Public asked to report black bear den locations for research study

WISCONSIN – The Wisconsin Department of Natural Resources (DNR) is encouraging the public to report any black bear den locations across the state to help with an ongoing study on black bear reproduction.

In a release, the DNR said the Black Bear Litter and Diet Survey will generate new estimates of black bear reproductive rates within each of the state’s bear management zones.

“These estimates will improve the accuracy of the population models used in each zone,” the DNR stated. “Additionally, researchers are investigating a connection between consumption of human food sources and bear reproduction, since diet can affect cub survival rates and litter sizes.”

The study will be entering its fifth year of surveying occupied dens in the Wisconsin bear range. The research team will accept a den report anywhere in the state.

“However, the team is particularly interested in finding dens in bear management zones C, E and F, which cover central and southern Wisconsin,” the DNR said, noting that having collared bears in every zone will improve population estimates for each respective zone and support management decision making.

The DNR said the public’s assistance is essential to the project.

“Anyone who happens upon an occupied black bear den is encouraged to report as much information as possible without approaching or disturbing the animal,” the DNR said. “Reporting dens helps the DNR meet the sample size requirements for our study and will increase the accuracy of the black bear population estimates.”

If a black bear den is discovered, the DNR is asking the public to collect the following information quickly and quietly while remaining a safe distance of at least 30 yards from the den at all times:

• GPS coordinates. You can use a mobile phone’s pre-installed map app, such as Google Maps or Apple Maps. For best results, first go to your phone’s Settings and turn on the option to improve location accuracy.
• Photos of the den. Maintaining a safe distance, take an image or two showing the den in relation to its surroundings.
• A description of the site and surrounding area. Take some notes on the size of the entrance, the direction it faces and whether there are notable landmarks nearby.
• A description of any bear activity in the general area. Make a note of anything you observe, including paw prints, scat, fresh scratch marks and even, in late winter, the squeals and grunts of hungry cubs.

Before the research team surveys a den, they will work with the den reporters and landowners to determine whether it is safe, accessible and in use, according to the DNR. Den reporters, landowners and/or land managers are typically invited to help if there is a planned survey for the reported den. The research team may not be able to visit every reported den location this season; they will prioritize dens that are confirmed to be occupied.

The DNR said staff will collect biological data from these dens, including sex, age, weight and body measurements.

“Mother bears, or sows, will be outfitted with a GPS collar, one of the most important pieces of equipment for the study,” the DNR stated. “Collars help staff learn more about bear foraging behavior and locate the sows in the future. Revisiting the sows will help staff determine the reproductive success of each sow, such as how often she has a litter, litter size and the survival rates of the cubs.”

During a survey, bear health and safety are a top priority, the DNR noted.

“Designated staff monitor the sow’s breathing and heart rate while the rest of the team quickly gathers the needed samples and measurements,” the DNR said. “Any cubs present at the den are carefully weighed and sexed. Cubs are tucked into team members’ coats to keep them warm, because the cubs cannot yet regulate their own temperature. Once researchers finish collecting samples and fitting the GPS collar, the sow and cubs are put back into their den.”

The DNR noted that this process can be seen in a 2024 episode of PBS Wisconsin’s “Wisconsin Life” series.

To report a known black bear den, visit the DNR’s Black Bear Den submission form.