Hidden away in the woods near the upstate New York town of Lake George is a cave. The entrance of the cavern, an abandoned graphite mine, is almost perfectly round, with a trickle of water running out of it. On a weekday morning in late February, researchers, led by Carl Herzog, a wildlife biologist for the New York State Department of Environmental Conservation, gather at the cave mouth and swap hiking boots for waders before filing in.

Kate Ritzko, a fish and wildlife technician for th