Mesocarnivores

Contributed Paper
ROOM: CC, Room 26B
SESSION NUMBER: 50
 

3:20PM Using Species Distribution Modeling to Target Eastern Spotted Skunk Research and Management Efforts
Summer D. Higdon; Maggie MacPherson; Matthew E. Gompper
The eastern spotted skunk (Spilogale putorius) is a small, elusive mephitid native to the eastern and Midwestern U.S. and is currently listed as vulnerable on the IUCN Red List. Beginning in the 1940s, their populations declined range-wide and have not recovered. Reasons for the decline remain unknown, but modernized agriculture, increasing use of pesticides, habitat loss, overharvest, and disease have all been implicated. We developed a species distribution model (SDM) using presence-only data collected from track plates and camera traps across three national forests throughout the Ozark and Ouachita mountain regions from 2005-2018. The SDM was used to project potential habitat for the plains spotted skunk subspecies (S. p. interrupta) found in this region, which is petitioned to be listed federally under the Endangered Species Act. As our SDM was trained using track plate and camera trap data in Ouachita, Ozark, and Mark Twain National Forests, we were able to either collect or build fine-scale data layers that included environmental variables such as land-use type, canopy cover, understory density, coarse woody debris, time since burn, and distance to roads. We approached building the predictive SDM to limit model over-fitting by restricting our spatial predictions to within three National Forests, using fine-scale spatial resolution, and restricting the number of pseudo-absences used as background points. This enabled us to create actual distribution models (ADMs) characterizing the realized niche of this range-restricted subspecies, rather than potential distribution models (PDMs) that result from overfitted SDMs. We discuss how the resultant model may be used to prioritize future research and management efforts throughout the Ozark and Ouachita mountain regions and how similar approaches could be applied across the greater eastern spotted skunk range.
3:40PM Evaluating Methods for Detecting and Estimating Occupancy for a Rare Endemic Carnivore, the Island Spotted Skunk of the California Channel Islands
Ellie Bolas; Kevin Crooks; Rahel Sollmann; Paula Power; Christina Boser; Erin Boydston; Victoria Bakker; Adam Dillon; Dirk Van Vuren
Two of the California Channel Islands, Santa Cruz and Santa Rosa, are unusual in that they support two endemic carnivores, the island spotted skunk (Spilogale gracilis amphiala) and the island fox (Urocyon littoralis). The relationship between the two is not well understood, however, fluctuations in skunk numbers appear to be influenced by changing fox abundance. Annual monitoring of foxes via live-trapping is performed on both islands and skunks are also captured, providing long-term capture histories for both species. On both islands over the last four years, fox populations have increased and captures of skunks have decreased to extreme rarity, but it is unknown if these incidental skunk captures accurately reflect skunk occurrence and abundance. Our objective was to assess whether trapping to monitor island foxes is an effective means of detecting and quantifying island spotted skunks. Thirty remote cameras were deployed at trap sites on 10 fox trapping grids on each island for 6 months, concurrent with trapping efforts for foxes. Occupancy modeling was used on data from both trapping and remote cameras, and detection probabilities were compared to determine if trapping provides a reliable index of skunk occurrence for each island. Preliminary analysis revealed differences in detections between traps and cameras for skunks. On Santa Cruz Island, skunks were detected on 5 of 10 trapping grids via cameras but only 3 of 10 trapping grids via trapping, and on Santa Rosa, skunks were detected at 9 of 10 trapping grids via camera and only 4 of 10 grids via trapping. Further, there appear to be seasonal differences in skunk occupancy that were detected by cameras but not traps. These results can assist island managers in developing comprehensive monitoring strategies to support conservation of island spotted skunks.
4:00PM Home Range and Resource Selection Patterns of a Recovering Swift Fox Population in Northeastern Montana: Implications for Statewide Habitat Suitability and Connectivity
Andrew Butler; Kristy Bly; Heather Harris; Bob Inman; Axel Moehrenschlager; Donelle Schwalm; David Jachowski
Swift foxes (Vulpes velox) are listed as a species of conservation concern over much of their range. Montana’s population of swift fox was extirpated by 1969 and despite reintroductions to southern Canada, there is still a significant range gap between northern populations in Montana and Canada, and those in Wyoming and South Dakota. In addition, there is no rigorous study of the resource needs of foxes or the availability of fox habitat across this area. To address these knowledge gaps, we used hidden Markov models as well as resource utilization functions to examine several hypotheses of how movement state and landscape characteristics influence space use at the home range scale, and then extrapolated these results across Montana. Our analysis indicated that resource selection patterns differed by behavioral state. In the sedentary and restricted movement states, swift fox selected for areas with high topographic roughness and selected for areas near roads and crop fields. In the exploratory state, swift fox avoided areas with topographic roughness and further from roads, and selected for areas near roads but away from crop fields. The results of this study provide managers with important information on the current resource needs of the recovering population of swift fox as well as where current swift fox habitat exists throughout the state and potential corridors between suitable areas, which can guide future conservation efforts.
4:20PM Consequences of a Disease-Induced Fox Population Decline on the Occurrence and Trap Success of Other Mesocarnivores in a Barrier Island Ecosystem
Kathleen Black; Sarah Karpanty; James Fraser; Daniel Catlin; Claire Helmke; Camron Robertson
A sarcoptic mange outbreak resulted in the die-off and nearly year-long absence of red foxes (Vulpes vulpes) on the eastern portion of Fire Island, New York beginning in April 2016. We sought to examine the consequences of this absence on the occurrence of two other common mesocarnivore species in the area: raccoon (Procyon lotor) and feral cat (Felis catus). We used data collected during remote camera surveys conducted each fall from 2015-2017 to estimate trap success, occurrence, and detection probabilities for all 3 species during each survey season and used an occupancy modeling framework to identify key habitat factors influencing species occurrence. Before the die-off, foxes were the most widespread predator, with an estimated occurrence of 0.86 (SE 0.06, Fall 2015). Following the fox die-off in Spring 2016, raccoon occurrence increased from 0.80 (SE=0.08, Fall 2015) to 0.96 (SE=0.03, Fall 2016), despite the lethal removal of >12 individuals between our 2015 and 2016 surveys. Raccoon trap success also increased noticeably in the absence of foxes. Feral cat occurrence decreased from 0.40 (SE=0.09, Fall 2015) to 0.29 (SE=0.09, Fall 2016), while feral cat trap success did not change substantially. After foxes returned to the area in late March 2017, with an estimated occurrence of 0.83 (SE=0.12) during our Fall 2017 surveys, raccoon occurrence decreased to 0.84 (SE=0.06, Fall 2017), and raccoon trap success also decreased substantially. Feral cat occurrence increased back to 0.34 (SE=0.08, Fall 2017), and feral cat trap success increased slightly. Our results suggest a negative correlation between red fox presence and raccoon occurrence and frequency of detection, along with a possible positive correlation between red fox presence and feral cat occurrence.
4:40PM Weasely Recognized Or Stoataly Camouflaged: Quantifying Coat Color of a Cryptic Predator
Brandon M. Davis; L. Scott Mills
At least 21 species of birds and mammals across the globe undergo seasonal changes in coloration, molting white in winter to match snow cover to reduce predation risk from visually hunting predators. One of the most persistent and widespread signals of climate change in the northern hemisphere, however, is a reduction in the number of days with snow on the ground. As snow duration decreases, animals in white winter coats become more conspicuous against snowless ground. For example, camouflage mismatched snowshoe hares (Lepus americanus) suffer increased mortality compared to camouflaged hares. Yet, the generality of this climate-induced camouflage mismatch across species is unknown. Given the adaptive value of seasonal camouflage against local snow duration, we hypothesize that sympatric color molting species would show convergent coat color phenology. Therefore, we documented coat color phenology of three sympatric coat color changing species in Montana; short-tailed weasels (Mustela erminea), long-tailed weasels (Mustela frenata), and snowshoe hares. The cryptic nature of weasels meant that we could not visually monitor their coat color using direct observation as we have done with snowshoe hares. Therefore, we used a non-invasive sampling framework consisting of remote cameras and bait tubes to quantify coat color phenology for all 3 species, including molt initiation, rate, and completion. To date in our first two field seasons we deployed >50 remote cameras over >6000 trap nights. In that time we detected > 600 photographic hare events and 300 photographic weasel events. Although we are currently completing our analysis it appears that there may be phenology differences between hares and weasels. We conclude that camera trapping is a useful tool for quantifying phenology of sympatric coat color changing species, contributing to the growing knowledge base to determine the potential scope for evolutionary rescue to climate change in wildlife populations.

 

Contributed Paper
Location: Cleveland CC Date: October 9, 2018 Time: 3:20 pm - 5:00 pm