Michigan bat populations remain low despite stabilization efforts

Michigan Department of Natural Resources biologists report that bat populations across the state remain significantly reduced following the arrival of white-nose syndrome, a fungal disease that has decimated hibernating colonies since 2014. While the little brown bat population has begun to stabilize at low levels, the northern long-eared bat continues to decline, now accounting for less than 1% of the state's bat population.

Researchers documented fewer than 800 bats per cave annually since 2015, a sharp drop from the nearly 2,000 recorded per site before the disease emerged. During the 2025-26 winter season, DNR teams surveyed 24 sites in the Upper Peninsula and recorded an average of 510 bats per cave, with some locations previously hosting tens of thousands of animals now holding only a few thousand.

The decline has broader ecological and economic implications, as bats consume millions of insects nightly, saving farmers billions in crop damage and pesticide costs. A 2024 study linked the loss of bat populations to a 31% increase in insecticide use and a nearly 8% rise in infant mortality rates in affected U.S. Counties, highlighting the critical role these animals play in the ecosystem.

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