An aggregation of overwintering Leopard Frogs, Rana pipiens, and Common Map Turtles, Graptemys geographica, in northern Vermont

An aggregation of at least several dozen Northern Leopard Frogs was observe d in November 1998 at a previously described Common Map Turtle hibernaculum in the Lamoille River, Vermont. The frogs were sometimes under the turtles and were always exposed to well-oxygenated water. We suggest that frogs th at overwinter submerged require a high-PO2 microenvironment, and that this requirement overrides other considerations, such as avoidance of predators.