Northern Leopard Frog {Rana pipiens) 



Description: Adults are brown or green with large, dark spots surrounded by light-colored halos 

 on the sides and back. The dorso-lateral folds are usually lighter in color that the surrounding 

 background. The under-side is typically white, but may be cream-colored or yellowish. The 

 adult has a snout-vent length of 2-5". Newly transformed froglets may lack spots. 



Habitat and Habits: Northern Leopard Frogs are found in or near water in non-forest habitats. 

 Typically the vegetation is dense, e.g., a dense, sedge wet-meadow or cattail marsh. Breeding 

 takes place in lakes, ponds (temporary and permanent), springs, and occasionally backwaters 

 or beaver ponds in streams. Eggs are laid in 2-5" globular masses composed of hundreds to 

 thousands of eggs (Hammerson 1982a, Nussbaum et al. 1983). In Colorado, eggs hatch in 4- 

 15 days and tadpoles take 8-15 weeks to metamorphose, depending on water temperature 

 (Hammerson 1982a). 



Surveying: Both tadpoles and adults are seen in and along the water during the day and can be 

 sampled with a dipnet; adults may also be captured by hand.. 



Status: Historically, the Northern Leopard frog was widespread in Montana but it now appears 

 to have been extirpated throughout much of the western part of the state. Re-surveys of 14 

 known historical sites west of the Continental Divide during the past three summers have 

 failed to reveal a single individual. A population was found at a new site near Eureka, 

 Lincohi County, in 1995 (K. Werner pers. comm.), and two unconfirmed sites are reported 

 from the Missoula area and the Flathead Reservation. No Northern Leopard Frogs were 

 found on or near the BNF in 1995, which included visits to the two historcal sites reported in 

 the 1960's in the Bitterroot Valley. There are a number of large open marsh areas at lower 

 elevations on private land which appear to be good habitat. It is interesting, nevertheless, 

 that there are no historical records from the Missoula area where active collecting occurred 

 during the 1950's-1970's. This suggests that the species may have been localized in 

 distribution in this part of the state and never abundant. It is still common and wide-spread in 

 southeastern Montana, but its status is uncertain in central and northeast Montana. It appears 

 that only localized populations are present on the western edge of the plains. In many other 

 areas in North America where the Northern Leopard Frog was common a few decades ago, it 

 is now gone. Widespread extirpations are known from Alberta (Koonz 1993), Wyoming, 

 Colorado (Hammerson 1982b, Com and Fogelman 1984), Idaho (Groves and Peterson 1992), 

 Washington, and Oregon (Leonard et al. 1993). Bullfrog and fish introductions, acid rain, 

 ozone depletion, immune system suppression, and "Postmetamorphic Death Syndrome" have 

 all been suggested as causes for frog extirpations in other areas (Com and Fogelman 1984, 

 Hammerson 1982b, Carey 1993, Leonard et al. 1993). 



Montana Natural Heritage Program rank: G5 S4. 



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