Rare bat species confirmed at Warren County reservoir, expanding known range in New Jersey

HARMONY TOWNSHIP, N.J. (Warren County) — A rare and elusive bat species has been confirmed at Merrill Creek Reservoir (MCR) in Warren County, marking the first known detection of the Eastern small-footed bat at the site—and in the county—according to a joint announcement by MCR, the Conserve Wildlife Foundation of New Jersey (CWF), and the New Jersey Division of Fish and Wildlife (NJDFW).

The discovery is part of a two-year research initiative between MCR staff, CWF, and NJDEP Fish and Wildlife’s Endangered and Nongame Species Program to survey bat populations at the reservoir and determine whether it could provide suitable habitat for Myotis leibii, commonly known as the Eastern small-footed bat.

“We’re thrilled to report the first confirmed presence of this rare species at Merrill Creek Reservoir,” the MCR team said. “It’s not only a first for the reservoir but also for Warren County.”

The Eastern small-footed bat is proposed for endangered listing in New Jersey. Its small population and unique hibernation behavior put it at high risk for white-nose syndrome, a disease that has decimated bat populations across North America.

Typically found in rocky, elevated environments with nearby water sources, the species is notoriously difficult to detect due to its elusive behavior and overlapping echolocation calls with other myotis bats. According to range data from the state’s Biotics database, sightings have historically been concentrated in parts of Sussex, Morris, Passaic, Bergen, and Somerset counties.

However, Merrill Creek Reservoir—situated in the Ridge and Valley region and constructed using large rock and talus—was flagged as a potentially ideal site for the species.

Initial acoustic surveys conducted in 2024 and 2025 picked up ultrasonic echolocation calls suggestive of Eastern small-footed bats. But due to limitations in acoustic identification, researchers followed up in July 2025 with mist-netting, a safe method of capturing bats in flight for close inspection.

During the first night of mist-netting, a male Eastern small-footed bat was successfully captured, examined, and confirmed by biologists from CWF and NJDFW—making it the first verified record of the species at MCR.

The find is especially significant because the nearest known occurrence of the bat was approximately 30 miles away, in southern Morris County. Experts say this extends the known range of the species in New Jersey and suggests that the bat may occupy more areas than previously documented.

The discovery also highlights how human-modified landscapes, such as MCR’s dam and dikes built from excavated rock, may unintentionally support habitat for rare species.

“We’re proud to support this research and thankful to the Conserve Wildlife Foundation and NJDFW’s Endangered and Nongame Species Program,” MCR said. “We look forward to continuing our work together to help protect this unique species and preserve its place in New Jersey’s natural heritage.”