This map layer portrays our current understanding of the distributions of United States and Canadian bat species during the past 100-150 years. Specimen and capture data were obtained from a variety of data sources, including U.S. State natural heritage programs, Canadian conservation data centres, published literature, unpublished reports, museum collections, and personal communications from university, federal, State and local biologists. Records are all specimen, roost, capture, or positive visual identification-based; no acoustic-only identifications were used for this map layer. This map layer reflects minor changes to the July, 2002, data set.