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 observed 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 that overwinter submerged require a high-PO sub(2) microenvironment, and that this requirement overrides other considerations, such as avoidance of predators.