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Smile! Less-costly method uses remote cameras to count grizzlies

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Business guru Peter Drucker’s axiom that “you can’t manage what you can’t measure” hits a real challenge when counting grizzly bears.

Nailing the number of Ursus arctos pooping in the woods often involves lengthy searches for that poop, followed by expensive DNA analysis to identify the bear from which it came.

A much more cost-effective method of snagging hair samples developed by U.S. Geological Survey biologist Kate Kendall nevertheless earned a broadside from Sen. John McCain during his 2008 presidential campaign. The Republican from Arizona jabbed that taxpayers were spending $3 million on bear hair, saying, “I don't know if it was a paternity issue or criminal, but it was a waste of money.”

What it was, and what McCain has since acknowledged, was a reliable way to determine how many bears live in remote places like the Cabinet Mountains or Bob Marshall wilderness areas. Bear managers use that number to calculate population growth. And population growth or decline underpins all the debate around delisting grizzly bears in Montana, Idaho and Wyoming.

Interior Secretary Ryan Zinke’s announcement last week that grizzly bears in the Greater Yellowstone Ecosystem could be removed from federal Endangered Species Act protection within a month was based on biological estimates showing bears in and around Yellowstone National Park have reached sufficient numbers to sustain a viable population — provided humans don’t kill too many of them. State wildlife managers in Montana, Idaho and Wyoming would have authority to set hunting seasons and rules for killing grizzlies that attack livestock or menace people.

Those policies all depend on knowing how many bears live in those woods. And shortly before Zinke made his announcement, researchers in Canada and Missoula announced a new and improved way of conducting that census.

“Any time we can conduct our surveys more efficiently or for less money, it helps everybody,” said Jesse Whittington, a wildlife ecologist for Parks Canada and lead author of the study. “It’s challenging for wildlife ecologists around the world to monitor wildlife populations, especially in remote wilderness areas. To collect hair or scat samples, extract the DNA, and identify individuals is labor-intensive and expensive. For our study area, it would cost about $500,000. Larger areas have cost millions. And then you have to repeat the survey several times during the summer, estimate detection probability and how many animals you missed.”

Whittington, University of Montana wildlife biologist Mark Hebblewhite and University of Georgia researcher Richard Chandler published a new version of an old statistical technique called “mark-recapture” that takes advantage of the booming possibilities of remote game cameras.

A greatly simplified version of the math works like this: You have a place with an unknown number of bears, like the Bob Marshall Wilderness Complex. You can identify a few bears living there, perhaps by using Kendall’s hair snares that pluck a bit of fur from each grizzly that comes to scratch on the barbed-wire-strung tree. Using DNA analysis, you can name every individual bear that scratched on that rub tree.

Say you find 100 individual bears in the hair samples. Then you clean the snares and sample the rub tree again. Only 10 of your previously identified bears shows up in the new sample. You can estimate that your sampled bears make up one tenth of the total, unknown population. One hundred times 10 equals 1,000 — the approximate total number of bears in the Bob Marshall.

The real statistical process of mark-recapture census uses a lot more complicated math, and has been around for about a century. The new research paper takes that tool and shows how it can be reached by different, cheaper means than plucking bear hair.

The Banff-Yoho national park region was radio-collaring 22 grizzly bears to learn how to keep them from dying near railroad tracks — a frequent cause of death for Canadian bears. Whittington and his colleagues set up 214 remote cameras on overpasses, underpasses and trails throughout the backcountry. They got more than 2,000 pictures of collared and uncollared bears over three years. Using the mark-recaputure statistics with the photo collection, he got results virtually identical to the more costly DNA analysis.

The new technique also fixes a sampling error that tended to skew the results toward under-estimating the correct population.

“Where you capture the animals influences subsequent recapture,” Hebblewhite said. “In Montana, bears are usually collared in areas of high human influence.”

In the Canadian study, calculating the number of bears physically captured and re-captured by traditional methods would have indicated the population had declined by 51 percent. That’s because traps can only be set in some places, while grizzlies may wander their whole range. The trap-site data wasn’t representing the true random mix of bears moving through the backcountry, and therefore seeing a limited picture of the population.

“We combined the radio-collar process with detection by remote cameras,” Whittington said. “The remote cameras pick up lots of collared bears and unmarked bears. With that data, we’re able to obtain accurate estimates.”

Additionally, lots of researchers have collared or ear-tagged or otherwise identified lots of critters. And their colleagues have placed lots of remote cameras, for various studies. The new mark-recapture technique can get overlayed on any of those studies to add new population figures to the results.

“This paper focused on grizzlies, but we use remote cameras to monitor all kinds of wildlife populations,” Whittington said. “We can look at the distributions of lynx and wolverine and other large mammals. And we can estimate the size of populations with minimal extra costs.”

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