A deceptively simple device, coupled with the latest in DNA technology, will soon give state wildlife managers a far more accurate way of estimating bear populations – the cornerstone of managing bears and minimizing their conflicts with humans.
“We’ve known for quite some time that we’re underestimating our bear population,” said Rick Winslow, bear and cougar biologist for the New Mexico Department of Game and Fish. “But you have to have better numbers to prove that.”
Getting better numbers – particularly in areas like the Sandia Mountains where urbanization has surrounded historic bear habitat – has been a challenge.
New Mexico’s estimated bear population – between 6,000 and 7,000 – is based on a comprehensive study conducted in 2001, and computer modeling that factors in variables such as availability of food, overall bear health and reproduction and bear mortality.
Game and Fish biologists have estimated the bear population in the Sandias, which has about 136 square miles of primary bear habitat, at 46 to 72.
Using population estimates, department officials set an annual “sustainable harvest limit” – the number of bears that can be killed in a year and still maintain a sustainable bear population.
Critics, including Jan Hayes with bear advocacy organization Sandia Mountain BearWatch, contend Game and Fish’s population estimates are meaningless and that its management policies are decimating the bear population in the Sandias.
But Winslow says game managers are working hard to establish a sustainable population of healthy bears that minimizes human-bear conflicts, which arise about this time every year and last through late summer.
In the Sandias last year, 36 nuisance bears were trapped and relocated, 18 were “depredation” kills – meaning they came into dangerous or potentially dangerous contact with humans and were killed by game wardens or landowners – 10 were “road” killed and one was killed by a licensed hunter, according to Game and Fish officials.
Those numbers are offset by bear births, bears migrating from other mountains, and relocated bears that make their way back to the Sandias – a relatively common occurrence, game managers have said.
A better mousetrap
The single strand of barbed wire stretched knee-high between trees in an irregular rectangle hardly looks like cutting-edge technology. The stench emanating from the small pile of pine needles and branches inside the rectangle – either skunk essence or a mixture of fish emulsion and bovine blood – is repellent to humans, but an irresistible lure to bears.
The putrid aroma brings bears to the snares – where tiny tufts of their hair are snagged by the barbs – without the reward of food, which would likely have them returning to the site repeatedly.
The hairs are sent for DNA testing, which provides game managers with a wealth of information, including the identity of individual bears, their sex, genetic variations among bear populations, where they go and even how they are related. Over time, the data can give game managers a “much, much more accurate” estimate of bear population than what’s currently available, Winslow said.
The statewide bear-hair study, though new to the Sandias, is entering its third year, said Matt Gould, a doctoral biology student with New Mexico State University’s Applied Statistics Program. Gould said he will conclude bear data collection later this summer in the Sangre de Cristos in northern New Mexico and the Sacramento Mountains in south-central New Mexico.
Since May, Winslow and a cadre of volunteers have been setting up hair snares throughout the Sandias. Statewide, 162 of the snares have been set up, Gould said.
The Sandias have been divided into 12 separate “cells” measuring 25-square-kilometers apiece. One snare is set up in each cell.
“We put the snares in places where we think bears are most likely to be, but not too close to the snare in an adjacent cell,” Winslow said. Having snares too close together could skew data results. The snares are checked every 14 days, and hairs caught on the barbs are carefully removed, placed in collection envelopes and painstakingly cataloged.
The snares are then relocated elsewhere in the cell.
While checking snares last week near opposite ends of the 6.3-mile Piedra Lisa Trail on the western face of he Sandias, Winslow collected hair tufts from two barbs.
“These look like bear hairs, but they could be anything,” he said, noting that the area is frequented by skunks, deer, rabbits, coyotes, dogs – even humans.
Ideally, the follicle will still be attached to the hair’s base, which is where the DNA resides. The samples are sent to Wildlife Genetics International in Canada for analysis. As a cost-saving measure, “If preliminary testing shows it’s not bear DNA, they’re not to do further testing,” he said.
No hairs were found at the second snare site, so it was “refreshed” with a blood lure and left in place.
Once the DNA analyses are complete and reports developed, Game and Fish staff will make management recommendations to the governor-appointed state Game Commission. The Sandia analysis, and new population estimate, should be available by mid-2015.
Less money, more information
In the past, Game and Fish has used the 2001 bear study, field visits, partial counts and other data as a basis for bear population estimates – which Winslow readily admits are educated “guesstimates.” The department has also used radio collars to track the mobility of individual bears, which is added to the mix of knowledge that determines how they are managed.
Radio collaring, however, is expensive.
“You basically do a big ecological study – what we call collar and foller,” Winslow said. “It’s expensive and time-consuming. Now, with GPS collars, it’s better than it used to be, but those collars are considerably more expensive. We used to pay $200 for a collar; now it’s about $3,000, so you can’t put as many (collars) out” in the field.
“Using genetics techniques, you can, for a much lower cost, get the same, and more, information.” he said.
The savings is notable. For about $5,000, biologists could collar and track two bears for up to a year. That’s roughly what it would cost to genotype – or determine the genetic makeup of – 100 bear-hair samples, Winslow said.
“This (bear-hair analysis) is a much more in-depth way of studying bears, and it’s a lot cheaper than older techniques,” he said. “And you get a lot more data.”
Winslow said bear-hair studies in areas of Colorado and Arizona that are next to New Mexico bear habitats strongly suggest that Game and Fish is underestimating the bear populations in those areas by half, meaning there are probably twice as many bears there than current estimates would indicate.