Western Chorus Frog {Pseudacris triseriata) 



Description: Adults are very small (0.75-1.5") and have tiny, almost unnoticeable toe pads. They 

 have a dark line extending from the snout through the eye to the groin. Basic coloration is 

 quite variable with the background color being green, brown, gray, or reddish. Typically 3-5 

 dark longitudinal stripes are present on the head and back which may be broken up into spots 

 on some individuals. 



Eggs and Tadpoles: Eggs are laid in small clusters of 10-100, usually less than 1 " across and 

 attached to submerged vegetation (Wheeler and Wheeler 1966, Baxter and Stone 1985). 

 Individual eggs are about 1 mm in diameter. Tadpoles are brown/bronze and the eyes are 

 located on the sides of the head. 



Similar species: Has tiny toe pads. Recently metamorphosed Ranid frogs could be confused with 

 this species, but the coloration differs and the tiny toe pads are lacking. Eye position 

 distinguishes the tadpoles. 



Habitat and Habits: Western Chorus Frogs are regularly found in the water only during the 



breeding period in spring. Their presence is obvious during this time due to their call, which is 

 given frequently at night and sporadically throughout the day. Calls were frequently heard 

 until late June. Eggs or tadpoles were found in ponds from 24 April to 22 July in 1998. 

 However, the species was detected (tadpoles) on only 1 of 14 July site surveys. For standard 

 site surveys (i.e., excluding nocturnal roadside call surveys) in 1998 where the species was 

 present (n = 61), tadpoles were detected in 1 of 20 April surveys, 12 of 19 May surveys, and 

 17 of 22 June surveys (G = 28.016, df = 2, P < 0.001), indicating a peak of breeding in May 

 and June. Following breeding, these frogs move into adjacent uplands and are rarely seen. In 

 eastern Montana, they breed in temporary ponds and small lakes surrounded by prairie, in 

 some locations in Montana they are also found in open forested habitats. Eggs hatch in about 

 2 weeks and tadpoles are about 2 months old at metamorphosis (Wheeler and Wheeler 1966, 

 Nussbaum et al. 1983). 



Surveying: Adults are easy to survey, using their calls for identification during the breeding season 

 in spring and early summer. During the breeding season, adults may also be seen in the water, 

 but their small size and habit of freezing or diving when disturbed makes observation difficult, 

 night surveys may be more productive. Egg masses are difficuh to find. Tadpoles may be 

 seen in ponds during the day and can be sampled with a dipnet. 



Status: Common across the prairies of eastern Montana, including throughout the Miles City 

 District, BLM, and the most frequently encountered amphibian in eastern Montana. This 

 species was found on 69 surveys in 12 counties in 1998 (Appendix 2), and in Carbon County 

 on 1 survey (and 5 opportunistic encounters) in 1995 (Appendix 3b and 4). 



Montana Natural Heritage Program rank: G5 S5. 



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