California Red-Legged Frog

The California Red-legged frog, or Rana draytonii, is a species of frog that is endemic to California and Baja California. It is a medium-sized frog (1.75-5.25 inches) with long legs. Their skin is reddish-brown, gray, or olive with dark spots, and distinctive red hind legs and underbelly, which gives this amphibian it's name. It is classified as vulnerable by the IUCN, with a declining population trend. The California red-legged frog is also California's state amphibian, which gives it extra protection in the eyes of the law.

The habitat of the California red-legged frog includes areas along the coast of California, from Baja California to Mendocino county, as well as in the Sacramento/San Joaquin valley, and the Sierra Nevada Foothills. They tend to inhabit ponds, streams, and other riparian environments, and prefer to live and breed in still, standing water. They are extremely sensitive to the heat of the sun, so they like to hang out in the shade, among tall grasses, shrubs, or reeds, to avoid sunlight.

California red-legged frogs breed in the water, releasing 300-4000 eggs, which hatch into tadpoles in about four weeks. These tadpoles take a long time to turn into young adult frogs--anywhere from four to seven months on average.

The population of the California Red-legged frog has declined due to many factors. The three main threats are overexploitation, habitat degradation/destruction, and invasive species. Overexploitation has occurred in many different forms.

In the late 1800's and early 1900's, the frogs were exploited for food, in the millions, by early settlers to California. Later on, development in the growing state led to degradation of the quality of wetland habitats, wetlands drying up due to irrigation practices, and habitat fragmentation due to housing developments, roads, highways, and farmlands being built on--or next to--these crucial wetland systems. Urbanization has driven the California red-legged frog out of many parts of it's natural habitat. In these areas, species richness goes down, and native species are replaced by non-native, generalist species, such as bullfrogs. Over time, human growth and development has added to the fragmentation of the population. Conservation groups have worked to protect some wetlands that are known native frog habitats from further development.

Agricultural runoff has been shown to be a problem for frogs. Pesticides are environmental pollutants which affect wetlands, streams, and oceans in many ways which have yet to be determined. Some studies have shown that frogs that are exposed to certain pesticides produce more stress hormones and have weakened immune systems. Some frogs have even been "feminized", or turned from males into females. Some scientists think that the negative effects of pesticides seen in frogs indicate that the same chemicals may cause medical problems in humans.

California red-legged frogs have also had to compete with invasive species. Bullfrogs, native to the eastern United States, pose a unique treat to native frogs. They prey on red-legged frogs as a food source, compete with red-legged frogs for the food supply, and also carry an infectious fungal disease called Chritydiomycosis. This disease has decimated native frog populations in many regions. Red-legged frogs are also preyed on by invasive fish species, which are often put in ponds, lakes and streams for recreational fishing. Efforts have been made by conservation groups to improve the habitat of the California red-legged frog by removing invasive species.

The recovery plan for the California red-legged frog, published by the US Fish and Wildlife Service,  has involved splitting it's natural habitat range into "Recovery Units". One of the main objectives of this plan is to reduce threats to the frog, such as environmental pollutants or competing invasive species. Another part of the plan is to restore the frog's habitat zones and protect them from further development or environmental degradation. Scientists hope to restore numbers to the point where a healthy metapopulation, with movements between populations, can be sustained. The ongoing drought has been having a detrimental effect on the frog population, as well. Scientists hope that California will begin to have average rainfall again, and will continue to monitor the numbers for 15 years or more.

If you would like to raise awareness about endangered frog species, please visit SAVE THE FROGS at www.savethefrogs.com. On that website, you can learn all about frogs, the threats to their survival, and what you can do to help! I would also like to recommend the PBS documentary, Frogs: The Thin Green Line. www.pbs.org/wnet/nature/frogs-the-thin-green-line-video-agricultures-effect-on-frogs/4848

Also, I encourage you to research environmental pollutants and their effects on wildlife. Many studies have shown that pesticides, plastics, and other chemicals may cause diseases, birth defects, and other issues in fish, frogs, mammals, and even humans.

Written by Erin Coffey

Sources:

National Wildlife Federation - California Red Legged Frog
https://www.nwf.org/Wildlife/Wildlife-Library/Amphibians-Reptiles-and-Fish/California-Red-Legged-Frog.aspx

U.S. Fish & Wildlife Service - Recovery Plan for the California Red-legged Frog
http://ecos.fws.gov/docs/recovery_plan/020528.pdf

IUCN Red List
http://www.iucnredlist.org/details/136113/0

California Herps - California Red-legged Frog (Images courtesy of this website)
http://www.californiaherps.com/frogs/pages/r.draytonii.html

Save the Frogs - California Red-legged Frog, 2013, Kerry Kriger
http://www.savethefrogs.com/amphibians/rana-draytonii.html

PBS - Frogs: The Thin Green Line, 2009
http://www.pbs.org/wnet/nature/frogs-the-thin-green-line-video-agricultures-effect-on-frogs/4848/

Environmental Working Group - Dirty Dozen Endocrine Disruptors
http://www.ewg.org/research/dirty-dozen-list-endocrine-disruptors