Spilogale Gracilis Research Articles

Navigating cross-reactivity and host species effects in a serological assay: A case study of the microscopic agglutination test for Leptospira serology.

Serology (the detection of antibodies formed by the host against an infecting pathogen) is frequently used to assess current infections and past exposure to specific pathogens. However, the presence of cross-reactivity among host antibodies in serological data makes it challenging to interpret the patterns and draw reliable conclusions about the infecting pathogen or strain. In our study, we use microscopic agglutination test (MAT) serological data from three host species [California sea lion (Zalophus californianus), island fox (Urocyon littoralis), and island spotted skunk (Spilogale gracilis)] with confirmed infections to assess differences in cross-reactivity by host species and diagnostic laboratory. All host species are known to be infected with the same serovar of Leptospira interrogans. We find that absolute and relative antibody titer magnitudes vary systematically across host species and diagnostic laboratories. Despite being infected by the same Leptospira serovar, three host species exhibit different cross-reactivity profiles to a 5-serovar diagnostic panel. We also observe that the cross-reactive antibody titer against a non-infecting serovar can remain detectable after the antibody titer against the infecting serovar declines below detectable levels. Cross-reactivity in serological data makes interpretation difficult and can lead to common pitfalls. Our results show that the highest antibody titer is not a reliable indicator of infecting serovar and highlight an intriguing role of host species in shaping reactivity patterns. On the other side, seronegativity against a given serovar does not rule out that serovar as the cause of infection. We show that titer magnitudes can be influenced by both host species and diagnostic laboratory, indicating that efforts to interpret absolute titers (e.g., as indicators of recent infection) must be calibrated to the system under study. Thus, we implore scientists and health officials using serological data for surveillance to interpret the data with caution.

Western spotted skunk spatial ecology in the temperate rainforests of the Pacific Northwest

AbstractA major threat to small mammalian carnivore populations is human‐induced land use change, but conservation and management are inhibited by limited knowledge about their ecology and natural history. To fill a key knowledge gap of the western spotted skunk (Spilogale gracilis), we investigated their spatial ecology at the landscape and home range scale in the temperate rainforests of the Oregon Cascades during 2017–2019. For the landscape scale analysis, we used detections of western spotted skunks at 112 baited camera traps and fitted a dynamic occupancy model to investigate spatial distribution and drivers of inter‐seasonal and inter‐annual changes in occupancy. Concurrently, we radio‐collared 25 spotted skunks (9 female, 16 male) and collected 1583 relocations. Using continuous‐time movement models, we estimated large home range sizes for both male and female spotted skunks, relative to their body mass, and highly overlapping home ranges that indicated a lack of territoriality. Using these home ranges, we fitted a resource selection function using environmental covariates that we assigned to various hypotheses such as resources, predator avoidance, thermal tolerance, and disturbance. Overall, western spotted skunks were widely distributed across our study area (seasonal occupancy up to 63.7 ± 5.3%) and highly detectable (weekly detection probability = 41.2%). At both spatial scales, spotted skunks selected wetter areas and local valleys, which we attributed to areas with more food resources. At the home range scale, spotted skunks selected locations with lower predation risk and areas surrounded by more previously logged forests. In this montane environment, inter‐seasonal contractions in the spatial distributions of spotted skunks were strongly driven by their response to cold temperature and accumulated snow. This was especially evident when seasonal occupancy declined significantly following a severe heavy snow event in February 2019. Given that there is little information available on the natural history of the western spotted skunk, these results provide essential information about their ecology to focus future monitoring efforts and may help identify potential threats (e.g., forest management, severe snow events, or wildfires) to this species.

The gut microbiomes of Channel Island foxes and island spotted skunks exhibit fine-scale differentiation across host species and island populations.

California's Channel Islands are home to two endemic mammalian carnivores: island foxes (Urocyon littoralis) and island spotted skunks (Spilogale gracilis amphiala). Although it is rare for two insular terrestrial carnivores to coexist, these known competitors persist on both Santa Cruz Island and Santa Rosa Island. We hypothesized that examination of their gut microbial communities would provide insight into the factors that enable this coexistence, as microbial symbionts often reflect host evolutionary history and contemporary ecology. Using rectal swabs collected from island foxes and island spotted skunks sampled across both islands, we generated 16S rRNA amplicon sequencing data to characterize their gut microbiomes. While island foxes and island spotted skunks both harbored the core mammalian microbiome, host species explained the largest proportion of variation in the dataset. We further identified intraspecific variation between island populations, with greater differentiation observed between more specialist island spotted skunk populations compared to more generalist island fox populations. This pattern may reflect differences in resource utilization following fine-scale niche differentiation. It may further reflect evolutionary differences regarding the timing of intraspecific separation. Considered together, this study contributes to the growing catalog of wildlife microbiome studies, with important implications for understanding how eco-evolutionary processes enable the coexistence of terrestrial carnivores-and their microbiomes-in island environments.

Diversity of Babesia spp. in skunks from selected states in the United States of America.

Babesia species are intraerythrocytic protozoan parasites that infect a variety of hosts. The goal of this study was to evaluate the piroplasm species present in skunks in various states in the United States and determine whether there was any geographic variation. Spleen, whole blood, or blood on filter paper were received from Pennsylvania, Kentucky, North Carolina, South Carolina, Georgia, Missouri, Louisiana, Texas, Kansas, and California, and were tested for Babesia sp. We tested four species of skunks including striped skunk (Mephitis mephitis, n=72), eastern spotted skunk (Spilogale putorius, n=28), western spotted skunk (Spilogale gracilis, n=15), and hog-nosed skunk (Conepatus leuconotus, n=11). A PCR assay targeting the 18S rRNA region and cox1 region were used to determine if skunks were infected with piroplasms and for phylogenetic analyses. A total of 48.4% (61/126) of skunks tested positive for a Babesia species. Both the 18S and cox1 analysis supported a skunk-specific Babesia microti-like sp. of carnivores as well as a species in the B. microti complex that is phylogenetically unique from both B. microti of humans and the B. microti-like sp. of carnivores. In the 18S analysis, there was a third species of Babesia in hog-nosed skunks in the western piroplasm group. This study shows that at least three species of piroplasms occur in skunk species in the United States and further highlights the importance of phylogenetic analyses and the use of multiple gene targets when studying piroplasms.

Prevalence of Trypanosoma cruzi, the Etiologic Agent of Chagas Disease, Infection in Texas Skunks (Mammalia: Mephitidae).

Background: Chagas disease is one of the world's most neglected tropical diseases, infecting over six million people across the Americas. The hemoparasite Trypanosoma cruzi is the etiological agent for the disease, circulating in domestic, peridomestic, and sylvatic transmission cycles that are maintained by triatomine vectors and a diversity of wild and synanthropic hosts. Public health and wildlife management interventions targeting the interruption of T. cruzi transmission rely on an understanding of the dynamics driving the ecology of this zoonotic pathogen. One wildlife host that purportedly plays a role in the transmission of Chagas disease within the southern United States is the striped skunk (Mephitis mephitis), although infection prevalence in this species is poorly understood. Materials and Methods: To this end, we conducted a PCR-based surveillance of T. cruzi in 235 wild skunks, representing 4 species, across 76 counties and 10 ecoregions in Texas, United States, along with an evaluation of risk factors associated with the infection. Results: We recovered an overall T. cruzi prevalence of 17.9% for all mephitid taxa aggregated, ranging between 6.7% for plains spotted skunks (Spilogale putorius interrupta) and 42.9% for western spotted skunks (Spilogale gracilis). We report the first cases of T. cruzi infection in plains spotted and American hog-nosed skunks (Conepatus leuconotus), of important note for conservation medicine since populations of both species are declining within Texas. Although not statistically significant, we also detected trends for juveniles to exhibit greater infection risk than adults and for differential sex biases in T. cruzi prevalence between taxa, which align with variations in species-specific seasonal activity patterns. No geographic or taxonomic risk factors were identified. Conclusion: Our study contributed key data for population viability analyses and epidemiologic models in addition to providing a baseline for future T. cruzi surveillance among skunks and other wildlife species.

Multi‐locus DNA metabarcoding reveals seasonality of foraging ecology of western spotted skunks in the Pacific Northwest

AbstractThere are increasing concerns about the declining population trends of small mammalian carnivores around the world. Their conservation and management are often challenging due to limited knowledge about their ecology and natural history. To address one of these deficiencies for western spotted skunks (Spilogale gracilis), we investigated their diet in the Oregon Cascades of the Pacific Northwest during 2017–2019. We collected 130 spotted skunk scats opportunistically and with detection dog teams and identified prey items using DNA metabarcoding and mechanical sorting. Western spotted skunk diet consisted of invertebrates, such as wasps, millipedes, and gastropods; vertebrates, such as small mammals, amphibians, and birds; and plants, such as Gaultheria, Rubus, and Vaccinium. Diet also consisted of items, such as black‐tailed deer, that were likely scavenged. Comparison in diet by season revealed that spotted skunks consumed more insects during the dry season (June–August), particularly wasps (75% of scats in the dry season), and marginally more mammals during the wet season (September–May). We observed a similar diet in areas with no record of human disturbance and areas with a history of logging at most spatial scales, but scats collected in areas with older forest within a skunk's home range (1‐km buffer) were more likely to contain insects. Western spotted skunks provide food web linkages between aquatic, terrestrial, and arboreal systems and serve functional roles of seed dispersal and scavenging. Due to their diverse diet and prey switching, western spotted skunks may dampen the effects of irruptions of prey, such as wasps, during dry springs and summers. By studying the natural history of western spotted skunks in the Pacific Northwest forests, while they are still abundant, we provide key information necessary to achieve the conservation goal of keeping this common species common.

BARRED OWL PREDATION OF WESTERN SPOTTED SKUNKS

The potential for trophic cascades triggered by recent range expansion of the Barred Owl (Strix varia) to the Pacific Northwest has caused concern among conservationists and managers. Barred Owl predation of small forest carnivores is a particular concern because these carnivores typically have low population growth rates relative to their body size owing to long interbirth intervals, which may result in sensitivity to increased mortality. The Western Spotted Skunk (Spilogale gracilis) is a common small carnivore in forests of the Pacific Northwest that may be a prey item for Barred Owls, and previous research suggests that avian predation can be a primary cause of mortality for congeneric spotted skunks (Spilogale spp.). We report a confirmed predation event of a Western Spotted Skunk by a Barred Owl and 3 additional predation events that we suspect were due to Barred Owls based on circumstantial evidence. During a Western Spotted Skunk research study, we recovered the radio collar of an adult male skunk from the top of a tall snag and located intestines and avian feces at the base of this snag. DNA metabarcoding revealed that the avian feces contained Western Spotted Skunk and Barred Owl DNA. Barred Owls are a novel predator of the Western Spotted Skunk in forests of the Pacific Northwest and may have both direct and indirect negative impacts on Western Spotted Skunk populations.

Interspecific Asymmetries in Behavioral Plasticity Drive Seasonal Patterns of Temporal Niche Partitioning in an Island Carnivore Community.

Animals vary considerably in the amount of behavioral plasticity they exhibit in daily activity timing and temporal niche switching. It is not well understood how environmental factors drive changes in temporal activity or how interspecific differences in the plasticity of activity timing ultimately manifest in free-living animals. Here, we investigated the temporal structure and organization of activity patterns of two insular mammalian carnivores living in sympatry, the island fox (Urocyon littoralis) and island spotted skunk (Spilogale gracilis amphiala). Using collar-mounted accelerometers, we assessed the plasticity of behavioral activity rhythms in foxes and skunks by investigating how environmental factors drive the distribution of locomotor activity across the day and year, and subsequently examined the dynamics of temporal niche overlap between the two species. We documented that foxes express phenotypic plasticity in daily activity timing across the year, ranging from nocturnal to diurnal to crepuscular rhythms depending on the individual and time of year. Most notably, foxes increased the proportion of daytime activity as seasonal temperatures decreased. Overall, activity patterns of foxes were consistent with the circadian thermoenergetics hypothesis, which posits that animals that switch their patterns of activity do so to coincide with the most energetically favorable time of day. In contrast to foxes, skunks exhibited little behavioral plasticity, appearing strictly nocturnal across the year. While the duration of skunk activity bouts increased with the duration of night, timing of activity onset and offset extended into daytime hours during summer when the duration of darkness was shortest. Analysis of temporal niche overlap between foxes and skunks suggested that niche overlap was highest during summer and lowest during winter and was dictated primarily by temporal niche switching in foxes, rather than skunks. Collectively, our results highlight how interspecific asymmetries in behavioral plasticity drive dynamic patterns of temporal niche overlap within an island carnivore community.

Pattern and timing of mitochondrial divergence of island spotted skunks on the California Channel Islands

AbstractIsland spotted skunks (Spilogale gracilis amphiala) are a rare subspecies endemic to the California Channel Islands, currently extant on Santa Cruz and Santa Rosa islands. How and when skunks arrived on the islands is unknown, hindering decision-making about their taxonomic status and conservation priority. We investigated these questions by sequencing the complete mitochondrial genomes of 55 skunks from the two islands and mainland (California and Arizona) and examining phylogenetic patterns and estimations of isolation times among populations. Island spotted skunks grouped in a single monophyletic clade distinct from mainland spotted skunks. A haplotype network analysis had the most recent common ancestral haplotype sampled from an individual on Santa Rosa, suggesting both islands were colonized by a single matriline. Additionally, no haplotypes were shared between skunk populations on the two islands. These patterns imply that both island populations were derived from a common ancestral population shortly after establishment and have remained isolated from each other ever since. Together with divergence estimates from three methods, this topology is consistent with colonization of the super-island, Santarosae, by a single ancestral population of spotted skunks in the early Holocene, followed by divergence as the sea level rose and split Santarosae into Santa Cruz and Santa Rosa islands 9,400–9,700 years ago. Such a scenario of colonization could be explained either by rafting or one-time transport by Native Americans. Given their distinct evolutionary history, high levels of endemism, and current population status, island spotted skunks may warrant management as distinct evolutionarily significant units.

Role of microhabitat and temporal activity in facilitating coexistence of endemic carnivores on the California Channel Islands

AbstractMost extinctions worldwide have occurred on islands, primarily due to interactions with exotic species, but rarely due to interactions among endemic species. This potential exists on two of the California Channel Islands, Santa Cruz and Santa Rosa, as endemic island spotted skunks (Spilogale gracilis amphiala) appear to have rapidly declined to rarity, possibly due to interference competition with endemic island foxes (Urocyon littoralis). Niche partitioning is expected in response to interference competition; hence, it is surprising that skunks and foxes show extensive overlap in macrohabitat use and circadian activity. However, the role of microhabitat associations and fine-scale temporal activity in facilitating coexistence of the two species has not been explored. We evaluated microhabitat associations of island spotted skunks and island foxes across both islands using data from live traps and wildlife cameras collected during 2015–2017, and we analyzed fine-scale temporal activity using camera data from 2016 and 2017. On both islands, skunks had a positive response to ground-level cover provided by rugged topography or woody vegetation such as shrubs or trees, whereas foxes had a weak or negative response, suggesting partitioning of these microhabitat characteristics. Additionally, on both islands the peak in timing of skunk activity offset the peak for foxes, which implies that skunks use fine-scale adjustments in activity to avoid foxes. Past grazing by exotic herbivores likely reduced habitat refuges for skunks; however, as vegetation on both islands recovers, regrowth of shrubs and trees may provide cover that will improve prospects for coexistence of island spotted skunks and island foxes.

Assessing Methods for Detecting Island Spotted Skunks

ABSTRACTIsland spotted skunks (Spilogale gracilis amphiala) are endemic to 2 of the California Channel Islands (CA, USA)—Santa Cruz and Santa Rosa. The status of skunks is uncertain, although incidental captures in traps set for island foxes (Urocyon littoralis) suggest that skunks have declined to low numbers. We superimposed wildlife cameras at fox traps in 2016 and 2017 to provide a second measure of skunk detectability. On both islands, detection rates of skunks with fox traps (0.92/100 operating nights) and with cameras (0.72/100 operating nights) did not differ during summer, indicating the 2 methods are of similar reliability for detecting skunks. In 2017, skunk detections with cameras increased from summer to early winter, suggesting monitoring in winter may improve survey efforts. Low detection rates of island spotted skunks (<1/100 operating nights) were comparable to those of other spotted skunk populations that are considered rare. © 2020 The Wildlife Society.

PREVALENCE AND SEVERITY OF SKUNK CRANIAL WORM (SKRJABINGYLUS CHITWOODORUM) DAMAGE INCREASE WITH PRECIPITATION IN SPOTTED SKUNKS (SPILOGALE SPP.).

Eastern and western spotted skunks (Spilogale putorius and Spilogale gracilis) serve as definitive hosts for skunk cranial worm (Skrjabingylus chitwoodorum), a metastrongylid nematode that spends its adult stage inhabiting the frontal sinuses of the host cranium. Skunk cranial worm can cause severe damage to the skull of spotted skunks, and this damage is identifiable in preserved specimens. We visited six mammal collections between 2016 and 2018 and used 578 spotted skunk skull specimens to identify patterns in prevalence and severity of skunk cranial worm damage in spotted skunks. Specimens were collected between 1895 and 1981 from across the US. We assessed effects of host genetic clade, collection year, precipitation, and sex on prevalence and severity rates. We hypothesized that the midwestern genetic clade (plains spotted skunk, Spilogale putorius interrupta), which experienced a range-wide population decline in the mid-1900s, would experience the highest infection and severity rates. We expected precipitation, but not sex to influence infection and severity. Our top models indicated that host genetic clade, precipitation in the year prior to specimen collection, and the year prior to specimen collection best predicted prevalence and severity of skunk cranial worm. We suggest the positive association with precipitation is a result of local availability of gastropods, the intermediate host for skunk cranial worm. There was a negative association between prior year and prevalence, but the severity of damage increased over time for all clades. Given concerns over population declines of spotted skunks as well as observations of increasing damage over the past century, there is a need for further research on the impacts of cranial worm infection on individual-scale behavior, reproduction and survival, and on population-scale demographics.

Biotic factors influencing the unexpected distribution of a Humboldt marten (Martes caurina humboldtensis) population in a young coastal forest.

Pacific martens (Martes caurina) are often associated with mature forests with complex structure for denning, resting, and efficient hunting. Nonetheless, a small isolated population of the Humboldt subspecies of Pacific martens (Martes caurina humboldtensis) occupies a narrow strip of young, coastal forest (< 70 years old) but not inland mature forest in the central Oregon Coast Range. We examined factors contributing to this unexpected distribution of martens by 1) analyzing marten diets using DNA metabarcoding to assess 90 scats, 2) using camera traps to assess differences in the relative abundances of prey, competitors, and predators across a coastal to inland gradient of vegetation types, and 3) quantifying differences in extent of fruit-producing shrubs and vegetation structure within vegetation types. Diets of martens were diverse (12, 10, and 3 species of birds, mammals, and amphibians respectively), and most fall and winter scats contained fruit. Voles, mice, and varied thrushes (Ixoreus naevius) were dominant prey items. Voles, mice, and most birds, but not varied thrushes, were more commonly observed in the coastal shrub-dominated forest than in inland forest. The coastal shrub-dominated forest had the highest diversity of vertebrates and potential prey overall. Bobcats (Lynx rufus), a key potential predator, were more commonly detected in inland forest. Of potential competitors, western spotted skunks (Spilogale gracilis) were more commonly detected in inland forest, with gray foxes (Urocyon cinereoargenteus) and raccoons (Procyon lotor) detected almost exclusively in coastal forests. Vegetation in coastal forests appears to provide, at least seasonally, more prey and fruit, and more overhead shrub cover compared with inland forest. Remaining plausible hypotheses for the restricted distribution of marten to coastal forests include increased prey, fruit, and overhead cover, and reduced predation risk from bobcats.

Avian and Skunk Predation of Ashy Storm-Petrels at Santa Cruz Island, California

Avian and mammalian predation of Ashy Storm-Petrels (Oceanodroma homochroa) were documented during monthly nest monitoring in 1995–1998 and 2005–2015 and once-per-year monitoring in 1999–2004 at 5 colonies at Santa Cruz Island, California. Throughout the study period, predation by Barn Owls (Tyto alba) was documented at the sea cave colonies, and at Orizaba Rock, and likely contributed to reduced breeding success at Bat Cave in 1995–1997. Recent predation by Common Ravens (Corvus corax) caused reduced breeding success each year in 2012–2015 at Orizaba Rock (35%–48%) and in 2013 and 2015 at Bat Cave (49%–52%). Raven predation appears to be developing into a larger long-term problem that may require additional management actions, but efforts have focused on deploying artificial nests at Bat Cave to provide more protected sites. Two sea cave colonies where skunks previously had not been detected experienced major adult mortality due to unusual predation events by island spotted skunks (Spilogale gracilis amphiala) in 2005 and 2008. At Bat Cave in 2005, 2 skunks were trapped after they had killed at least 76 Ashy Storm-Petrel adults. Prior to this mortality event, the colony contained 64–97 nests per year in 1995–1997, with low breeding success (49%–59%) related largely to organochlorine pollutants. After the skunks were caught, nest numbers increased from 19 in 2006 to 100 in 2015, with variable but generally higher breeding success (49%–90%). At Cavern Point Cove Caves in 2008, 2 skunks were trapped after killing at least 32 adults. Prior to the mortality event, this colony contained 11–17 nests per year in 1995–1997, with a lower breeding success rate of 20%–47%. Nest numbers increased from 2 in 2009 to 10 in 2015, with a variable but higher rate of breeding success (50%–80%). Skunk predation events may have been related to temporarily higher skunk populations at Santa Cruz due to low numbers of island foxes (Urocyon littoralis santacruzae). Deer mice (Peromyscus maniculatus santacruzae) were not significant predators of Ashy Storm-Petrels at Santa Cruz Island.

&lt;b&gt;REGISTROS NOTABLES DE MAMÍFEROS PARA LA RESERVA DE LA BIÓSFERA SIERRA GORDA DE GUANAJUATO, MÉXICO&lt;b&gt;

ABSTRACTWe present distribution range extentions for five species of mammals from the Sierra Gorda de Guanajuato Biosphere Reserve in state of Guanajuato, Mexico. These are two felids: Lynx rufus and Puma concolor, as well as the western speckled skunk Spilogale gracilis, the peccari Dicotyles crassus, and the coati Nasua narica. The presence of these records reflects the importance of the Sierra Gorda de Guanajuato Biosphere Reserve as one of the main protected natural areas of Guanajuato, Mexico, since this area constitutes a natural bridge between species of neartic and neotropical affinity. This type of study reaffirms the need to continue conducting regional and local biological inventories in Mexico.Key words: Range extensión, camera-traps, Victoria, Guanajuato, biological corridor.Palabras clave: Distribución, cámaras trampa, Victoria, Guanajuato, corredores biológicos.

Phylogeography of a widespread small carnivore, the western spotted skunk (Spilogale gracilis) reveals temporally variable signatures of isolation across western North America.

We analyzed phylogeographic patterns in the western spotted skunk, Spilogale gracilis Merriam, 1890 (Carnivora: Mephitidae) in relation to historical events associated with Pre‐Pleistocene Divergence (PPD) and Quaternary climate change (QCC) using mitochondrial DNA from 97 individuals distributed across Western North America. Divergence times were generated using BEAST to estimate when isolation in putative refugia occurred. Patterns and timing of demographic expansion was performed using Bayesian skyline plot. Putative climatic refugia resulting from Quaternary climate change were identified using paleoecological niche modeling and divergence dates compared to major vicariant events associated with Pre‐Pleistocene conditions. We recovered three major mitochondrial clades corresponding to western North America (California, Baja, and across the Great Basin), east‐central North America (Texas, central Mexico, New Mexico), and southwestern Arizona/northwestern Mexico. Time to most recent common ancestor for S. gracilis occurred ~1.36 Ma. Divergence times for each major clade occurred between 0.25 and 0.12 Ma, with signature of population expansion occurring 0.15 and 0.10 Ma. Ecological niche models identified three potential climatic refugia during the Last Interglacial, (1) west coast of California and Oregon, (2) northwestern Mexico, and (3) southern Texas/northeastern Mexico as well as two refugia during the Last Glacial Maximum, (1) western USA and (2) southern Texas/northeastern Mexico. This study supports PPD in shaping species‐level diversity compared to QCC‐driven changes at the intraspecific level for Spilogale, similar to the patterns reported for other small mammals (e.g., rodents and bats). Phylogeographic patterns also appear to have been shaped by both habitat and river vicariance, especially across the desert southwest. Further, continuing climate change during the Holocene coupled with anthropogenic modifications during the Anthropocene appears to be removing both of these barriers to current dispersal of western spotted skunks.

The importance of motivation, weapons, and foul odors in driving encounter competition in carnivores.

Encounter competition is interference competition in which animals directly contend for resources. Ecological theory predicts the trait that determines the resource holding potential (RHP), and hence the winner of encounter competition, is most often body size or mass. The difficulties of observing encounter competition in complex organisms in natural environments, however, has limited opportunities to test this theory across diverse species. We studied the outcome of encounter competition contests among mesocarnivores at deer carcasses in California to determine the most important variables for winning these contests. We found some support for current theory in that body mass is important in determining the winner of encounter competition, but we found that other factors including hunger and species-specific traits were also important. In particular, our top models were "strength and hunger" and "size and hunger," with models emphasizing the complexity of variables influencing outcomes of encounter competition. In addition, our wins above predicted (WAP) statistic suggests that an important aspect that determines the winner of encounter competition is species-specific advantages that increase their RHP, as bobcats (Lynx rufus) and spotted skunks (Spilogale gracilis) won more often than predicted based on mass. In complex organisms, such as mesocarnivores, species-specific adaptations, including strategic behaviors, aggressiveness, and weapons, contribute to competitive advantages and may allow certain species to take control or defend resources better than others. Our results help explain how interspecific competition shapes the occurrence patterns of species in ecological communities.

Data from camera surveys identifying co-occurrence and occupancy linkages between fishers (Pekania pennanti), rodent prey, mesocarnivores, and larger predators in mixed-conifer forests.

These data provide additional information relevant to the frequency of fisher detections by camera traps, and single-season occupancy and local persistence of fishers in small patches of forest habitats detailed elsewhere, “Landscape Fuel Reduction, Forest Fire, and Biophysical Linkages to Local Habitat Use and Local Persistence of Fishers (Pekania pennanti) in Sierra Nevada Mixed-conifer Forests” [10]. The data provides insight on camera trap detections of 3 fisher predators (bobcat [Lynx rufus]). Coyote [Canis latrans], mountain lion [Puma concolor], 5 mesocarnivores in the same foraging guild as fishers (gray fox [Urocyon cinereoargenteus]) ringtail [Bassariscus astutus], marten [Martes americana], striped skunk [Mephitis mephitis] spotted skunk [Spilogale gracilis], and 5 Sciuridae rodents that fishers consume as prey (Douglas squirrel [Tamiasciurus douglasii]), gray squirrel [Sciurus griseus], northern flying squirrel [Glaucomys sabrinus], long-eared chipmunk [Neotamias quadrimaculatus], California ground squirrel [Spermophilus beecheyi]. We used these data to identify basic patterns of co-occurrence with fishers, and to evaluate the relative importance of presence of competing mesocarnivores, rodent prey, and predators for fisher occupancy of small, 1 km2 grid cells of forest habitat.

Non-Invasive Survey of Forest Carnivores in the Northern Cascades of Oregon, USA

Several species of forest carnivores are of state or federal concern in Oregon and are or may be sensitive to timber management practices, wildfires, climate change, and other large-scale disturbances. We implemented a non-invasive survey of forest carnivores in the northern Cascades of Oregon during fall–spring, 2012–2014. We collected 111,148 images from 21 elevated and 39 ground-level baited camera stations located from 586 to 2237 m in elevation. We detected (≥1 image) Red Fox (Vulpes vulpes) at 9 ground stations, of which 4 also detected Coyote (Canis latrans). We detected American Marten (Martes americana) at 63% of all stations (elevation range = 1252–2237 m), including 5 of 7 stations located in areas that experienced wildfires since 1996 that covered >5000 ha. Other forest carnivores detected included Bobcat (Lynx rufus), Black Bear (Ursus americanus), Mountain Lion (Puma concolor), Northern Raccoon (Procyon lotor), American Mink (Neovison vison), weasel (Mustela spp.), and skunk (Mephitis mephitis, Spilogale gracilis); but we did not detect Wolverine (Gulo gulo), Canada Lynx (Lynx canadensis), Fisher (Martes pennanti), or Gray Wolf (Canis lupus). Future periodic non-invasive surveys of forest carnivores may provide information about changing species composition and distribution, especially in relation to climate change, vegetation succession, and potential recolonization by Gray Wolves.

Registro de presencia y actividades de algunos mamíferos en el Desierto Chihuahuense, México

Introduction: Photographic records are useful tools that had strengthen wildlife mammal studies as a noninvasive methodology providing a wide variety of information. The objective of this study is to document with images (automatic - trail cameras and manually – personal cameras) the species of mammals inhabiting the Mapimi Biospere Reserve (MBR), to highlight the morphologic characteristics that distinguish them, to record the area and vegetation type where each species was found and to determine some of their daily activities. Methods: Between 2009 and 2014, twelve field trips were made to Mapimi. In each trip we placed six trail cameras each at five locations (30 cameras total) for 24 h during six consecutive days, with 51,840 h photographic effort. Two sets of six cameras were placed in grassland habitat and three in shrubland habitat. Each camera was baited with 300 g of alfalfa mixed with sand in a tray placed 3 m from the camera. Between 2011 and 2014 two additional cameras were set to monitor a natural pond on the slope of a small mountain (San Ignacio) in the area with 5,760 h of photographic effort. In total we had 57,600 h of photographic effort. Images were also obtained from manual cameras of the authors while engaged in various research projects in the area with more than 2,000 photographs. These data for some species are directly from animals captured in the locality. Their main morphologic characteristics were highlighted, specific places, type of vegetation where each species was found and some of their daily activities. Results: A total number of five orders, 12 families, 27 genera and 31 species were recorded, representing 49 % of mammals known in the Reserve. With trail cameras 1,714 photos were taken and 15 species were recorded (Table 1). The species with highest number of records were Dipodomys nelsoni ( n = 610), D. merriami ( n = 469) and Netoma leucodon ( n = 335). The ones with the lowest number of photos were Ictidomys mexicanus ( n = 48) and Sylvilagus audubonii ( n = 46, Figure 1).Trail cameras recorded five genera where the species level could not be determined: Myotis sp., Chaetodipus sp. , Peromyscus sp., Ictidomys or Xerospemorphilus . With manual cameras more than 2,000 photos were taken and thirty species were photographed, only 16 were recorded with this method (Table 1). The collared peccary ( Pecari tajacu) was the single species recorded only by trailed cameras. Discussion and Conclusions: Results obtained demonstrated that with trail cameras, morphological characteristics that distinguish most mammalian species can be observed clearly for most small, medium and large species. For some small species (such as Heteromyidae and Muridae) their features cannot be easily noted so their proper identity is difficult to determine. It is also important to discuss that only half of the known mammal diversity in the locality was recorded with trail cameras. Some small (such as Heteromyidae and Muridae rodents and bats), medium (as skunks) or large size species (as pumas) were not recorded with them, even though these cameras are generally considered a very effective method for mammalian inventories. As our results do not support this idea, we strongly recommend to combine direct trapping methods with trail cameras to get more complete and more realistic mammalian inventories. The highest numbers of records obtained with trail cameras were of Dipodomys nelsoni , D. merriami and Netoma leucodon , reflecting their numerical dominance in the ecosystem. Lower number of records of Sylvilagus audubonii, squirrels, deer , peccaries and other mammals are related with their low abundance and they occur only in very specific areas. The low numbers found of Lepus californicus were contradictory with previous studies, where they were much more frequently recorded. Skunks inhabit rocky and hills parts in the Reserve, and the presence of Spilogale gracilis was exceptional and as such represents a new record of this species for the Reserve. Documentation of mammalian species through photographic images contributes to different aspects of their biology that had not been addressed before in this location. Cameras allowed updating of information of some species and helped to identify knowledge gaps that can be addressed in the future to contribute to understand the dynamics of the mammal community in the Chihuahuan Desert. Key words: Manual cameras, new record, photographic identification, Spilogale gracilis , trail cameras.