Controversy centers on grizzly bear countby Kelsey Dayton
— April 1, 2014
How grizzly bears are counted and what the population number actually is and what it’s doing (growing, declining or remaining stable) is a matter of contention as efforts move forward to remove the animals from the Endangered Species list.
Frank van Manen, leader of the Interagency Grizzly Bear Study Team, presented a rebuttal of a 2013 report that questioned methods and findings about grizzly populations, to the Yellowstone Ecosystem Subcommittee of the Interagency Grizzly Bear Committee at its meeting in Jackson last week.
The paper, written by Daniel Doak and Kerry Cutler and published in Conservation Letters, re-examined data sets suggesting increases in the greater Yellowstone’s grizzly population. It concluded bear numbers likely increased far less than believed and that increasing observation efforts influenced the population’s trajectory. It also suggests that analysis isn’t accurate enough to allow firm conclusions about the dynamics or status of the population.
The grizzly bear study team reports a population of about 740 bears in the Greater Yellowstone, and population growth that is growing at zero (stable) to 2 percent. It also reported that 2013 saw a record number of females, 58, with cubs-of-the-year.
The Doak and Cutler report noted that flight hours for counting bears increased.
“We don’t disagree that flight hours increased,” van Manen said. “They did. The reason is that our search area expanded substantially and the reason for that is we had to keep up with an expanding population.”
Grizzly bear range increased 38 percent from 2004 to 2010. Yet bear numbers have not decreased in the core area, which researchers have flown for years for population counts.
Van Manen said the rebuttal used the same simulations of Doak and Cutler and only reaffirmed the study team’s belief that the population is estimated conservatively, and it is stable or growing. Almost 60 percent of bears that are captured in the ecosystem each year have never been caught before.
“Now how is that possible if this population is declining,” van Manen said.
The Doak and Cutler paper also said the study team didn’t account for senescence, or aging, on survival and reproduction.
Van Manen said Doak and Cutler showed animals dying at 20, which is not typical of the bears. Its equivalent to saying once a human reaches retirement age they have no chance of survival, van Manen said. Bears can live to be older than 30 years, and in the Greater Yellowstone at least one bear reached 31-years old, van Manen said. Females have been documented to reproduce as old as 25 to 27 years old, he said.
Overall, the evaluation of Doak and Cutler’s work proved the bear population is increasing and stable, van Manen said. The rebuttal also was published in Conservation Letters. In recovery zone flyovers that have been tracked consistently since 1997, bear sightings have increased from one per hour to three per hour. While those observations aren’t enough to make management decisions, it another example of the increase in population.
Doak said he is working on a response, which is planned for publication in about a month, and declined to comment until his paper is published.
Christine Wilcox, research scientist with the Natural Resources Defense Council, charges that the study team isn’t answering crucial questions about grizzly bear populations, and instead is focused on discrediting Doak and Cutler.
As for van Manen’s claim that 60 percent new captures each year means the population must be growing, Wilcox says she isn’t so sure. The bears could be using the landscape differently, especially if they are switching food sources with the decrease in whitebark pine. She claims Van Manen’s response didn’t take into account senescence, and said it didn’t have an impact. The lack of transparency is worrisome, Wilcox said.
Scientists, including Doak, have requested the study team’s data and were denied. Years ago it was said the data, which includes where the bears are, could put the animals in jeopardy. But if there are actually close to 1,000 bears, other scientists knowing where the bears are shouldn’t threaten the population, Wilcox said. Right now it’s easy for the study team to discredit any objections because they hold all the data, she said. It also makes it feel like there is something in the data the study team doesn’t want the general public to know.
Van Manen said population data is available in the annual report, on the study team website and in papers published in peer-reviewed journals. Anyone can use that data to replicate analyses for population estimates – that is what Doak and Cutler did for their paper, he said. There is also protocol for sharing data with collaborators. The study team is transparent about the entire scientific process by pointing out the limitations and caveats about the data and analyses, inviting experts to review and critique methods and collaborating with academic institutions, he said.
The U.S. Fish and Wildlife Services is conducting a threat analysis, which is expected to be finished in the fall, Chris Servheen, U.S. Fish and Wildlife Service’s grizzly bear recovery coordinator. The analysis evaluates threats to habitat from disease and man-made or other factors that could impact the continued existence of the species. The analysis is a requirement before removing the animals from the Endangered Species list.
While Wilcox said she felt like the delisting process was being rushed, she was hopeful that a thoughtful analysis would answer outstanding questions, like how the bears are using the landscape differently. She added that taking time during the threat analysis could lead to a “really solid and amazing delisting rule.”
— “Peaks to Plains” is a blog focusing on Wyoming’s outdoors and communities. Kelsey Dayton is a freelancer and the editor of Outdoors Unlimited, the magazine of the Outdoor Writers Association of America. She has worked as a reporter for the Gillette News-Record, Jackson Hole News&Guide and the Casper Star Tribune. Contact Kelsey at email@example.com. Follow her on twitter: @Kelsey_Dayton
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