Wednesday, January 8, 2014

The Secretive Spotted Skunk

Eastern Spotted Skunk
By David Jachowski

    One of the rarest and most secretive mammals in North America might be a skunk. Not your average backyard, dumpster-loving Striped Skunk (Mephitis mephitis) that causes you to hold your breath after passing an overnight road kill on your morning commute. I am talking about the smaller and perplexingly rare Spotted Skunk (Spilogale putorius). This decoratively marked forest dweller, known in Mexico as zorillo or “little fox,” is infrequently seen within the United States, though it ranges from the Channel Islands of California to the foothills of the Appalachian Mountains.

    As an example of its rarity, take a look at the central Appalachian region in Virginia and West Virginia. Despite being among the first places explored by natural historians in the “New World,” there have only been 64 confirmed sightings of Eastern Spotted Skunks in both states… ever! And this is not because these skunks are recent arrivals. Prior to being the 3rd president of the US, in 1785 Thomas Jefferson tallied “zorillos” proudly alongside the woolly mammoth (that at the time he thought still existed), bison and raccoon as one of America’s unique species in his influential natural history volume “Notes on the State of Virginia.” The first official record of an Eastern Spotted Skunk in Virginia dates back to a specimen collected in 1898 and housed in the Smithsonian Institution in Washington, D.C. Over the next 115 years, sightings have trickled in, with the species going undetected in most years and never more than 1-5 reported in any one year in Virginia.

Why is it so rarely seen? 


Biologist Damon Lesmeister with a sedated Spotted
Skunk that is about to be fitted with a radio-tracking collar
    The mystery of why Eastern Spotted Skunks are so secretive is unknown, but we can gain some insights from other parts of the U.S. The only detailed studies of Eastern Spotted Skunk behavior come out of the Ouachita Mountains of Arkansas. There, over the course of two years, biologist Damon Lesmeister captured and tracked Eastern Spotted Skunks in the wild and found that they really loved to hang out in young forests with dense understory cover. This discovery, along with observations about what was killing some of his study animals, led him to hypothesize that Eastern Spotted Skunks select this type of habitat as a defense mechanism to avoid detection by their main predator, owls. 

    The importance of avoiding predators is backed up by studies in the Channel Islands off the coast of California where the main predators of Spotted Skunks are not owls, but the Channel Island Fox (Urocyon littoralis). Here, following restoration of Golden Eagles (Aquila chrysaetos) in the mid 1990’s, Channel Island Fox populations crashed, allowing for a 10-40 fold eruption in Island Spotted Skunk numbers. In other words, the eagles ate the foxes that were predators of skunks, but they left the skunks alone. The take-home message is that we know Spotted Skunks can be victims or benefactors of complex interactions with predators higher up on the food chain, and that being hard to find is an advantage.

Have you seen a Spotted Skunk? 

    Throughout its range, we still do not really know if the species is actually in danger of extinction, or if it is just really hard to find. If it is in danger, we need know what limits its numbers and how to improve its status. In the Eastern U.S. in particular, is the skunk harmed by habitat alteration and associated depredation by owls? Or is it foxes? Might there be a disease at play?

    In an effort to learn more, I am working with colleagues at Virginia Tech to collect observations and study Eastern Spotted Skunks. Every sighting and story helps us fill in a little bit more information about this secretive and uniquely American mammal, so regardless of where you live (or have lived), we would love to hear your Spotted Skunk stories. If you live in the Appalachia region and want to become a more active part of our citizen science team, consider volunteering to set out a trail camera. More details can be found on the website www.AppalachianEagles.org.

As American as apple pie 

An Eastern Spotted Skunk doing its
signature warning handstand, often
the last line of defense before
expressing its scent glands.
    Did you know that skunks as we know them are unique to the Western Hemisphere? The word "skunk" is a variation on the Algonquin word "seganku," picked up and modified by New England colonists in the 1600's. In the Philippines, Malaysia and Indonesia, there are two skunk-like species called “stink badgers.” However, the Americas are the hotbed of skunk diversity, containing the Striped, Hooded, Hog-nosed, and Spotted Skunks. So the next time you pass a road-killed skunk, take time to identify it to species. If it is a Spotted Skunk, please send us an email. If it is a Striped Skunk, you can still hold your breath - but please don’t close your eyes to what Thomas Jefferson saw as a uniquely American trademark.

Want to Learn More? Check out these Scientific Articles:

Gompper, M.E., & Hackett, H.M. (2005). The long-term, range-wide decline of a once common carnivore: the eastern spotted skunk (Spilogale putorius).   2005, 8, 195-201 DOI: 10.1017/S1367943005001964

Jones, K.L., & et al. (2008). Sudden increase in a rare endemic carnivore: Ecology of the island spotted skunk. Journal of Mammalogy, 89, 75-86 DOI: 10.1644/07-MAMM-A-034.1

Lesmeister, D.B., & et al. (2012). Landscape ecology of eastern spotted skunk in habitats restored for red-cockaded woodpeckers Restoration Ecology, 2012, 267-275

All photos appear courtesy of Damon Lesmeister.

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