SAN FRANCISCO— The California Fish and Game Commission, in response to a Center for Biological Diversity petition, voted today to designate all populations of the mountain yellow-legged frog as a candidate species, the first step toward a formal listing as endangered or threatened under the state’s Endangered Species Act. The frogs live in high-elevation waters in California’s Sierra Nevada and Transverse ranges.
“A state endangered listing is critical for preserving mountain yellow-legged frogs, especially since the federal government has inexplicably refused to extend Endangered Species Act protection to the species in the Sierra Nevada,” said Jeff Miller at the Center. “These frogs were once incredibly abundant and a key component of the high Sierra ecosystem, but for decades have been on an alarming slide toward extinction.”
Unfortunately, the Commission also adopted emergency rules today allowing exemptions from “incidental take” prohibitions — killing or capture of frogs — during activities such as the state’s environmentally damaging fish-stocking program, operations of dam, reservoirs and water diversions, and for timber harvest plans. The Center has twice sued the Department of Fish and Game to force evaluation of the full environmental impacts of the fish-stocking program, and is seeking adequate measures to prevent stocking from harming frogs and other imperiled aquatic species.
“The Commission took an important step forward today but then took a half-step back by adopting take exemptions. These frogs are on a rapid trend to extinction and will need greater protection to survive and recover in the wild,” said Lisa Belenky, a Center attorney.
Just a few decades ago, these hardy survivors of freezing winters were abundant around many alpine lakes. But yellow-legged frog populations are collapsing due to predation by introduced trout, spread of diseases that may be exacerbated by pesticides, and habitat changes caused by development, climate change, drought and livestock grazing. Surveys since 1995 have revealed that 93 percent of northern and central Sierra populations and 95 percent of southern populations have already been lost.
The Commission’s acceptance of the listing petition initiates a formal status review of both the Southern California and Sierra Nevada species of mountain-yellow-legged frog, with a final determination on listing to be made by the Commission after one year. Candidate species receive the same protected status as state endangered and threatened species during the candidacy period.
Mountain yellow-legged frogs are adapted to high-elevation habitats without aquatic predators. Widespread stocking of nonnative trout in high-elevation Sierra lakes by the California Department of Fish and Game has been a primary cause of decline of the species. Introduced trout prey on tadpoles and juvenile frogs and change the food web of the aquatic ecosystems on which frogs depend. Since 2000, the National Park Service and U.S. Forest Service have begun removing nonnative trout from some high Sierra lakes on federal lands in an attempt to restore yellow-legged frog populations.
In 2006 the Center for Biological Diversity filed suit against Fish and Game for failing to complete an environmental review of the impacts of fish stocking on sensitive aquatic species; in 2007 a court ordered the state agency to conduct a public review of the stocking program’s impacts. In 2008 Fish and Game agreed to interim restrictions prohibiting stocking trout in water bodies with species sensitive to nonnative fish. In 2010 Fish and Game released a flawed environmental impact report regarding the fish stocking program, leading to another Center lawsuit in February. Although the state has taken some steps to reduce trout stocking in areas with yellow-legged frogs, stocked trout continue to harm frog populations and limit recovery. Permanent protection and management decisions to stop stocking and remove trout in key frog habitats are necessary to reduce trout predation of mountain yellow-legged frogs.
Only part of the population of Southern California mountain yellow-legged frogs is currently protected as endangered under the federal Endangered Species Act. In 2000, the Center for Biological Diversity petitioned for federal endangered status for mountain yellow-legged frogs throughout the Sierra Nevada. Although the U.S. Fish and Wildlife Service determined that Sierra populations also warrant endangered status, the agency refused to confer federal protection, instead placing them on the candidate list.
Recent research has linked pesticides that drift from agricultural areas in the Central Valley to declines of native amphibians in the Sierra Nevada. Pesticides and other pollutants can directly kill frogs and also act as environmental stressors that render amphibians more susceptible to diseases, including a chytrid fungus that has recently ravaged many yellow-legged frog populations.
Mismanagement of national forest lands has degraded frog habitat where livestock grazing, logging, off-road vehicles and recreational activity are allowed in frog habitat. Rapid climate change has brought warmer temperatures, decreases in runoff, shifts in winter precipitation in the Sierra from snow to rain, and habitat changes that are rendering frog populations more vulnerable to drought-related extinction events.
The mountain yellow-legged frog was recently re-described by scientists as two distinct species: the southern mountain-yellow-legged frog (Rana muscosa), which occurs in the southern Sierra and Transverse ranges of Southern California; and the Sierra Nevada mountain yellow-legged frog (Rana sierrae), inhabiting the central and northern Sierra.