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-latcral folds (ridges along the sides of the back) 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 body length of 2-5". Newly transformed 

 froglets may lack spots and are about 1" in length (Leonard et al. 1993). 

 Eggs and Tadpoles: Eggs are laid in 2-5" globular masses composed of hundreds to 

 thousands of eggs (Hammerson 1982a, Nussbaum et al. 1983). The tadpoles are brown to 

 dark browTi on top with some metallic flecking, whereas the underside is often nearly 

 transparent (Nussbaum et al 1983). Total length of tadpoles may reach more than 3"; the 

 eyes are located on top of the head. 



Similar species: None, although some newly-transformed froglets may lack spots, which makes 

 them extremely difficult to distinguish from Spotted and Wood Frogs. 



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

 Vegetation is typically dense, as in a cattail marsh or dense sedge-meadow. Breeding takes 

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

 beaver ponds in streams. In Colorado, eggs hatch in 4-15 days and tadpoles take 8-15 weeks 

 to metamorphose, depending on water temperature (Hammerson 1982a). 



Surveying: Both adults, tadpoles, and eggs are easily seen in and along the water during the day 

 and can be sampled with a dipnet; adults may also be captured by hand. At very low 

 densities adults may be difficult to find and may be detected using a call recorder. Tadpoles 

 are difficult to tell from those of the Spotted Frog in areas where the two species may 

 overlap. 



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

 to be extinct tliroughout much of the western part of the state. It is still common and 

 widespread in the southeastern comer of the state, but it may be declining in central and 

 northeastern Montana. It appears that only localized populations are present on the western 

 edge of the plains. A single report of this frog is known from the HNF; an obsers'ation of one 

 was made near McDonald Pass in 1994. Given the recent declines in this species and the 

 unusual habitat, this record should be treated as hypothetical until verified. Several other 

 records exist from near HNF lands at lower elevations. The most recent record was of a few 

 individuals seen at the Deepdale Fishing Access south of Townsend in 1994; however, 

 despite three surveys, none were seen in 1995. Due to its significant decline and lack of 

 current reports from the HNF, all sightings of this species should be documented. 



Northern Leopard Frogs are now absent from many other areas in North America where 

 they were common a few decades ago. Widespread extinctions are known from Alberta 

 (Koonz 1993), Wyoming (Koch and Peterson 1995), Colorado (Hammerson 1982b, Corn 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 e/o/. 1993). 



Montana Natural Heritage Program ranJ<:: G4 S3S4. 



26 



