Spotted Frog (Rana pretiosa) 



Description: Adults are dark to light brown, gray, or olive green with dark spots (frequently with 

 lighter centers) found on the back, sides and legs. The number and pattern of spotting is quite 

 variable. The back and sides are often covered with small bumps. The underside of the legs 

 is bright red, salmon, or orange. In younger subadults, bright leg color is often lacking and 

 instead a light, lemon-colored wash is present. In subadults there is often a dark mask 

 present, with a light jaw stripe extending to the shoulder. The adult has a snout-vent length 

 of 5-10 cm. Yoimger individuals, without bright legs, may be distinguished by a combination 

 of: 1) dorsal spots not surrounded by light-colored halos; 2) dorsolateral folds present; 3) toes 

 without pads at the tips; 4) light, lemon-colored wash on undersides of legs; and 5) pale gray, 

 not white, belly. Eggs are laid in large, globular masses of 150-500 at the surface of the 

 water. The tadpoles are dark green on top with some gold flecking whereas the underside has 

 an iridescent bronze color. Total length of tadpoles may reach 7 cm; the eyes are located on 

 top of the head. 



Habitat and Habits: Spotted Frogs are regularly found at the water's edge in forest habitats. 

 Forested wetlands up to treeline are used for breeding, but populations are also found in the 

 open inter-mountain valleys with suitable vegetation. Egg masses in a particular pond are 

 often found in the same location at the pond margin. Because of their location, eggs are 

 susceptible to drying up if pond levels recede substantially before tadpoles hatch out. Eggs 

 hatch in 2-3 weeks and tadpoles take 2-14 months to metamorphose, depending on water 

 temperature (Nussbaum et al. 1983, Turner 1958). In 1995 the Spotted Frog was encountered 

 from 3400' in the Bitterroot Valley to over 7000' elevation in the Bitterroot and Sapphire 

 mountains. Tadpoles 1.5-2.5 cm in length were found on 19 May 1995 at the monitoring 

 pond (4350') near the mouth of Lost Horse Canyon; at this same site larger tadpoles were 6 

 cm in length on 16 June, and 7 cm in length (with well-developed hind legs) on 12 July. 

 Single adults (7 cm snout-vent length), but no tadpoles, were seen at Carlton and Little 

 Carlton lakes (7790' and 7740', repectively) on 1 September 1995. Adults (to 8.5 cm snout- 

 vent length), two- and four-legged tadpoles (6 cm in length), and untransformed tadpoles 

 were seen at Dam Creek Lake (7310') on 31 August. Following dispersal, young and adult 

 frogs are usually found not far from open water. 



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

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



Status: The most common frog on the BNF and elsewhere in western Montana; this species was 

 foimd on all Districts in 1995 (Appendix 3), although there are few reports from the East 

 Fork of the Bitterroot River m the Sula District. The Spotted Frog in Montana was a USFWS 

 Candidate (C2C1) species, and is on the Heritage Program "Animal Species of Special 

 Concern" list. Significant declines are evident in western Washington, Oregon, and northern 

 California populations, but recent research (Green et al. 1996) indicates that those 

 populations may be a different species. 



Montana Natural Heritage Program rank: G4 S4. 



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