The Foothill Yellow-legged Frog: Status Update and Steps for Compliance

By Brian Freiermuth, Wildlife Biologist

Foothill Yellow-legged Frog Life History

The foothill yellow-legged frog (FYLF), Rana boylii, is visually one of the more non-descript frogs in California, but it must gamble for survival.  Although FYLF breed in relatively calm parts of streams, these areas are prone to scour from large late-season rains,  or dry out if rains end early.  Tadpoles must metamorphose before fall rains because they can be killed by rushing waters.  To account for this, it is necessary for FYLF to breed early, and this transfers the most risk to eggs.

FYLF egg mass

As a result, large portions of the reproductive effort each year can be lost, even in pristine systems.  Although playing this high stakes game of “river roulette” has allowed the frog to exploit environments that other native species do not, land use conversion and other factors have increased these risks and led to declines in FYLF population.  As a result, FYLF is a candidate for listing under the California Endangered Species Act (CESA).

FYLF Regulatory Status in California

On July 7, 2017 FYLF became a candidate for listing under CESA.  Previously as a Species of Special Concern, measures for FYLF were only reviewed and determined through the California Environmental Quality Act (CEQA) process.  However, species listed under CESA, including candidates for listing, receive additional protections and take without a permit is illegal.

Take is defined under CESA as “to hunt, pursue, catch, capture or kill, or attempt to hunt, pursue, catch, capture or kill.”  If take may occur as a result of a project, an Incidental Take Permit (ITP) from California Department of Fish and Wildlife (CDFW) must be obtained, and as part of the permit approval, take must be minimized and fully mitigated.

Is Listing Likely?

Adult FYLF

WRA experts have been monitoring the review process and we believe that listing of the FYLF as a threatened species under CESA is the most likely outcome.

Advice for Project Proponents

Proponents who operate inside the range of FYLF are advised to consider the species during the constraints analysis phase, project design phase, and CEQA process.  Stream habitats, especially perennial and intermittent ones with coarse surfaces, are the most important for FYLF and as such, projects that propose activities in and around streams will require avoidance of the frog or an ITP if the species is present and take cannot be avoided.   Determining if FYLF is likely to occur at a site is a critical first step in choosing how to proceed.

FYLF breeding habitat

For this reason, a habitat assessment and preliminary survey for FYLF can be extremely informative in determining whether or not avoidance measures or an ITP will be the best path for the project.  Time of year, duration of work, and extent of the proposed work are also important considerations in helping to determine whether measures to avoid FYLF, including an ITP, are necessary.  If your project is within the historic range of FYLF and will result in activities that are in or near stream habitats that could support it, some level of consideration of the frog will likely be necessary for your project.

FYLF Related Services Provided by WRA

WRA provides a range of services to assist our clients in navigating the regulatory environment, including several services that directly consider FYLF.  The table below summarizes some of the services we provide.

Type of Survey or ServiceType of Projects / MeasuresTimeframe / PhaseConsiderations
Habitat assessmentAny project in the range of the species.Constraints analysis / early CEQA process.Included in most wildlife constraints analysis products.
Environmental DNA surveysSurvey technique used to bolster a negative finding of preliminary surveys.Constraints analysis, CEQA process.Relatively new approach to presence / absence. Should be conducted in combination with typical targeted surveys.
Preliminary surveys (presence / absence)Recommended for projects in the range of FYLF with suitable habitat.Best during the spring, when egg masses are present or late summer when tadpoles are metamorphosing. Early CEQA process.CDFW typically requires at least 2-5 surveys.
Egg mass surveysProjects, especially large ones, or those with multiple sites that may support FYLF in all or part of the project area.Breeding season only and scheduled relative to stream conditions / informs ITP application process. Surveys must be done during specific timeframes considering rain and temperature and should be contracted 90 days in advance if possible.Offers an idea of population size and density and identifies most important breeding sites; 2-3 surveys per site recommended. CDFW guidance suggests that breeding sites may require more measures or mitigation.
ITP Application and CDFW consultationNecessary when take of a listed species is likely.Late planning / permitting phase.Best to start early as possible; can take many months to complete.
Pre-construction surveyMeasure for avoidance when FYLF are or may be present.Usually within 3-5 days of commencement of construction activities.Recommended as avoidance measure or required by ITP.
Construction monitoringMeasure for avoidance when FYLF are or may be present.ConstructionRecommended as avoidance measure or required by ITP.


For more information about our services, please contact Rob Schell, Senior Wildlife Biologist.