Observations of Atypical Habitat Use by Foothill Yellow-Legged Frogs (Rana boylii) in the Coast Range of California

Abstract

Foothill Yellow-legged Frogs (Rana boylii) have experienced extreme range-wide declines in recent decades. This stream-dwelling species is thought to be in decline primarily due to the alteration of streams through anthropogenic water development, the effects of which may be exacerbated by climate change. Although R. boylii has long been considered an obligate inhabitant of perennial streams, recent observations indicate that this species exhibits greater behavioral plasticity in habitat use, particularly for reproduction. Herein, we report on several observations of R. boylii using atypical habitat for both refuge and reproduction. We found several R. boylii individuals reproducing within lentic habitat over a several year period. We also found up to 27 egg masses of R. boylii in a primarily mud-substrate intermittent stream, where the species bred and recruited individuals in 5 of 10 years. Behavioral plasticity in the use of habitat types described herein indicates a possible search bias in traditional Rana boylii surveys. Our observations may have implications for future assessment of R. boylii habitats and for species recovery.