Finding the elusive eastern spotted skunk

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Documentation of the mid-century eastern spotted skunk population decline by Gompper and Hackett (2005).

The eastern spotted skunk is an elusive, potentially rare and endangered species of skunk native to much of the eastern US between the Rockies and the Appalachian Mountains. The species was common throughout its range at the beginning of the twentieth century and people often saw eastern spotted skunks on family farms. During the 1940s and 1950s however, eastern spotted skunk populations crashed. The population decline is well documented, but reasons for the crash remain unclear. Hypotheses for the decline range from the expansion and modernization of agriculture to overharvest to disease. Likely, a combination of several concurrent factors lead to the decline. Eastern spotted skunk populations never recovered, remaining at low levels across much of their historic range.

Today, researchers are working with state wildlife agencies to identify where eastern spotted skunks are and determine which resources they need to maintain healthy populations. In some states, large-scale surveys for eastern spotted skunks resulted in no sightings, suggesting the species is locally extinct in parts of its historic range. Other states have identified populations and are working to understand whether the populations are at a healthy level.

In Arkansas, eastern spotted skunks were historically present across the entire state and recent surveys have revealed the species still has strongholds in the Ouachitas, or the western region of the state. It was with this knowledge the Arkansas Game and Fish Commission funded my research to determine whether eastern spotted skunks are present in the Ozarks, and if so, which resources they’re using. I conducted a large-scale camera trap survey in north-central Arkansas to answer these important questions. Although I recorded eastern spotted skunks at some camera trap sites, preliminary results suggest the species occurs at extremely low population levels in this part of the state.

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An eastern spotted skunk visits a camera trap site in north-central Arkansas.

Using the information gathered from my camera survey, I decided to produce a species distribution model. This type of model uses presence-only data to evaluate where a species is most likely to be present based on characteristics of locations where we know eastern spotted skunks spend time. Using presence-only data means that I will only use camera trap locations where eastern spotted skunks were recorded. For example, from approximately 75 camera trap locations, eastern spotted skunks were photographed at only 4 sites. Failure to record an eastern spotted skunk at a camera trap site doesn’t necessarily mean the species is absent at that site; it simply means we don’t know for sure that eastern spotted skunks use that area. Thus, the locations where I recorded eastern spotted skunks on camera traps are “known locations.” I will use the 4 known locations where eastern spotted skunks were confirmed and exclude the remaining 71 camera trap locations for my species distribution model.

In addition to the 4 known locations from my camera trap survey, the eastern spotted skunk species distribution model will use an additional 72 known locations from eastern spotted skunk surveys by other researchers in Arkansas and southern Missouri. I will determine what the environment was like at the known locations, including how close they are to roads and other infrastructure, how close they are to water sources, and how dense the forest is at each location. Using this information, the species distribution model will predict where eastern spotted skunks are most likely to be across all of Arkansas and southern Missouri. For example, if most of the known locations are in areas where the forest is thick and dense, the model will predict that eastern spotted skunks are most likely to be in other thickly forested parts of the state and less likely to be in open fields.

Although the large-scale camera trapping survey I conducted resulted in limited eastern spotted skunk photographs, the species distribution model approach allows me to use these data. The final product will be a heat map of Arkansas and southern Missouri, with warm tones suggestive of eastern spotted skunk populations and cool tones meaning eastern spotted skunks are not likely to occur in those areas. The map will be useful for state wildlife agencies as they continue to determine where the species is and create management plans to prevent further population decline of this unique mammal.

 

Will you be at The Wildlife Society Annual Meeting in October 2018? Come to my talk on Tuesday, October 9 to see the results of the species distribution model.

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