Anyone who has driven north from Toronto is familiar with the geology of the Canadian Shield. As you reach the southern tip, farms and fields give way to a landscape of rocky granite and colourful gneiss. Less well known, however, are the gems that can be found beneath the surface. While they aren’t crystals or precious minerals, they are equally as valuable - and getting harder to find. Covered in condensation and glittering in from the headlamps, brown bats hang from the ceilings of railways tunnels. The tunnels are a newly discovered hibernacula, offering a warm and safe place for these endangered bats to rest over the winter. In the last 10 years, the arrival of white nose syndrom has decimated the populations of brown bats in Ontario. Some hibernation sites report losses of over 90%! That makes the discovery and protection of new hibernacula critical to restoring the health of this species.