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Did you know Massachusetts has one of the longest running black bear research projects in the region? For the last 40 years, MassWildlife biologists, graduate students, and researchers have been using radio tracking collars to collect essential information from female black bears, known as sows. As of today, MassWildlife has 39 sows in Massachusetts fitted with radio tracking collars. These collars provide data about sow survival, reproduction rates, and cub survival. Thanks to funding from the Massachusetts Department of Transportation (MassDOT), about half of the collars have GPS units that track bear movement and habitat use. This data helps MassWildlife and MassDOT improve habitat connectivity and minimize road impacts on bears and other wildlife. All of this information is critical to understanding our growing and expanding black bear population.
Winter Den Research
As part of this project, MassWildlife biologists visit the dens of collared sows during the winter. Sows may be in their dens alone, with newborn cubs, or with their previous winter’s cubs, called yearlings. Winter dens can be a hollow tree or log, rock crevice, or a ground nest under fallen trees or brush. Once they locate the den, biologists carefully immobilize the sow. When working with the sow, the team documents her body condition and weight. They also evaluate her collar for proper fit and function. If the female has newborn cubs, the cubs are counted, weighed, sexed, and kept warm until they’re returned to the den. If the female has yearlings, the yearlings are immobilized while biologists document the number of yearlings, their body condition, their sex, and their weight. Some female yearlings are fitted with an expandable radio tracking collar to add new bears to the study.
2024 Bear Den Season Summary
This winter, MassWildlife biologists visited 30 dens. A summary from this winter’s study includes:
A challenging factor during this year’s den season was the mild winter. While most black bears den for about 5 months without eating, drinking, or excreting waste, they can easily awaken, especially if temperatures are unseasonably warm. Given the string of warm days in early March, there were several signs that even sows with newborn cubs were active earlier than usual when they’re typically the last to emerge from their dens. If average temperatures continue to rise and New England seasons become less distinct, we could see non-pregnant black bears more active throughout the winter and some may forgo denning completely, which is common further south. This could cause an increase in human-bear conflict as bears would be searching for food sources year-round.
How to help black bears and prevent conflict
As bear population densities increase in central Massachusetts, and ranges expand east of I-495, it is more important than ever for people to take steps to coexist with black bears. "Please help us protect our bears and don't provide food to bears," said Dave Wattles, MassWildlife's Black Bear Project Leader. "Remove bird feeders, secure garbage, and use electric fencing to protect bees, chickens, and small livestock. When bears feed at these food sources it often ends badly for the bear."
You can help keep bears healthy and people safe by:
Learn more at mass.gov/bears
Click here to see video footage of black bear winter den research.