Photo: Michael Grace

A mass die-off of tens of thousands of bats in the U.S. Northeast is confounding researchers and worrying wildlife advocates. The phenomenon has been dubbed white nose syndrome since many of the dead and dying bats show a white fungus on their nose. However, the fungus itself is believed to be a secondary symptom; the primary cause is as yet unknown. Officials estimate that white nose syndrome has had a 50 to 90 percent mortality rate in those afflicted. “We’ve never seen anything like this before with our bats, much less any other mammals, with a very large regional die-off,” said Susi von Oettingen of the U.S. Fish and Wildlife Service. Bat advocates aren’t the only ones worried about the plummeting population. Farmers and others will likely miss the bats later this year since the disappearance of whole populations could mean a much larger number of insects. So far, the disease has been found in Connecticut, New Hampshire, New York, Massachusetts, Rhode Island, and Vermont, though biologists say it could easily spread to other regions.