Tuesday, September 16, 2008

The Disappearing Eastern Spotted Skunk

There are few more interesting inclusions into the Kansas Threatened and Endangered species list than the Eastern Spotted Skunk (Spilogale putorius). The species is known by various names (e.g., polecat, civet cat) that indicate its distinction from its more common cousin skunks (the Latin name essentially means “stinking spotted weasel”). Where striped skunks (Mephitis mephitis) are more barrel-shaped and hefty, the spotted skunk is more weasel-like in appearance and small. A host of exceedingly detailed characteristics are used to distinguish S. putorius from S. gracilis (the Western Spotted Skunk), but hardly anyone honestly believed they were separate species until it was revealed that S. putorius breeds in Spring and has babies early summer, while S. gracilis breeds in the fall and has babies the following spring (Verts et al. 2001). Like all other skunks, the spotted skunk does have the skink-emitting, anal-scent glands so characteristic of skunks in general. In fact, Johnson (1921; described in Butfiloski and Swaygnham ), the spotted skunk will actually stand up on its front legs to more effectively direct its anal sacs towards a potential threat. I wish I could find a video of this behavior, but I did find a photograph (from Kinlaw 1995).

Both striped and spotted skunks have a long history as important furbearers. From the 1920s-1930s the spotted skunk was the third most harvested species in the Kansas fur-trade, averaging around 100,000 pelts a year (a level apparently believed to be sustainable), which was 3rd behind the striped skunk and possums (Roy 1997). The skunk appears to be a historic resident of Kansas, and most of the Great Plains, but some authors (e.g., Choate et al. 1973) have speculated that other spotted skunk species (i.e., the western Spotted Skunk, S. gracilis) may account for sightings prior to the agricultural settling of Kansas. In general these accounts refer to the spotted skunk as common throughout the state, even more common than striped skunks in some areas, up until about the early 1940s (Nilz and Fink 2008).

The late 30s/early 40s saw the number of skunk pelts declining significantly. By 1977 the season on these skunks was permanently closed and in 1982 the species was listed as threatened by KDWP. This wasn’t a uniquely Kansas phenomenon. Declines also occurred throughout the lower Midwest (Arkansas, Iowa, Missouri, Nebraska, Oklahoma; summarized in Nilz and Fink 2008) and potentially elsewhere in the species’ range (Reed and Kennedy 2000).

The skunk feeds on all kinds of small mammals, arthropods, birds and plant matter and is generally considered an opportunistic omnivore that benefits agriculture by eating rodents. There’s been some suggestions that the skunk moved west with agriculture and attained high densities only when benefiting from old, relatively wasteful, agricultural practices. The advent of modern farming, with less waste, chemical methods to control pests (rodents) and less ‘fringe’ habitats seems to correspond to the decline of the species. As a result, modern agricultural practices are generally considered to be at the heart of the skunk’s decline.

And decline is the right word. The spotted skunk’s preferred habitat is…just about anything native. According to the available data (which is admittedly scarce), the skunk does well in woodlands, prairies, riparian areas, scrub-land, and around abandoned farmhouses. Yet despite the huge range of habitats and food options available to the skunk, it’s almost totally absent from the Kansas landscape. Almost all the recent data comes from road kills and trappers. Nilz and Fink (2008) summarized the recent data and demonstrated that the distribution of the known occurrences of this species has continued to decline in the last thirty years. Almost nobody I’ve ever met has even seen one.

There’s a lot more out there to talk about, for instance, quite a bit is known about the evolutionary origins of this species. And apparently the skunks are in the same family as ‘stink badgers’, which I’d never known even existed. Unfortunately, I’m out of time for this week.

Choate, J.R., E.D. Fleharty, and R.J. Little. 1973. Status of the spotted skunk, Spilogale putorius, in Kansas. Transactions of the Kansas Academy of Science 76:226-233.

Johnson, C.E. 1921. The “hand-stand” habit of the spotted skunk. Journal of Mammology 2:87-89.

Kinlaw, A. 1995. Spilogale putorius. Mammalian Species 511:1-7.

Nilz, S.K. and E.J. Finck. 2008. Proposed recovery plan for the Eastern Spotted Skunk (Spilogale putorius) in Kansas. KDWP.

Reed, A.W. and M.L. Kennedy. 2000. Conservation status of the Eastern Spotted Skunk Spilogale putorius in the Appalachian Mountains of Tennessee. American Midland Naturalist 144:133-138.

Roy, C.C. 1997. 1995-1996 Kansas furbearer surveys and investigations project summary. Kansas Department of Wildlife and Parks, Unpublished report, 70 pp.

Verts, B.J., N. Leslie, and A. Kinlaw. 2001. Spilogale gracilis. Mammalian Species: 674:1-10.

No comments: