Ursus Controversius, part II: Who’s Counting?

via lowjumpingfrog (Flickr Creative Commons)

“There’s a bear in the woods,” the solemn voice-over intones in this 1983 Ronald Reagan re-election ad.  “For some people, the bear is easy to see.  Others don’t see it at all.”  Reagan, of course, was referring to the perceived menace of the Soviet Union rather than the animal itself, but the expression has stuck around in political circles as a euphemism for a looming and seemingly intractable problem. But the ad’s opening words could also apply quite literally to the difficulty of counting the number of bears in U.S. forests—some see them everywhere, others aren’t so sure.  Having an accurate count is important, given that the federal government is currently considering removing Yellowstone’s once-threatened grizzlies from the Endangered Species List.  But over the past year or so, doubts have begun crept in about bear counting methodologies and the validity of the population estimates that we take at face value.

You can find part I of the Ursus Controversius series here.

Some brief history: Grizzlies once roamed the entire western half of North America, with an estimated population between 50,000 and 100,000 in the mid-1800s.  As settlers moved west, the bears were seen as expendable; ranchers and hunters killed thousands with impunity.  By the turn of the century, the bears had become one of the rarest sights in the West.  (The grizzly’s loss was the American black bear’s gain; freed of larger competition, the smaller species expanded its range into newly cleared areas and propagated far and wide.)  However, bears and humans remained at odds through much of the 20th century.  In 1975, the federal government designated the park’s 1,200 grizzlies in the country as “threatened” under the provisions of the Endangered Species Act.

Tracking bear numbers, however, was no simple task.  Bears go out of their way to avoid humans and live in some of the most densely forested wilderness in the country.  In the early days of the ESA’s implementation, there were not yet any intramuscular tranquilizers considered safe enough to fire at long-range, so researchers instead applied anesthetics by hand (after first catching the bears in leg traps).  Once an animal was subdued, the scientists attached an ear tag.  If that particular animal turned up again (dead or alive), scientists could extrapolate its movements over time.  But there was no guarantee the animal would ever be seen again.  It was, in retrospect, a crude and time-intensive process that offered frustratingly inconsistent results.

Enter radio-tracking collars.  Implemented widely during the mid-1960s, these portable transmitters were a mini-revolution.  By fastening a collar around a bear’s neck, researchers could identify an individual’s location at any given moment and keep track of its movements over its entire lifetime.  Easy to build and cheap to maintain, the so-called VHF (very high frequency) collars quickly became the go-to method for long-term wildlife research.  Combined with satellite imagery (a byproduct of the space race that trickled down to civilian usage by the early 1970s) and, more recently, GPS transponders, scientists had more tools at their disposal than ever before.

Within the last decade, scientists have begun using more non-invasive methods such as hair traps.  Researchers place scented lures inside a barbed wire perimeter that snags the bear as it enters to investigate.  The bear may be temporarily inconvenienced, but can always free itself from the barbs easily and be on its way.  Scientists then collect fur left on the wire and send it to the lab for DNA analysis.  Researchers can identify individual animals, extrapolate family information, and build a comprehensive database of bears this way.  It is, however, a field still very much in its infancy.

Such newfangled sampling methods might lead one to think that we’ve got this all figured out, that we can indeed count bears in quantitative and authoritative fashion.  But it’s never that simple.  Although North American grizzlies have almost certainly rebounded from their nadir over the past 35 years, the big question now is whether they’re, ahem, out of the woods or not.  Daniel Doak, a wildlife demographer at the University of Colorado-Boulder, caused a stir earlier this summer when he wrote a paper questioning the grizzly recovery that federal officials are eagerly touting.  According the Department of the Interior, there are around 700 grizzlies in Yellowstone, up from 600 the previous year based on a revised assumption about the number of male bears vs. female bears.  The estimate was primarily based on aerial surveys, but Doak points out that that methodology might be biased since the number of monitoring flights has more than tripled over the past two decades.  If you’re looking for bears more often, it stands to reason that you’ll see them more often.  It doesn’t necessarily mean that the population jumped 17% in a single year.

There are other problems with the government’s findings, too.  When cubs switch families (as sometimes happens), they are ripe to be double counted.  Bears have had to range farther to find food thanks to habitat loss, pushing them onto exposed rock slopes and thus making them more visible.  Doak also points out that we still don’t know enough about the reproductive cycles of mama grizzlies to know how long they stay fertile or even how many cubs they are capable of producing in a lifetime.  (Federal calculations assume a constant fertility rate throughout a female bear’s life, unlikely for any mammal).  Such assumptions make an overcount not only probable, but likely.  According to Doak and his team, the actual grizzly population may have even ticked down slightly over the past few years.

If he is correct, and there are serious flaws here, what is to be done?  One solution would be to place less emphasis on problematic aerial surveys and put more funding into the DNA-based methods, which contain more useful “metadata” such as the animal’s health and family history.  The downside is that it’s much more difficult to sample large numbers of bears and get the big picture about the animal’s geographic distribution within the park — important info for a national park that’s trying to minimize potential bear/human encounters.

It remains to be seen what the next wave of Yellowstone bear research will focus on, but Doak’s study has uncorked a controversy that could complicate the government’s plans to take the park’s grizzlies off the Endangered Species List next year.  At the very least, the study puts forth a convincing argument for caution in the near term when it comes to managing grizzlies.  There may be bears in the woods, after all, but clearly only some people are seeing them.

Trent Knoss is a digital media editor at Backpacker Magazine and lives in Boulder, Colorado.

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