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Preliminary results of a two-year cooperative study of Wisconsin black bears suggest that the population may be two times or more larger than currently thought. Biologists stress that the new estimate comes from a half finished study and may change when data from the second year of the study are analyzed. Early results are encouraging, however, and indicate Wisconsin continues to provide quality habitat for large mammals like bears.
"This is good news," said Keith Warnke, Department of Natural Resources deer and bear ecologist. "It means we have a healthy bear population, and we may be able to expand bear hunting opportunity. The other good news is that more people will have opportunities to see these great animals in the wild."
The two-year, DNR-funded study was conducted by University of Wisconsin-Madison Wildlife Ecology graduate student Dave MacFarland under the guidance of Dr. Timothy Van Deelen.
"The preliminary results are comparable to bear densities in Minnesota and Michigan's Upper Peninsula," said Van Deelen. "Dave and I spent a good deal of time rechecking our calculations and we're eager to see if the results hold when the second year of data are incorporated."
In the bear study, some 3,500 baits marked with tetracycline were set out across the state's bear range in 2006. Tetracycline, when ingested, is harmless to bears but leaves a telltale line in a bear's bones. Successful bear hunters in 2006 and 2007 were asked to provide a section of a rib bone from bears they harvested for analysis. From those samples, the biologists were able to use a formula to calculate the estimated bear population.
Using tetracycline is a variation on a wildlife population estimating technique known as mark and recapture. Other examples of mark and recapture are banding of waterfowl and songbirds and radio collars or radio implants on other species. When hunters report harvesting a banded game bird or biologists recapture a banded songbird, that information is used in a model to estimate total populations.
Currently, biologists track black bear populations by placing a series of baits on routes in each county throughout the black bear's range and record which are consumed by bears over a week long observation period. Biologists use these observations to help build a population model that also takes into account hunter harvest, hunter success rates, bear population data and historical harvest rates to generate a population estimate. This model estimates the current black bear population in Wisconsin to be at about 13,000.
"It is important to keep in mind that these models both provide information for us to consider when managing the bear population, and both are important to scientific bear management," Warnke said. "We are always working to improve the science we have to manage wildlife populations. The department funded the research to improve our bear population estimate and expand the science base we have on this species. The Wisconsin Bear Hunters Association was a key collaborator on this study and many members participated in gathering data and contributing research supplies. I'd also like to thank Dave MacFarland for organizing and conducting this research and his help in enlisting cooperation from the bear hunters."
In the tetracycline study, a much larger number of bait stations were used and the bait stations were constructed in a way that only bears could reach the bait. The new study also carefully adjusted the amount of bait so that a single bear would likely consume all of it in one visit, greatly reducing the possibility that one bait might mark two bears. By comparing the number of baits consumed in a season to the number of harvested bears showing the tetracycline marker in their bones, scientists were able to calculate the new population estimate.
Officials stress that these are preliminary findings and it is too early to draw conclusions or implement changes. The earliest possible changes that would impact bear hunting permit availability would be for the 2009 hunting season. Adjusting black bear population goals will necessitate changes to administrative rules and involve public meetings, and Natural Resources Board and legislative approval.
"When the final results are in we'll be able to use this information to assess bear population goals and adapt our bear management program," says Warnke. "Any changes to bear management policies will be done carefully, with public input and only after thorough analysis of potential impacts. The first priority is and always will be conservation of the resource."
"Our bear population is expanding and one benefit of that is that people can expect to see bears in areas outside what is thought of as traditional range," Warnke said. "Despite bears' general shyness toward humans, people in the central and southwest areas of the state likely can expect to see more evidence of bears as they disperse, looking for new territories."
Adult black bears typically weigh 250 to 500 pounds for males (boars) and 200 to 450 pounds for females (sows). Infant bears, called cubs, are born quite tiny but by the time they are 2 months old, they weigh about 6 pounds. Females give birth to two or three cubs in January or February when they are still in their winter sleep. When standing on all four paws, adult bears measure 2 to 3 feet tall at their shoulders.
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