Feral pigs (Sus scrofa) are an exotic ungulate which have been widely introduced worldwide with multiple ecosystem and economic consequences. The author conducted a semi-comprehensive literature review directed at identifying the current state of knowledge related to the effects of feral pigs on island and mainland plant and animal communities. Also, the author describes the situation in California where feral pigs that were introduced in the late 1700s are now widespread due to hunting-related introductions and natural range extensions. Feral pigs on predator-free oceanic islands are a serious conservation problem because they attain high densities and have contributed to near-extinctions and extinctions of multiple endemic plants and vertebrates. In mainland ecosystems, however, feral pigs can have both positive and negative effects depending on the local circumstances. Rooting, for example, can have both positive and negative effects on growth and survival of some trees, soils and soil processes, and the distribution of native and exotic grasses. In general, however, the negative effects of rooting by feral pigs are amplified when population densities are high. Feral pigs may compete with native species for limited resources, but there are limited data relevant to this hypothesis. Based on observations of small amounts of animal matter in their diets, feral pigs eat terrestrial vertebrates and eggs of ground nesting birds, but the importance of predation by feral pigs on native vertebrates is poorly known. Feral pigs also may have important indirect effects in mainland ecosystems by providing a new prey base for native predators which may then increase. In areas of Europe with extant wolf (Canis lupus) populations, wild boar (Sus scrofa) are an important prey species which may be facilitating numerical and geographic recoveries of wolves. Because wild boar are important prey for endangered Amur tigers (Panthera tigris), they are considered important for recovering tiger populations. In Australia, feral pigs are potentially important prey for dingoes (Canis familiaris dingo); whereas, in the United States, endangered Florida panthers (Felis concolor coryi) consumed 23% to 59% feral pigs, and mountain lions (Felis concolor) in Texas and California consumed 5% to 38% feral pigs. Research needs for feral pigs include quantitatively assessing: 1) how acorn foraging by feral pigs limits or influences regeneration of oaks (Quercus sp.); 2) the competitive effects of feral pigs on native species; 3) whether direct predation by feral pigs suppresses small vertebrate populations; and 4) how the availability of feral pigs as prey influences native predator populations.

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.

In 1994 and 1995, 233 different wild pigs were captured during population research at seven research sites focused primarily in the coastal regions of central and northern California. Mark-resight data and information on wild pig movements were used to assess wild pig population densities at those sites. Population densities ranged from 1.01 wild pigs/km2 in Mendocino County in 1994 to 3.32 wild pigs/km2 in Santa Clara County in 1995. Comparisons of population densities between years at three research sites suggested that wild pig populations increased in 1995 in response to favorable forage conditions after the wet fall and winter of 1994-95. Serum samples collected from 462 wild pigs at 28 different sites were screened for exposure to brucellosis and pseudorabies. Preliminary results were that seropositive results for brucellosis were noted at only three sites, whereas no animals were confirmed seropositive for pseudorabies. Although analyses of these two diseases are continuing, test results for trichinellosis, toxoplasmosis, and sylvatic plague reinforce previous warnings to hunters and consumers that sanitary handling and cooking of wild swine meat are warranted.

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.

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.