California Red-Legged Frogs

Two adult California red-legged frogs in a shallow stream.
Two California red-legged frogs in a stream during a routine NPS survey.

National Park Service

 
A researcher holding an adult California red legged frog, showing its red hind legs.
Here at Santa Monica Mountains National Recreation Area, we think our frogs are absolutely ribbit-ing! So when the largest native species in the western United States began to decline across its former range and disappeared completely from the Santa Monica Mountains, the National Park Service sprang into action.

A Frog’s Tale

The California red-legged frog (Rana draytonii) was once a common species in Southern California, primarily inhabiting streams and pools that contained water year-round. Unfortunately, Mark Twain’s famous Celebrated Jumping Frog of Calaveras County has all but vanished south of Los Angeles. The population of red-legged frogs in the Santa Monica Mountains and Simi Hills is worryingly small and isolated, and there is great concern about its long-term persistence.
 
A researcher holds an adult California red-legged frog in hand.
An adult California red-legged frog.

National Park Service

What’s the Problem?

The exact reason for the decline of the red-legged frog in Southern California is unknown. Like with many other dwindling species across the world, it’s probably due to a variety of compounding factors.

Los Angeles County is one of the most urbanized areas in the world, home to over 10 million (and counting) people spread across a patchwork of cities and towns connected by massive freeways and developments. Habitat degradation and fragmentation is especially tough for animals like amphibians to cope with – imagine trying to cross a road while being as small as a frog! While natural features like canyons act as barriers to amphibian movement, roads and housing between canyon streams (i.e. Kanan Road, which separates two major creeks) make it even tougher for frogs to disperse. Populations are then split up and isolated from each other, interrupting the natural processes that maintain genetic diversity and stability across them.

Other external factors may include the introduction of the non-native bullfrog, which is larger than the red-legged frog, the red swamp crayfish, and perhaps the deadly chytrid fungus, responsible for wiping out a plethora of amphibian species the world over.
 
A California red-legged frog egg mass underwater.

A Tad of Hope

California red-legged frogs, federally listed as threatened under the Endangered Species Act, appeared to blink out of existence in the Santa Monica Mountains in the mid-20th century. The last confirmed sighting was in the early 1970s, but conservationists were not content to let an iconic species vanish without a fight.

Through a coordinated effort between the National Park Service, the Ventura Office of the U.S. Fish and Wildlife Service, California State Parks, the Mountains Recreation & Conservation Authority, the Santa Monica Mountains Conservancy, the Santa Barbara Zoo, the Santa Monica Bay Restoration Commission, and the U.S. Geological Survey, red-legged frogs were reintroduced to the Santa Monica Mountains in 2014. Egg masses from an adjacent population in the Simi Hills were translocated and placed in pools designated as optimal habitat for the species. Reintroductions to key sites, which were closely monitored, continued in 2015 and 2016.

Then, in 2017, success! During a stream survey on March 14th, NPS researchers found nine egg masses not put there by any human – evidence that the reintroduced red-legged frogs were breeding on their own!
 
A group of biologists kneel in a stream to extract egg masses for relocation.
Biologists with the National Park Service and USGS carefully remove half of an egg mass to translocate to two undisclosed locations in the Santa Monica Mountains.

National Park Service

What’s Next?

The newly established red-legged frog populations in the Santa Monica Mountains will continue to be monitored year-round by NPS ecologist Katy Delaney and her team of dedicated biologists. They are now part of the NPS’s long-term amphibian & reptile monitoring program, which surveys species populations annually.

The species’ recovery will be aided by sustained egg mass reintroductions from the Simi Hills “source” population (which continued in 2017 and 2018), possible new translocation sites, and regular monitoring.

How Can You Help?

We can all take steps to help our amphibian friends and ensure them a better future.

When exploring public lands, take care and tread lightly around aquatic habitats like waterfalls, ponds, and streams. Stay on designated trails and keep your dogs out of the water, as they can disrupt egg masses and eat frogs. Introduction of invasive species like the New Zealand mudsnail, a new but already very serious threat to the park, can occur when an individual enters an uninfected stream after making contact with an infected one. Erosion of soil into bodies of water creates murky, silty environments, which is detrimental to amphibian egg-laying and larval maturation. It can also eventually disrupt hydrological processes, damming certain areas and drying out others further downstream.

Use environmentally-friendly products! Amphibians have extremely thin, permeable skin that’s sensitive to harsh chemicals and irritants. Click here to visit the Environmental Protection Agency’s webpage on using “greener” products and services.

And while this may seem obvious, don’t dump any of your unwanted pets into natural water systems. Exotic species like crayfish, aquarium fish, red-eared sliders, or other pet turtles are the biggest threat to amphibians in the Santa Monica Mountains.
 

More

You can learn about the Service’s herpetofauna monitoring program here.
 

California Red-Legged Frog News Releases

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    Tags: Frog News

    Last updated: November 1, 2018

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