Lake Vermillion After Dark
“We wanted to find out if there were any significant bat colonies, especially Threatened or Endangered species, using those islands,” says BCI Senior Restoration Specialist Dan Taylor.
The work, commissioned by the Bureau of Land Management (BLM), focused on a chain of small, federally managed islands scattered across Lake Vermilion. The islands have mature trees, minimal disturbance, and just enough isolation to make them intriguing as potential bat habitat. More than 300 islands are located within the 30-mile-long lake.
To find out what animals were flying after dark, BCI turned to acoustic monitoring. Over three days in May 2025, Taylor and his team installed five recording stations, each mounted atop a 15-foot pole and aimed toward small forest openings on selected islands.
The detectors recorded nightly from spring through early fall, capturing bat echolocation calls from dusk to dawn for one week each month. This setup provided a low-impact way to monitor wildlife in places that are otherwise difficult to study.
By late summer, the data told a clear story: Bats were using the islands, but not necessarily the species that researchers expected.
Across 175 nights of recording, the team detected five species: little brown myotis (Myotis lucifugus), silver-haired bats (Lasionycteris noctivagans), big brown bats (Eptesicus fuscus), eastern red bats (Lasiurus borealis), and hoary bats (Lasiurus cinereus). “The most frequently recorded bat was the little brown myotis, and that bat has experienced 90% declines across much of its range,” Taylor says.
The finding was both encouraging and surprising. Once one of the most widespread bats in North America, the little brown myotis has been devastated by white-nose syndrome, a fungal disease that has wiped out entire colonies. Its strong presence on Lake Vermilion suggests the area may still provide important summer foraging habitat, especially over water, where insects are abundant.
Migratory bats like silver-haired and eastern red bats appeared regularly, likely passing through or feeding along the lake’s edge.
“There are migratory bats that we expected,” Taylor says. “They fly long distances, so you would expect to get them coming through.”
Two species of particular concern, however, were notably absent: federally Endangered northern long-eared bats (Myotis septentrionalis) and declining tricolored bats (Perimyotis subflavus), which were key targets of the study. Combined with habitat data, their absence suggests the small islands, lacking large interior forests and suitable roost trees, may be less important for those species than the mainland.
Encouraged by the results, BLM has already asked BCI to expand monitoring to a much larger site nearby. On a lake defined by its many islands, the next chapter of discovery is already taking shape, one night call at a time.