisher (Pekania pennanti) population in the Sierra National Forest, California

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 (&lgr;). 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/km2. 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 &lgr; 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 &lgr; 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 &lgr; 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.

An evaluation of a weaning index for wild fishers (Pekania [Martes] pennanti) in California

Abstract Conservation concern for fishers (Pekania [Martes] pennanti) in the Pacific states has highlighted a need to develop cost-effective methods of monitoring reproduction in extant and reintroduced fisher populations. We evaluated the efficacy of nipple size as a predictive index of weaning success for females with known reproductive histories from 3 study areas in California. We captured and radiocollared 91 female fishers on 146 occasions between 2004 and 2011 and measured the width and height of all 4 nipples and quantified reproductive status via radiotelemetry. We classified each radiomarked female into 1 of 3 reproductive classes (nonbreeders, attempted breeders, and current breeders) based on our telemetry observations during the den season prior to capture. We used a modified random forests (RF) procedure to account for repeated measures of individual females sampled in multiple years. Our modified RF procedure correctly classified reproductive class for 130 (89%) and 131 (90%) of our 146 observations using raw and weighted vote totals, respectively. We calculated Cohens kappa of 0.80 and 0.81 using raw and weighted vote totals, respectively, indicating strong model performance. We conclude that nipple sizes of female fishers measured during a livetrapping effort can be used as a cost-effective index of the weaning rates of adult female fishers.

CLIMATE AND HABITAT INFLUENCE PREVALENCE OF MENINGEAL WORM INFECTION IN NORTH DAKOTA, USA.

Abstract The meningeal worm (Parelaphostrongylus tenuis) is a parasite of white-tailed deer (Odocoileus virginianus) and is also a significant pathogen of moose (Alces alces) and other ungulates. Changes in climate or habitat may facilitate range expansion or increase the prevalence of meningeal worm infection in white-tailed deer, resulting in increased exposure to susceptible ungulates. We examined 3,730 white-tailed deer during 2002–05 to determine the prevalence and range of meningeal worm infection in North Dakota, US, and investigated whether these had changed since earlier surveys. We used multiple logistic regression to model potential effects of habitat and climate on prevalence in white-tailed deer. We also examined how habitat influences intermediate hosts by comparing gastropod abundance and microclimate among habitat types. Prevalence in deer was 14% statewide, and prevalence and geographic range had increased since the early 1990s. Natural woodlands provided the best habitat for intermediate hosts, and increases in prevalence of infection in deer may be due to recent patterns in growing-season precipitation. This study has redefined the geographic distribution of meningeal worm infection and increased understanding of how climate and habitat influence the prevalence and distribution of this parasite.

Survival of fishers in the southern Sierra Nevada region of California

Fishers in the western United States were recently proposed for listing under the U.S. Endangered Species Act because of concerns for loss of suitable habitat and evidence of a diversity of mortality risks that reduce survival. One of 2 remnant populations of fishers in California is in the southern Sierra Nevada region, where we studied them at 2 research sites in the Sierra National Forest. Our objectives were to evaluate whether survival was lower for male fishers and dispersal-aged individuals or if survival varied seasonally. We captured and monitored 232 radiocollared fishers from March 2007 to March 2014 and used model analyses to identify important predictors of survival. Fifty-two percent (n = 120) of the radiocollared fishers died, and survival varied by sex and season, but not by age or between study sites. There was no evidence that dispersal-aged fishers experienced lower survival than older fishers. Annual survival trended lower for male (0.62 [95% CI 0.54–0.70]) compared to female fishers (0.72 [95% CI 0.67–0.78]), was lowest in the spring to mid-summer season (0.83 [95% CI 0.78–0.87]), and highest in late fall and winter (0.92 [95% CI 0.89–0.94]). Lower survival among male fishers appeared linked to males moving over large areas to locate mates, while lower survival for females was potentially related to high energetic cost of reproduction. It was possible but unknown if lower survival among all fishers in spring was linked to secondary exposure to toxicants dispersed around illicit marijuana grow sites. Six-month survival of juvenile fishers was 0.85 for females and 0.79 for males, but lower at 0.62 for females and 0.57 for males when adjusted for deaths before late September. Annual survival among adult female fishers was 20% lower than 0.90, a value that prior modeling suggested was required for population expansion in the overall southern Sierra Nevada. Survival data from our study imply a greater challenge for maintaining self-sustaining fisher populations in the southern Sierra Nevada region, and resource managers are working to mitigate several of the human-associated factors that limit population growth.