Pacific Chorus Frog {Pseudacris regilla) 



Description: Adults have a dark conspicuous eye line extending from the nostrils to the shoulder. 

 Basic coloration is quite variable with the background color being green, brown, gray, 

 reddish or bronze. Dark spots and stripes often occur on the head, back, and legs. Most have 

 a dark Y or triangular shaped spot on the head between the eyes. The adult has a snout-vent 

 length of 2-5 cm. Males have a darker throat color and additional folds of skin in the throat 

 region. This is the only frog in Montana with a combination of obvious toe pads and an eye 

 stripe ending at the shoulder. The webbing on the hind feet is very reduced, covering only 

 about 1/2 the length of the toes. Eggs are laid in small clusters of 10-70. The tadpoles are 

 brown/bronze; the eyes are located near the margin of the head when viewed from above, 

 unlike other frog tadpoles in western Montana which have the eyes are on top of the head 

 (except northern chorus frogs, Pseudacris triseriata, which also have the eyes at the margin 

 of the head). 



Habitat and Habits: Pacific 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. Following breeding they 

 move into adjacent uplands and are rarely seen. In western Montana they breed in temporary 

 ponds in lower elevation forests and in intermountain valleys shortly after snow-melt. During 

 the 1995 survey, individuals of this species were observed or heard only at three sites on the 

 Darby District; reproduction was documented at two ponds from May- August, and a calling 

 adult was reported SW of Hamilton on 24 October. At Kramis Pond (4290'), adults were 

 calling and one egg mass was found on 19 May; by 16 June tadpoles were 2.5-6.0 cm total 

 length. At the monitoring pond (4350') near the mouth of Lost Horse Canyon, tadpoles 

 ranged from 1 .5-4.0 cm total length on 16 June, and were 5.0 cm on 12 July. In the Pacific 

 Northwest, eggs hatch in 2-3 weeks and tadpoles take 2-2 1/2 months to metamorphose, 

 depending on water temperature (Nussbaum et al. 1983). Transformed froglets grow quickly 

 following emergence and in Oregon some are sexually mature at 1 year (Nussbaum et al. 

 1983). 



Surveying: Adults may be found during the breeding season in and around ponds and lakes 

 where they breed. Adults are usually heard before they are seen. Adults may call sporadically 

 throughout the summer and fall, especially during wet, warm weather. Tadpoles are seen in 

 the water during the day. 



Status: Little is known about Pacific Chorus Frogs in Montana. The species appears to be 

 widespread but localized in northwestern Montana (Werner and Reichel 1994, Reichel and 

 Flath 1995). Prior to 1995 this species was reported on the BNF only from around Lake 

 Como ( Rodgers and Jellison 1942, Appendix 3), the fu:st known locality for Montana. 

 Whether this population has always been isolated is currently unclear, but the data continue 

 to indicate a very restricted distribution on the BNF. It is encouraging that reproduction is 

 still occuring in the Lake Como area, over 55 years after first discovery there. 



Montana Natural Heritage Program rank: G4 S4?. 



14 



