The precarious persistence of the Endangered Sierra Madre yellow-legged frog Rana muscosa in southern California, USA

Abstract

We conducted surveys for the Endangered Sierra Madre yellow-legged frog Rana muscosa throughout southern California to evaluate the current distribution and status of the species. Surveys were conducted during 2000-2009 at 150 unique streams and lakes within the San Gabriel, San Bernardino, San Jacinto, and Palomar mountains of southern California. Only nine small, geographically isolated populations were detected across the four mountain ranges, and all tested positive for the amphibian chytrid fungus Batrachochytrium dendrobatidis. Our data show that when R. muscosa is known to be present it is easily detectable (89%) in a single visit during the frog's active season. We estimate that only 166 adult frogs remained in the wild in 2009. Our research indicates that R. muscosa populations in southern California are threatened by natural and stochastic events and may become extirpated in the near future unless there is some intervention to save them.

Benefits of overwintering in the conservation breeding and translocation of a critically endangered amphibian

“…Our findings are somewhat limited by low individual detection rates in combination with low-density populations but do highlight that detection of brumated frogs was slightly higher than for nonbrumated frogs. Although stream occupancy (presence/ absence) by R. muscosa is highly detectable (Backlin et al 2015), our results confirm that individual visual detection/identification probability is relatively low for this species (10%; (Hammond et al 2020). Moreover, because this species is known to disperse after translocation (Matthews 2003) and mark-recapture models cannot Frogs brumated for 12 weeks showed significantly lighter weights (a) and smaller SULs (b) compared to captive nonbrumated conspecifics until translocation.…”

“…Unlike its closely related counterpart in the north, Rana sierrae, which has been comparatively well studied and is beginning to recover (Knapp et al 2016), much less is known about the ecology and conservation of R. muscosa. Since the 1970's the population has declined from 166 reported locations in Southern California to nine, representing a loss of >99% of its historical range (Hammerson 2008;Backlin et al 2015). The most recent estimates indicate fewer than 200 adult individuals remain in the wild (Backlin et al 2015).…”

“…Since the 1970's the population has declined from 166 reported locations in Southern California to nine, representing a loss of >99% of its historical range (Hammerson 2008;Backlin et al 2015). The most recent estimates indicate fewer than 200 adult individuals remain in the wild (Backlin et al 2015). Decline of the species is attributed to various factors, including chytrid fungus, habitat loss and degradation, and the introduction of nonnative predators (Backlin et al 2015).…”

Reducing the Extinction Risk of Populations Threatened by Infectious Diseases

“…They are currently listed as endangered by the IUCN [59]. There are nine small populations of frogs, persisting in southern California, U.S.A., that require management to avoid extinction [60]. These populations are structured and possess low within-population variation, indicating that the populations are genetically isolated [61].…”

An extirpated lineage of a threatened frog species resurfaces in southern California

“…The California red-legged frog Rana draytonii is the largest native frog (length 4.4–13.8 cm) (Hayes & Miyamoto, 1984; Stebbins & McGinnis, 2012) in the United States west of the Mississippi River and was heavily exploited as a food resource during the Gold Rush era (Jennings & Hayes, 1985). More recently, R. draytonii and other amphibians in southern California have suffered declines as a result of habitat loss, presence of non-native species, and pesticide pollution (Jennings & Hayes, 1994; Fisher & Shaffer, 1996; Davidson et al, 2001; Fellers, 2005; Backlin et al, 2015; Thomson et al, 2016), and are actively managed to stabilize populations and promote conservation. The range of R. draytonii extends from Mendocino County north of the San Francisco Bay and Butte County in the Sierra Nevada, south along the coastal mountains of California into northern Baja California, Mexico (Peralta-Garcia et al, 2016; Thomson et al, 2016).…”