132 



Reptitci mill Ainpliihuins — 0:ir Lniiit; Rfsoiirces 



Status 



All species studied have suffered declines in 

 distribution and abundance, largely because of 

 habitat loss or modification from farming, graz- 

 ing, logging, urban development, suppression 

 of bru.sh fires, and flood-control or water-devel- 

 opment projects. The species have also been 

 affected by the widespread introduction of ver- 

 tebrate and invertebrate aquatic predators. 



Northern Red-legged Frog {Rana aurora 

 aurora) 



This frog, restricted to lower elevations (300 

 m |984 ft]) of the north coast region of 

 California (Fig. 1 ), has disappeared from about 

 15% of its historical range in California. It is 

 not in danger of extinction in the state. 



Fig. 1. Historical and current distribution of the northern red-legged frog. California red-legged 

 frog, and Cascades frog in California based on 2,068 museum records and 302 records from other 

 sources. Dots indicate locality records based on verified museum specimens. Squares indicate 

 locality records based on venfied sightings (e.g.. field notes, photographs, pubhshed papers). Red 

 dots and green squares denote localities where native frogs are extant. Gold dots and blue squares 

 indicate where native frogs are presumed extinct. Figure modified from Jennings and Hayes 

 (1993). 



California Red-legged Frog (/?.«. draytonii) 



This frog was originally found over most of 

 California below 1,524 m (500 ft) and west of 

 the deserts and the Sierra Nevada crest (Fig. 1 ). 

 Although the California red-legged frog has 

 now disappeared from about 75% of its histori- 

 cal range in the state, around the turn of the cen- 

 tury it was abundant enough to support an 

 important commercial fishery in the San 

 Francisco fish markets (Jennings and Hayes 

 1984). California red-legged frogs have almost 

 completely disappeared from the Central Valley 

 and southern California since 1970 and are cur- 

 rently proposed for listing as endangered by the 

 U.S. Fish and Wildlife Service (Federal 

 Register 1994). 



Cascades Frog {R. cascadae) 



The Cascades frog was originally found in 

 northern California above 230 m (755 ft: Fig. 

 I ). where it was historically very abundant. 

 Since the mid-1970's, the species extensively 

 declined, disappearing from about 50% of its 

 range in the state. No habitat loss hypothesis 

 adequately explains why this frog survived with 

 cuiTcnt land-use practices for over 50 years 

 before its decline. It is still abundant in 

 California only in the northern third of its range 

 on lands under federal ownership. 



Foothill Yellow-legged Frog [R. boylii) 



This frog was originally found over most of 

 California below 1 .829 m (6,000 ft), west of the 

 deserts and the Sierra-Cascade crest (Fig. 2). In 

 many locations before 1970, populations con- 

 tained hundreds of individuals (Zweifel 1955), 

 but the frog has now completely disappeared 

 from southern California and from about 45% 

 of its historical range over the entire state. Most 

 populations were apparently healthy until the 

 mid-1970"s. when a population crash occurred 

 in southern California and the Sierra Nevada 

 foothills after several years of severe floods and 

 drought, which may have been responsible for 

 the declines, although it is not certain. Because 

 this species was an important component of the 

 food web in many streamside ecosystems, its 

 loss has probably negatively affected several 

 organisms, such as garter snakes (Thamnophis 

 spp.), which historically relied upon it as a 

 major food source. 



Spotted Frog (R. pretiosa) 



The spotted frog was historically recorded 

 only from scattered localities in the extreme 

 northeastern part of California below 1,372 m 

 (4.500 ft), where it was apparently restricted to 

 large marshy areas filled by warmwater (more 

 than 20°C [68°F]) springs (Fig. 2). It has now 



