The Eastern Spotted Skunk: Multi-Regional Cooperative Efforts to Address the Decline of a Once Abundant Furbearer

Symposium
ROOM: CC, Room 25B
SESSION NUMBER: 28
 
The Eastern Spotted Skunk (Spilogale putorius) experienced a range-wide decline starting in the 1940?s. Based on harvest records, populations may have declined up to 99% from the early to mid-1900?s. Causes for the decline are unknown, but factors could include habitat loss, changes in agricultural methods, widespread use of pesticides, overharvest, and disease. The Eastern Spotted Skunk is a cryptic and elusive species that does not lend itself to traditional monitoring efforts (e.g., observations, live capture). That, coupled with its status as a furbearer species in most states, resulted in this species having been overlooked by scientists and management agencies until recently. The Plains subspecies (S. p. interrupta) has been petitioned for listing under the Endangered Species Act, and in 2017, the International Union for Conservation of Nature (IUCN) listed the species as vulnerable (i.e., considered to be facing a high risk of extinction). Several states within the Eastern Spotted Skunk?s range have recently reclassified the species as threatened or a species of special concern, while other states have made it a priority species in their Wildlife Action Plans. Because so little is known about the Eastern Spotted Skunk, wildlife managers and researchers across the species? range are collaborating to exchange ideas and enhance our understanding of the species, including the creation of the Eastern Spotted Skunk Cooperative Study Group. The presentations in this symposium are a result of those collaborative efforts and intended to provide the first synthetic update on the ecology of this species from ongoing and recently completed research across the species range.

12:50PM State of the Skunk: What We Know and Don’t Know About Eastern Spotted Skunk Declines and Ecology
  Matthew Gompper
The eastern spotted skunk was once common but is now putatively rare. Here I review our knowledge of the species, with a focus on aspects of the biology and ecology of the species that may underpin its decline, as well as critical topics that remain understudied. Causes of the decline of the species are uncertain, and indeed, the geographic scope of the decline itself is variable. Nonetheless in many states across the former range of the species there is no doubt that dramatic declines occurred. Multiple factors likely contributed to this decline, included landscape change, altered predator communities, overharvest, pathogens, and environmental pollutants. Recent studies of the species have greatly increased our understanding of aspects of the natural history, distribution, habitat ecology and landscape ecology of the species, but there remain significant gaps in our understanding of topics such as feeding ecology, reproductive biology, disease ecology, and the demographics of the taxon. A general rule of thumb in species recovery work is that defining the cause of decline is a necessary first step before management can act to rectify the problem. Unfortunately in the case of the eastern spotted skunk, the initial decline occurred nearly 70 years ago, and it was only recently that the scale and severity of the decline became widely noted. Assuming our limited ability to unequivocally identify the foundation of the decline, necessary management actions aimed at facilitating the persistence of eastern spotted skunks will need to be made with the recognition of this uncertainty.
1:10PM Genetic Variation in the Eastern Spotted Skunk with Emphasis on the Plains Spotted Skunk Subspecies
  Alexandra A. Shaffer; Robert C. Dowler; J. Clint Perkins; Adam W. Ferguson; Molly M. McDonough; Loren K. Ammerman
We present results of an assessment on the genetic variability of the eastern spotted skunk (Spilogale putorius), with a particular emphasis on the potentially endangered plains spotted skunk (Spilogale putorius interrupta), throughout the range of the species. Tissue samples from a variety of sources (including field surveys, state agencies, and museum tissue collections) allowed a detailed assessment of the genetic variability in S. putorius using both microsatellite markers and cytochrome b gene sequences. Our analysis of 119 specimens established that genetic patterns were consistent with the currently accepted taxonomy of the 3 recognized subspecies: S. p. putorius, S. p. ambarvalis, and S. p. interrupta. The differentiation between S. p. putorius and S. p. ambarvalis was less pronounced (FST = 0.178; cytochrome b sequence divergence = 1.2%) than between these subspecies and the plains spotted skunk (average FST = 0.278; cytochrome b sequence divergence = 2.9%). Overall, genetic variability (observed heterozygosity = 0.474, allelic richness = 6.64) in the plains spotted skunk was lower than that seen in common carnivores (striped skunks, raccoons), but slightly higher than some endangered carnivores (black-footed ferret). The heterozygosity levels more closely resemble the levels found within the island spotted skunk (S. gracilis amphiala) from the Channel Islands of California and other vertebrates that have a “threatened” conservation status.
1:30PM The spotted skunks of the Florida dry prairie: insights into resource selection, movement and diet
  Stephen N. Harris; Terry J. Doonan; Erin L. Hewett Ragheb; David S. Jachowski
The eastern spotted skunk (Spilogale putorius) is a small skunk native to eastern North America that has experienced a range-wide decline since the early to mid-1900s. The Florida spotted skunk (S. p. ambarvalis) is the least studied of the eastern spotted skunk’s three subspecies and is endemic to the Florida peninsula. The only prior research on the subspecies was conducted on an Atlantic barrier island, though a recent nest-camera study has identified the subspecies as an important predator of ground-nesting grassland birds in the dry prairie habitat of south-central Florida. To contribute to the knowledge of the Florida subspecies, and to better understand this diminutive carnivore’s role as a nest predator, we conducted studies on the denning, ecology, and dietary habits of the Florida spotted skunk in a dry prairie ecosystem. We studied den site selection of skunks in the dry prairie by fitting 36 skunks with VHF radio-transmitters and tracking them to their den sites, where we measured habitat and den-specific characteristics. Similarly, we studied the fine-scale movements of skunks in the prairie by fitting 23 unique skunks with GPS transmitters. We also collected hair samples from individual skunks and compared these to potential food items using stable isotope analysis to study the makeup of spotted skunk diets in the dry prairie. The results of our studies provide insight into Florida spotted skunk ecology and make it clear that more research is warranted on this subspecies across its range and in other habitats. Our results also highlight some differences in ecology between the Florida spotted skunk and the other two eastern spotted skunk subspecies and will aid in comparisons between these subspecies in the future.
1:50PM Large- and Fine-Scale Habitat Associations of Eastern Spotted Skunks (Spilogale Putorius) in the Central and Southern Appalachian Mountains
  Emily Thorne; Robin Eng; Charles Waggy; Mark Ford; David Jachowski
Eastern spotted skunks (Spilogale putorius) were once regarded as a fairly common furbearer throughout the Appalachian Mountains. Severe population declines in the mid-1900’s have reduced the populations and distribution. Despite listed as vulnerable on the IUCN Red List, little is known about the species’ ecology. Through combined research efforts between Virginia Tech Department of Fish and Wildlife, Virginia Department of Game and Inland Fisheries, U.S. Geological Survey, Clemson University Department of Forestry and Environmental Conservation, South Carolina Department of Natural Resources, and West Virginia Division of Natural Resources, we identified components of landscape- and fine-scale habitat association of skunks regionally. We used a detection/non-detection, baited remote-sensing camera method to estimate detection probability and probability of site occupancy in forested montane areas of VA, NC and SC. Skunks were associated with lower elevations and dense understories. Additionally, we tracked 36 spotted skunks in WV, VA, and NC from March 2015 through November 2017 to assess fine-scale habitat use and den selection. Skunks used a variety of den types: underground burrows, rocky crevices, cavities in live trees and snags, hollow logs, and various anthropogenic structures. Dens were typically located in areas of dense understory cover, coarse woody debris, or emergent rock that offered protection from predators and inclement weather. We recommend that conservation and management efforts of eastern spotted skunks in the central and southern Appalachians should focus on maintaining current occupied areas and increasing habitat connectivity by creating more vegetative understory through prescribed burning or forest harvesting.
2:10PM Distribution and Habitat Use of the Eastern Spotted Skunk in Alabama
  Andrew Edelman; Nicholas Sharp
Eastern spotted skunks (Spilogale putorius) have significantly declined in abundance across their range over the last half century. In Alabama, eastern spotted skunks are a state-protected species of high conservation concern and appear to be relatively rare. Given their secretive and noxious habits, little is known about their basic natural history and distribution in the state. Since 2014, we have studied the distribution and habitat use of eastern spotted skunks in Alabama. Radio-tracking of individuals revealed selection of forested habitat with dense woody cover in the midstory at local and landscape scales. In 2017, we conducted a statewide survey to determine the distribution and landscape associations of eastern spotted skunks. We collaborated with local land managers to deploy 209 camera traps across public lands in Alabama. We also encouraged the public to report sightings of skunks through social media and iNaturalist.org. Camera trap surveys only detected 2 eastern spotted skunks, whereas citizen scientists reported over 20 sightings, the majority of which included coordinates and a picture. At the landscape scale, probability of eastern spotted skunk presence increased with forest cover and elevation, which are more associated with areas north of the fall line. Our results suggest the species is still widely distributed across the state, but likely rare or highly localized to areas of more continuous suitable habitat. Our research highlights the effectiveness of combining traditional science and citizen scientists in documenting rare and elusive species.
2:30PM Refreshment Break
3:20PM Current Status of the Plains Spotted Skunk in Texas
  Robert C. Dowler; J Clint Perkins; Alexandra A. Shaffer; Jon Paul Pierre; Brad D. Wolaver
There is good evidence that the plains spotted skunk (Spilogale putorius interrupta) has experienced a decline across most of its range in the central United States. Despite the pattern of decline, little is known about the status of populations across much of that distribution. We report on a 3-year study to determine areas of Texas where existing populations have been documented in the recent past. We selected sites for sampling based on a species distribution model (Maxent) using data from historical museum specimens to predict potential suitable habitat throughout the state of Texas. Ten counties with elevated probability of occurrence were selected for sampling. A combination of live-traps, track plates, and camera traps (n = 120) were used during 8-day survey periods in 10 counties from 2015 through 2017. These methods documented detections of plains spotted skunks (n = 12) in 4 of the 10 sites sampled. All methods of detection were successful, but cameras and live traps out-performed track plates. Crowd-sourced approaches and camera trapping by citizen scientists revealed an additional 82 occurrences in the state, 79 of which were since 2009. These recent records were used to produce a species distribution model that provides relative probability of occurrence for the plains spotted skunk in the state. Our land-change mapping revealed potential anthropogenic threats to habitats at 2 of the sites (Katy Prairie and Fort Hood), which also had robust populations of plains spotted skunks based on 25 and 51 detections, respectively.
3:40PM Spotted Skunk Surveys in Wyoming: An Update
  Merav Ben-David; Zachariah Bell; Robert Riotto; Douglas Keinath
The plains spotted skunk (Spilogale putorius interrupta) was petitioned for listing under the Endangered Species Act (ESA) due to large, range-wide declines in abundance. Eastern (S. putorius) and western (S. gracilis) spotted skunks are considered distinct based on geography, mitochondrial DNA and differing reproductive traits. However, the two species cannot reliably be distinguished by morphology. Also, the validity of the S. p. interrupta subspecies is unclear. Central Wyoming is one of few locations where the two species could co-occur, possibly leading to sympatry and hybridization. We used 87 known locations of spotted skunks derived from camera traps (WGFD, n = 16 and the UWYO, n = 9) and verified historic and new records collected through public outreach campaign (n = 62) to determine habitat associations of these carnivores. Analysis suggested that spotted skunks in Wyoming use rocky outcrops near riparian areas disproportionately more than available (χ2 test, p < 0.001). Further, 92% of all locations had <5% canopy cover. Based on these results, we used GRITS spatially balanced, random sampling to generate 900 survey locations near rocky outcrops and/or water throughout Wyoming. Between June and November 2017, we deployed 3 cameras traps spaced at 250-500m at over 200 of these sites (i.e., > 600 camera trap locations). Cameras were baited with 3-5 dead pheasant chicks and were laced with commercial scent lure. We detected spotted skunks at 22 of these sites and captured 28 individuals in Tomahawk live traps. Tissue and blood samples were collected from all individuals. Currently, we are performing genomic analyses on DNA extracted from these live-captured individuals, as well as from 38 museum specimens and samples shared through collaborative projects. Our goal is to develop reliable genetic markers for both species and delineate their distributions across the state.
4:00PM Disease Management Challenges for Eastern Spotted Skunks
  Bonnie E. Gulas-Wroblewski
Infectious disease can impact the viability of a species directly by causing host mortality and/or indirectly by reducing the fitness and reproductive success of threatened species. Attributes of eastern spotted skunks’ (Spilogale putorius) habitat use, behavior, and natural history traits expose them to a diversity of infectious pathogens. A number of diseases have been recorded in eastern spotted skunks across the United States, but their impact on the health of individual skunks and on the overall fitness of eastern spotted skunk populations has yet to be explored. This presentation will provide a concise review of the infectious pathogens that have been detected in eastern spotted skunks with a discussion of the possible importance these diseases hold for historic and current population declines in the Plains subspecies. I will outline the current knowledge gaps in our understanding of eastern spotted skunk health along with the on-going, collaborative research programs that are seeking to fill some of these gaps. I will conclude with a summary of the challenges of managing individual- to population-level health of S. putorius in light of the cryptic nature of the species and their potentially-increasing exposure and susceptibility to infectious diseases from habitat loss and fragmentation, climatically-driven range expansions of disease agents, and transmission of pathogens across the wildlife-domestic interface.
4:20PM Advancing Mesocarnivore Conservation: the Eastern Spotted Skunk Cooperative Study Group Model
  David Jachowski
Mesocarnivores are imperiled globally, yet receive less conservation attention than larger apex carnivores. To prevent extinction and promote effective conservation in the current backlog of federal endangered species listing decisions, action often needs to be taken prior to formal listing under endangered species legislation. However, this can be difficult to implement without the associated release of federal funds and mandates to implement recovery that come with legal listing. In 2015, the Eastern Spotted Skunk Cooperative Study Group (ESSCSG) was formed to (1) enhance communication, (2) identify management, conservation and research priorities, and (3) facilitate collaboration regarding this little understood species. In 2018, without federal government oversight or assistance, this group of >90 concerned biologists from 23 states completed the first conservation plan for this species. Similar models have recently been implemented for species at risk of being listed under endangered species legislation, but the ESSCSG model is likely one of the first intensive efforts ahead of a species even being petitioned for listing under the ESA. Thus, the creation and implementation of the ESSCSG provides a new kind of road map for objective, “bottom-up”, science-based conservation planning at a regional scale that could be implemented for other, long-overlooked species of potential conservation concern.
4:40PM Linking Spotted Skunk Research with Management
  Kimbery Horndeski
In today’s rapidly changing world, promoting conservation is challenging as species are exposed to numerous stressors and threats from multiple activities and stakeholders. For conservation to be effective, though, stakeholders, along with researchers, must be involved in the process in order to promote a healthy dialogue and identify the social and environmental issues that are of great importance for the species. This presentation will focus on case studies that elaborate on how state and federal agencies can engage stakeholders, and industries, even with differing views, and promote voluntary conservation actions in order to link research to effective conservation practices. This presentation will also focus on “lessons learned” that can be applied to current and future conservation projects.

 
Organizers: Colleen Olfenbuttel, North Carolina Wildlife Resources Commission, Pittsboro, NCKimberly A. Horndeski, Texas Comptroller of Public Accounts, Austin, TXDavid S. Jachowski, Clemson University, Clemson, SC
 
Supported by: The SE Section of the Wildlife Society; The TWS Biological Diversity Working Group; The TWS Forestry and Wildlife Working Group

Symposium
Location: Cleveland CC Date: October 8, 2018 Time: 12:50 pm - 5:00 pm