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DNR scientists are conducting a study to learn more about black bear cub survival rates, litter frequencies and litter sizes, which will be used to improve population estimates for the species. / Photo Credit: Wisconsin DNR
MADISON, Wis. – The Wisconsin Department of Natural Resources (DNR) encourages the public to report any black bear den locations across Wisconsin to help with an ongoing study on black bear reproduction in Wisconsin.
The Black Bear Litter and Diet Survey, now entering its third year of data collection, will generate updated estimates of black bear reproductive rates within each of the state's bear management zones. These updated estimates will improve the accuracy of the population models used in each zone.
Additionally, researchers are investigating a possible connection between the consumption of human food by bears and bear reproduction success, as diet can affect cub survival rates and litter sizes.
"The reports we receive from the public are an essential piece of this project," said Dr. Jennifer Price Tack, DNR Large Carnivore and Elk Research Scientist. "Obviously, people don't find bear dens every day, so it is important that people report them to us when they find them. Den reports help us meet sample size requirements for the study, which will increase the accuracy of black bear population estimates."
The public is encouraged to report as much information about occupied black bear dens as possible without approaching or disturbing the dens. Helpful information to report to the bear research team includes:
GPS coordinates of the den
Photos of the den, ideally showing it relative to its surroundings, from a safe distance (approximately 30 yards)
Description of the den site and surrounding area, including landmarks
Any information on the bear(s) and bear activity near the site
After reports are filed, Price Tack and her team will work with den reporters and landowners to visit the sites and determine if the dens are safe, accessible and active prior to any decision to survey. The research team may be unable to visit every reported den location this season. Dens that are known to be currently occupied will be prioritized.
What Data Will Be Collected
As part of each survey, DNR staff will collect biological data from these dens, including sex, weight and body measurements. Mother bears, known as sows, will be outfitted with GPS collars. These collars help staff learn more about bear foraging behavior and locate the sows in the following years for continued study. Revisiting the sows will help staff monitor the reproductive success of each sow, including her litter frequency, litter size and the survival rates of her cubs. Data on sow weight, body measurements and age are also collected.
While surveying, bear health and safety are a top priority. Designated staff monitor the sow's breathing and heart rate while the rest of the team gathers the needed samples and measurements as quickly as possible. Any cubs present at the den are carefully weighed and sexed. Cubs are tucked into staff's coats to keep them warm because the cubs cannot yet regulate their temperature. Once researchers finish collecting samples and fitting the GPS collar, the sow and cubs are returned to their den.
Looking Ahead
The Black Bear Litter and Diet Survey team will continue to survey dens for the next six to seven years. Over that time, the research team hopes to place tracking collars on at least 100 sows across the state's bear management zones, with approximately 20 collars per zone.
Thus far, the team is on pace to achieve their sample-size target, but they will need new reports each year to meet their benchmark.
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