Published: May 2007
Author(s): Steve Germaine and Dave Hays
Northern leopard frogs (Rana pipiens) are now considered sensitive, threatened, or endangered in all western states and provinces. Historically present in Washington in the Columbia, Crab Creek, Pend Oreille, Snake, Spokane, and Walla Walla River drainages, leopard frogs are now only known to occur at Gloyd Seeps and Potholes Reservoir in Grant County. During the summers of 2002 â€" 2005 we intensively surveyed both areas to: a) document extent of leopard frog distributions; b) examine patterns of association among leopard frogs, non-native fish, and bullfrogs; and, c) describe habitat and vertebrate community characteristics associated with leopard frog site occupancy. Surveys covering a 5-km stretch of Crab Creek confirmed only two juvenile leopard frogs at one of three sites occupied during the mid 1990s. At Potholes Reservoir, we surveyed 243 unique sites within 7 management units known to be occupied by leopard frogs during the 1980s. We confirmed leopard frog presence at 87 sites in only 4 management units. Association tests demonstrated that leopard frogs were negatively associated with bullfrogs and non-native predatory fish. We used logistic regression and AIC multi-model comparison techniques to model leopard frog site occupancy at two scales; individual ponds and 1-km2 areas. The most parsimonious model at the pond scale classified 89% of occupied sites correctly. Occupied sites had less tall emergent vegetation, more open water and exposed mud, more herbaceous vegetative cover, and had fewer neighboring ponds containing non-native predatory fish than unoccupied sites. The most parsimonious model at the 1-km2 scale classified 73% of occupied sites correctly. Occupied areas had greater average pond depths, had fewer ponds occupied by bullfrogs and carp, and had greater maximum amounts of herbaceous vegetation. The Gloyd Seeps population now appears defunct, and leopard frogs at Potholes Reservoir appear in sharp decline. Unless immediate and aggressive management of non-native fish, bullfrogs, and wetland vegetation is initiated, leopard frogs may soon be extirpated from both sites, and possibly therefore, from Washington.