Magnum Opus 

Be on the lookout for this Montana slime

They're all special in their own way: Magnum P.I., a .357 Magnum, a magnum of champagne, a magnum ... mantleslug?

The first three are large and impressive; the last one, not so much, at least at first glance. Even within the realm of slugdom, the species doesn't hold a candle to the banana-sized garden slugs that mow down marigolds and leave slime trails all over patios in more temperate places. Yet in our corner of the world, Magnipelta mycophaga does stand out.

The magnum mantleslug—amushroom-eater, as its scientific namesuggests—is the largest of Montana's nine native slug species. But it's discrete for a celebrity.

As the name also implies, these slugs can get big—for its kind—or up to 3 inches fully extended. The mantle refers to the thicker, cloak-like part on its back that covers its flexible internal shell (snails have external shells; slugs do not), in this case extending about two-thirds of its length. While I had hoped that this magnum might be all twinkly-eyed and mustachioed, it actually looks more like something I might find rotting in my refrigerator vegetable drawer.

The creatures resemble "an unusual lump of dirt or decaying vegetation," says Paul Hendricks, a zoologist with the Montana Natural Heritage Program and the author of a forthcoming Guide to Land Snails and Slugs of Montana. They're described much more poetically by Canadian artist and naturalist Aleta Karstad on her website: "Its richly mottled mantle is like a cape, and its body beneath like pleated gray skirts—a most elegant slug."

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Also known as the Idaho-Montana slug or the spotted slug, the mollusks are a regionally endemic species—you don't find them anywhere else, Hendricks notes. They've survived in the pockets of habitat left over after connections to the wetter forests of the Cascade Mountains were cut off during the Pleistocene Epoch and earlier. As far as anyone knows, they exist only in northwest Montana, northern Idaho, southeastern British Columbia and extreme northeastern Washington.

Yet despite being studied in the 1950s by University of Montana professor Royal Bruce Brunson and Philadelphia's Henry Pilsbry, the "grandmaster" of North American land mollusks, not very much is known about them. What do they eat and what eats them? What does their life cycle look like? How many exist, and where?

For this reason, and because their habitat seems so restricted, magnum mantleslugs are a state species of concern. (The Montana Natural Heritage Program would be happy to hear if you should find any.)

Hendricks says they're chiefly found in moist, forested areas, munching away on fungus and green vegetation, one of the army of decomposers that nutrient recycling depends on. He's discovered them in mature and old-growth stands of western red cedar, grand fir and western hemlock, but he's also come across them in unburned patches of subalpine fir and lodgepole pine in the Sapphire Mountains, and along various creeks.

They hide in the coldest months, hibernating in or under pieces of downed wood. A better time to seek them will be this spring and next fall, when they are more apt to be out doing their slug-y things, like poking around in search of hermaphroditic rendezvous. (Slugs have both male and female reproductive organs, but that doesn't stop them from mixing it up like other species.)

Hendricks says he once found about 30 magnum mantleslugs in an hour of searching along the west fork of Petty Creek in May, and has observed some mating during that time as well. Perhaps this is when they pull out the tiny red Ferraris and start waving the bubbly.

Among all the magnums—guns, TV detectives and booze—mantleslugs are certainly the meekest. They might not be inheriting the earth, but they've done well enough eating it. What makes them of particular interest otherwise is hard to say. Though perhaps lacking the charisma of Tom Selleck, to me they are rare creatures, vestiges of an earlier landscape, a story of evolutionary survival, pieces of the diversity puzzle. Now that they're on my radar, I'll pay a little more attention to dirt clumps along the trail, and hope that some might turn out to be alive.

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