Adventure Journal Feature

What You Don’t Know About Animal Bones… And Why It Matters

By Aaron Teasdale, Guest Writer, 5-16-11

Anybody who’s spent much time tromping around uncivilized places — i.e. hikers, climbers, mountain bikers, and pretty much anyone reading this site — has come across bones and skulls. PETA members and soccer moms might find this disturbing, to others it might be rad, but there’s no denying that it’s wild out there and critters are dying all over the place. Now it turns out their skulls, and whatever other bits they leave behind, still have something to say.

Biologist Joshua Miller of Wright State University in Dayton, Ohio, has spent the last few years combing the backcountry of Yellowstone National Park looking at over 20,000 bones for clues to the region’s ecological past. Humans have drastically impacted wildlife populations in recent centuries, but wildlife biologists have only been paying close attention for a few decades, so when Yellowstone wildlife managers talk about maintaining native species at pre-European settlement numbers, a commonly cited goal, they need some way to know what the heck those numbers were.

Enter Miller and his park survey. By studiously documenting what scientists call “death assemblages,” he says he has been able to “extend our ability to document long-term changes in ecological communities.” In other words, he can see what animals used to live in the park, what ones didn’t and make good guesses about how many there were by the number of bones, er, “death assemblages” he found.

For instance, horse bones were all over the place, even though Yellowstone hosts no wild horses. Radiocarbon dating showed the bones originated in the late 1800s, before cars were invented and the park was managed by the cavalry. Though there are 4,000 bison in the park, the relative lack of bison bones is easily explained by the fact that there were less than 50 in 1902, after they were nearly hunted to extinction across the American West.

It’s in this way that bones on the landscape can help wildlife scientists understand the past. Just because animals are in a place now doesn’t mean they were there 100 years ago. Mountain goats may currently live in the park’s northern mountains, but Miller’s study turned up few of their bones. Turns out they’re actually an exotic species in Yellowstone. Introduced into nearby mountains in the 1940s and 1950s for sport hunting, they’ve since sauntered into the park in the last few decades and made themselves at home in the high peaks.

And they aren’t necessarily an animal that Yellowstone can naturally support. While hikers and climbers always enjoy seeing the snow-white goats in the peaks — nothing says you’re really getting high like seeing mountain goats — there’s concern over their impact on alpine vegetation. And they compete for terrain with the actual native ruminant, bighorn sheep, a slightly less badass species.

If there’s any take away for the larger outdoor community it’s that perhaps what you think of as a constant — whether it’s the presence of bison or trout or mountain goats — is just a momentary snapshot. Species are always in flux, not just from human pressures, but from dozens of factors wildlife even brings upon itself.

Also, when you see a pile of bones in the woods, make sure to leave them there. A fellow named Joshua Miller might come looking for them someday.

This environmental coverage is made possible through Patagonia. It first appeared on Adventure Journal and is republished here with permission.

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