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Bear hunters reminded to submit rib bones for population study

From Wisconsin Department of Natural Resources

-- Wildlife researchers are asking successful black bear hunters to provide a section of rib bone from their bear for analysis as part of an ongoing black bear population survey.

The most recent three-year project to develop a second Wisconsin bear population estimate is based upon a mark-recapture technique. The first estimate was initiated in 2006 and completed in 2008 as part of a cooperative research effort between the Department of Natural Resources, University of Wisconsin-Madison and the Wisconsin Bear Hunters Association.

This second mark-recapture estimate will estimate the size of the bear population across its primary range in the northern and central parts of the state. The first phase of the current project, the marking phase, has been completed.

Results of a similar survey were reported in 2008. This second round of sample collection is being done to support and verify the findings of the first study, which showed Wisconsinís black bear population to be larger than previous surveys, using different techniques, had suggested. Results can be read at

A primary component of the marking phase was the deployment of food baits in April and May, according to bear researcher Dave MacFarland. ìThe baits consisted of peanut butter and marshmallows mixed with tetracycline, a compound that is detectable in bone tissue. These baits were placed in wooden boxes that were constructed and donated by the Wisconsin Bear Hunters Association. The boxes are accessible by bears and are designed to discourage use by other animals.î

More than 600 volunteers and DNR staff deployed and monitored 3,317 baits across 32 counties this spring, 940 of which were consumed by bears. Each consumed bait results in a marked bear as the tetracycline leaves a telltale ring visible in a cross section of the rib bone.

The population estimation project is now entering the critical second phase, the collection of rib samples from successful bear hunters. Ribs will be analyzed to look for tetracycline exposure. The resulting data are incorporated into population models to estimate the number of bears in the state. Good participation from hunters is critical to the studies success.

Sample collection materials and instructions were provided to hunters who received Class A bear permits. Rib samples should be collected near the vertebrae, cleaned of all soft tissue, placed in the baggie provided and submitted to the registration station. Hunters can also mail their rib sample directly to Dave MacFarland, Wisconsin DNR, 107 Sutliff Ave, Rhinelander, WI 54501.

Phase three of the project will be a second year of rib sampling from the 2012 bear harvest to maximize the recapture of marked bears. The laboratory analysis of the ribs will be completed during winter 2012-13 and final a population estimate will be calculated.

When completed, the population estimate will calculate the size of the bear population for the surveyed area as of September of 2011.

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