Foothill yellow-legged frog conservation assessment in California

Hayes, Marc P.; Wheeler, Clara A.; Lind, Amy J.; Green, Gregory A.; Macfarlane, Diane C.

doi:10.2737/psw-gtr-248

Cited by 11 publications

(8 citation statements)

References 99 publications

(154 reference statements)

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“…Foothill yellow-legged frogs primarily depend on a narrow range of in-river conditions to support all life-stages. Rivers where they occur are typically described as containing rocky, unconsolidated substrates with broad and slow-moving water, and unshaded allowing ample sunlight (2). Unconsolidated rocky substrates in slow-moving water provide stable locations for egg-laying, and seasonally warming water temperatures with ample sunlight support formation of algae, the food source of tadpoles (7,10).…”

Section: Study Organism and Study Areamentioning

confidence: 99%

“…Lotic-dependent amphibians are frequently of conservation concern as they often have narrowly defined ecological tolerances and are sensitive to human-caused disruptions to hydrological processes, including alterations to substrate and flow, temperature, as well as disease, invasive species, and other factors (1,2). Identifying the range of conditions in which these amphibians can occur but also anthropogenic disturbances to rivers or competitive interactions that may have constrained their current distribution can inform species management and conservation, particularly at range margins (3).…”

Section: Introductionmentioning

confidence: 99%

“…Foothill yellow-legged frogs (Rana boylii) in western Oregon are at their northern range edge, have experienced an approximately 41% distributional contraction, and are currently being considered for protection under the United States endangered species act (4). Across their range, they are a species of conservation concern, and water development and diversions, including for agriculture, that cause inconsistent flow regimes, change average or variation in river temperature, water chemistry, and alter river-bed geomorphology, or provide conditions favorable to invasive species are thought to be the primary cause of observed declines (1,2,5,6).…”

Section: Introductionmentioning

confidence: 99%

“…Foothill yellow-legged frogs inhabit and breed in slow-moving rivers that contain coarse substrates (e.g. gravel bars, larger cobbles, and bedrock >2 mm; (7)) with limited streamside vegetation in western Oregon and California (2). Breeding coincides narrowly with summer drought and warming river temperatures, and foothill yellow-legged frogs may be particularly sensitive to alterations to water temperature, and high flow volumes that wipe away egg-masses during breeding season (2,(8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

“…Cessation of annual burning by native peoples to clear vegetation increased recruitment of streamside vegetation, potentially shading rivers and reducing suitability for foothill yellow-legged frogs (12). Dams, although not as widespread in western Oregon as in other parts of their range, have been linked with direct negative impacts by altering river temperatures, flow volume, and timing, and indirect effects if those alterations facilitate invasion by non-native species (1,2). These disturbances are likely to negatively affect local, breeding populations of foothill yellow-legged frogs and potentially disrupt connectivity among populations via barriers and by increasing distances between populations (2).…”

Section: Introductionmentioning

confidence: 99%

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Historical disturbances to rivers appear to constrain contemporary distribution of a river-dependent frog

Linnell

Davis

2021

Preprint

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Frogs dependent on lotic environments are sensitive to disturbances that alter the hydrology (e.g., water impoundments), substrate (e.g., debris torrents), and riparian vegetation (e.g., wildfires) of river ecosystems. Although rivers are often very dynamic, disturbances can push environmental baselines outside of narrowly defined ecological tolerances under which a species evolved. Short-lived lotic-dependent organisms, restricted to movements within the water or the riparian corridor, are at risk of local extirpations owing to such disturbances if they fragment and isolate affected populations from recolonizing source populations. In Oregon, USA, the foothill yellow-legged frog (Rana boylii) is at its northernmost range margin and has experienced an approximately 41% range contraction compared to their historical distribution. To inform conservation and management, we used species distribution models to identify environmentally suitable watersheds based on intrinsic baseline environmental variables, and then examined potential effects of human-caused alterations to rivers, including splash dams used to ferry timber downstream prior to 1957, large water impoundments, and adjacency to agricultural croplands. We used machine-learning in program Maxent and three different river layers that varied in extent and location of mapped rivers but contained distinct information to produce species distribution models which we then combined into a single ensemble model. Stream order, annual precipitation, and precipitation frequency were the highest ranked baseline environmental variables in most models. Watersheds with highly suitable baseline conditions in our ensemble model were negatively correlated with anthropogenic disturbances to rivers. Foothill yellow-legged frogs appeared to be sensitive to human-caused disturbances to rivers, perhaps indicative of their narrow ecological tolerance to in-river conditions. We do not anticipate variables in our model to change much through time. Rather, for conservation we identified potential legacy (spash dams) and ongoing human-caused disturbances that are more likely to change conditions for the species in the short- and long-term.

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Section: Study Organism and Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Historical disturbances to rivers appear to constrain contemporary distribution of a river-dependent frog

Linnell

Davis

2021

Preprint

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Rapid extirpation of a North American frog coincides with an increase in fungal pathogen prevalence: Historical analysis and implications for reintroduction

Adams

Pessier

Briggs

2017

Ecology and Evolution

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As extinctions continue across the globe, conservation biologists are turning to species reintroduction programs as one optimistic tool for addressing the biodiversity crisis. For repatriation to become a viable strategy, fundamental prerequisites include determining the causes of declines and assessing whether the causes persist in the environment. Invasive species—especially pathogens—are an increasingly significant factor contributing to biodiversity loss. We hypothesized that Batrachochytrium dendrobatidis (Bd), the causative agent of the deadly amphibian disease chytridiomycosis, was important in the rapid (<10 years) localized extirpation of a North American frog (Rana boylii) and that Bd remains widespread among extant amphibians in the region of extirpation. We used an interdisciplinary approach, combining interviews with herpetological experts, analysis of archived field notes and museum specimen collections, and field sampling of the extant amphibian assemblage to examine (1) historical relative abundance of R. boylii; (2) potential causes of R. boylii declines; and (3) historical and contemporary prevalence of Bd. We found that R. boylii were relatively abundant prior to their rapid extirpation, and an increase in Bd prevalence coincided with R. boylii declines during a time of rapid change in the region, wherein backcountry recreation, urban development, and the amphibian pet trade were all on the rise. In addition, extreme flooding during the winter of 1969 coincided with localized extirpations in R. boylii populations observed by interview respondents. We conclude that Bd likely played an important role in the rapid extirpation of R. boylii from southern California and that multiple natural and anthropogenic factors may have worked in concert to make this possible in a relatively short period of time. This study emphasizes the importance of recognizing historical ecological contexts in making future management and reintroduction decisions.

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Estimating the survival of unobservable life stages for a declining frog with a complex life history

et al. 2021

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Demographic models enhance understanding of drivers of population growth and inform conservation efforts to prevent population declines and extinction. For species with complex life histories, however, parameterizing demographic models is challenging because some life stages can be difficult to study directly. Integrated population models (IPMs) empower researchers to estimate vital rates for organisms that have cryptic or widely dispersing early life stages by integrating multiple demographic data sources. For a stream‐inhabiting frog (Rana boylii) that is declining through much of its range in Oregon and California, USA, we collected egg‐mass counts and capture–mark–recapture data on adults from two populations in California to fit IPMs that estimate adult abundance and the survival rate of both marked and unobserved life stages. Estimates of adult abundance based on long‐term monitoring of egg‐mass counts showed that study populations fluctuated greatly inter‐annually but were stable at longer timescales (i.e., decades). Adult female survival during 5–6 yr of capture–mark–recapture study periods was nearly equal in each population. Survival rate of R. boylii eggs to the subadult stage is low on average (0.002) but highly variable among years depending on post‐oviposition stream flow. Population viability analysis showed that survival of adult and subadult life stages has the greatest proportional effect on population growth; the survival of egg and tadpole life stages, however, is more malleable by management interventions. For example, simulations showed head‐starting of tadpoles, salvaging stranded egg masses, and limiting aseasonal pulsed flows could dramatically reduce the threat of extirpation. This study demonstrates the value of integrating multiple demographic data sources to construct models of population dynamics in species with complex life histories.

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Foothill yellow-legged frog conservation assessment in California

Cited by 11 publications

References 99 publications

Historical disturbances to rivers appear to constrain contemporary distribution of a river-dependent frog

Historical disturbances to rivers appear to constrain contemporary distribution of a river-dependent frog

Rapid extirpation of a North American frog coincides with an increase in fungal pathogen prevalence: Historical analysis and implications for reintroduction

Estimating the survival of unobservable life stages for a declining frog with a complex life history

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