Tree Size Influences Habitat Recovery for Endangered Indiana Bats, Study Reveals

On July 1, 2026, researchers from Minot State University and the University of Illinois at Urbana-Champaign discovered that tree size, rather than age, is crucial for the habitat recovery of endangered Indiana bats (Myotis sodalis). The study, published in Forest Ecology and Management, provides vital insights for forest management aimed at preserving this federally endangered species.

Importance of Tree Size for Indiana Bats

The research highlights that tree size, specifically diameter, is the primary factor in determining suitable roosts for Indiana bats. Lead author Joseph Pettit, an associate professor at Minot State University, stated, "Diameter predicts which trees house the most bats. We've known that for a long time. Our question was specifically, 'How can we quickly get to that diameter?' And the answer is early-successional trees." This finding suggests that forest managers can expedite the creation of roosts by focusing on faster-growing tree species.

According to Pettit, while typically it takes about 100 years for a tree to reach roost size, early-successional trees can become viable for bats in as little as 70 years. Conversely, late-successional trees usually take around 130 years to mature. These early-successional trees, which thrive in open sunlight, are essential for swift habitat recovery.

Combining Tree Types for Effective Management

Both early-successional and late-successional trees play critical roles in maintaining habitats for Indiana bats. Co-author Joy O'Keefe, a wildlife extension specialist, emphasized, "A smart management approach recognizes the importance of maintaining a combination of early-successional and late-successional trees. Each provides a unique benefit that is necessary to create consistent habitats for the bats." This balanced approach ensures that both types of trees are available to support bat populations.

The team conducted extensive fieldwork, radiotagging bats and tracking them to their roosts across three sites: central Indiana, the Great Swamp National Wildlife Refuge in New Jersey, and the southern Appalachian Mountains. The study utilized dendrochronology to analyze the age of the trees, revealing that the oldest late-successional tree surveyed was around 250 years old.

Management Implications for Forest Habitats

Typically, Indiana bats prefer to roost in standing dead trees, known as snags, which begin to split about four years after death, creating ideal roosting spaces. The research found that late-successional trees stand for an average of 12 years post-death, while early-successional trees tend to fall within 8 years. This highlights the need for ongoing forest management to ensure a consistent supply of roosts.

Forest managers are advised to create new suitable roosts every three to four years to maintain a stable habitat for the Indiana bats. The study underscores the importance of planning decades ahead, as it is imperative to grow large trees that do not need to be immensely old to provide shelter for these endangered bats.

"If our goal is to be able to design and create good habitats for this endangered species, it is amazing that age is not the main predictor of how many bats roost in a tree," said Pettit. "It means that we can grow big trees that do not need to be immensely old."