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How To Help Foothill Yellow-Legged Frogs in Marin
If you enjoy exploring nature in Marin, you'll want to know all about these special frogs that need our help. Scroll down to find out how!
We are making a difference for foothill yellow-legged frogs in Marin, but we need you! Learn how you can help secure a bright future for this special creature found only here in California.
Foothill yellow-legged frogs (Rana boylii) spend much of their lives in or near the streams and rivers that flow through our forests, chaparral, and woodlands. They prefer rocky bottoms and sunny banks over muddier, shadier areas and usually attach their egg clusters to rocks in bright, open spots with flowing water.
The Shrinking Range of Foothill Yellow-legged Frogs in California
These frogs were once widespread throughout California and Marin County. However, decades of land development, dam building, and harmful agricultural practices have drastically decreased their numbers across the state. In Marin County today, they can only be found in a few creeks in isolated, disconnected watersheds.
Click the buttons below to see where the frogs once lived in California and Marin and where they are now.
Historic range of these frogs in Marin was 336,424 Acres
Their current range in Marin is 13, 242 Acres. Please note that frogs have been observed in these watersheds but they don’t represent the precise location of every observation.
Why Are These Frogs So Important?
Foothill yellow-legged frogs are special because they are only found in isolated ranges in California and nowhere else in the world. They also tell us important things about the health of the fast-flowing streams where they live.
As seen in the map above, this species is in significant decline in Marin County, where they are a species of special concern . They are listed as either threatened or endangered everywhere else they live in California besides here and the northwestern part of the state. They are even under consideration for listing under the federal Endangered Species Act.
These frogs need our help!
Public land managers are working hard to protect foothill yellow-legged frogs in our parks and open spaces, giving these isolated populations a chance to survive and even expand. It may be hard to believe, but the main threats to them today are the things we do when we visit the places they live.
How Do We Know?
2020 Foothill Yellow-Legged Frog Egg Mass Counts are Up
- Frog numbers are growing, thanks to the combined efforts of park visitors, scientists, and land managers described above. Specific creeks are monitored throughout the year. The map below shows the total number of unique egg masses found in 2020. Egg masses were observed for the Carson Creek for the first time in 2018.
Click on the circles on the map to see how many egg clusters were found at each site. Map by One Tam / Parks Conservancy. Data source: Garcia and Associates.
We look for the frogs' egg masses in creeks and note several important things like location, what they are attached to (type of creek bottom), water temperature, the depth of egg mass and its size, and more. Females may lay only one clutch of eggs per year, with an average of 1,200 eggs per cluster.
A cluster of frog eggs. Image Credit: Kevin Wiseman
Frogs begin breeding when they are around two to three years old and they can live for over a decade. So, we also monitor adult frogs to get a more complete picture of how the population is doing. We note their GPS locations, sex, and weight, and gently swab their skin for a DNA sample. Each frog also has a unique mottled pattern on their chin, photos of which allow us to recognize and track the same frogs over time.
The same female frog identified by chin mottling in different years. Image Credit: Kevin Wiseman
What Part Do Visitors Play?
People love to explore their parks and open spaces and see animals in their natural habitats, including sometimes wading and playing in creeks. However, foothill yellow-legged frogs like to hide under rocks and lay their eggs in the creek bottom. Tadpoles then metamorphose into frogs in the same season the eggs were laid. Visitors and their pets can unintentionally harm or kill the eggs and tadpoles by trampling on them. Play the video below to learn more.
Video Credit: Marin County Parks
Docents Making a Difference
Volunteer Frog Docents stay by the creek to talk to the public about frogs. They explain how visitors can reduce their impacts to the frogs and their habitat, while still enjoying the experience of seeing them.
These dedicated frog-lovers are helping make a difference!
Dogs in Creek Relative to Docent Shifts
The chart below shows that even though the average number of dogs seen by docents during a shift (solid green line with dashed green trend line) has not changed much over the years, the percentage of those dogs seen in the creeks is on a downward trend (dashed purple trend line).
Learn more about how you can join the docent team each spring.
Click on the different lines on the graph above to learn more about how frog docents are helping protect this species. Dashed line represents overall trend. Graph by One Tam / Parks Conservancy. Data source: Marin County Parks
What We're Doing
We've taken several important steps to improve foothill yellow-legged frog habitat and to protect the frogs that live here. Scroll through the map sequence below to learn more.
Minimizing Human Impacts
Marin Water and Marin County Parks have been working to protect foothill yellow-legged frog habitat at Carson Falls. This map shows the original trail alignments, which ran close to (and even through) the creek, increasing the possibility that a hiker or their pet might unintentionally harm the frogs.
Trail Realignment and Restoration
Multiple trails were re-aligned or decommissioned, and the places where they once passed through were restored.
Rustic Bridge
Closer to Carson Falls, multiple improvements were made, including construction of a new rustic bridge.
Photo Credit: Jacob Seltzer
Viewing Platform & Fencing
New fencing encourages people to enjoy seeing the creek and falls from this natural viewing platform without getting too close to where the frogs' eggs and tadpoles might be sheltering.
Photo Credit: Modern Hiker
Creating Frog-Friendly Creeks
Through years of monitoring a team of scientists noticed egg masses being laid where the Big Carson Creek crosses Pine Mountain Road. The eggs were moved downstream to prevent them from being crushed on the road.
But why would a frog lay its eggs in a road?
The scientists found that, at least in part, it was because this was one of the only sunny spots along the creek. So, in 2013 Marin Water cleared a bit of the canopy downstream to create more places for light to get through. Afterward, although egg masses were still laid in the road crossing, they also began appearing in the newly cleared areas. Any egg clusters that are still being laid in the road are being carefully moved to these safer locations downstream.
The graphics below show how this restoration project played out.
Before
Before the canopy was opened up, egg masses were laid in the road, making them susceptible to being squished.
After
After opening the canopy, while some egg masses were still laid in the road, frogs also began laying in the newly sunny downstream areas.
Success!
Specific creeks are monitored throughout the year. The chart below shows the total number of unique egg masses found across all monitored creeks each year.
Frog egg mass numbers are carefully counted each year. Graph by One Tam / Parks Conservancy. Data source: Garcia and Associates
Number of Egg Masses Counted Each Year are Increasing Compared to the Long-term Average
Yellow bars on the graph below show more egg clusters in recent years, and most importantly that the efforts of visitors and land managers to protect these frogs are paying off.
Yellow bars on the graph above show that the number of foothill yellow-legged frog egg clusters have been increasing in recent years. Graph by One Tam / Parks Conservancy. Data source: Marin County Parks
How You Can Help
Foothill yellow-legged frogs are a rare species where small actions on the part of humans and their furry friends can have a big impact. You can be the hero of this story by staying out of creeks and not collecting tadpoles or frogs.
Saving just one frog or egg mass can actually affect the breeding success of Marin's isolated populations. Eggs and tadpoles are also an extremely important part of the food chain, supporting many other animals such as newts, garter snakes, insects, and birds. Scroll below to see for yourself how much difference protecting egg masses from being squashed can make to the whole environment!
If ALL egg masses are squished...
Female foothill yellow-legged frogs may only breed a few times during their life. To have no egg masses surviving in one year means there will be far fewer frogs to keep the population going.
If ONE egg mass is saved...
On average, there are 1,200 eggs in one cluster! Many of these eggs and tadpoles become food for other creatures like insect larvae and newts. Even saving one egg mass will have a positive effect on the frog population, and nourish many more creatures who live in and around the creek.
If TWO egg masses are saved...
Increasing the number of egg masses that don't get squished also further increases the diversity of the animals that live in and near the creek.
HOORAY! WE SAVED ALL THE EGG MASSES!
By being a frog friend and staying out of the creeks, no eggs were squished! Just look at how we helped all of the wildlife to flourish, including the frogs!
See the links below to find out more about how YOU can help!