California Red-Legged Frogs

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

National Park Service

 

Here at Santa Monica Mountains National Recreation Area, we think our frogs are absolutely ribbit-ing! So when the largest native frog 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, especially since the Woolsey Fire swept through the area in November 2018.

 

An adult California red-legged frog.

National Park Service

What’s the Problem?

The exact reason for the decline of the California 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 frogs live in canyon streams, roads and housing between canyons (i.e. Kanan Road, which separates two major creeks) make it tough for frogs to disperse. Populations are 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 California 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.

 

The Happy Seasons Pre-Woolsey Fire

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, California State Coastal Conservancy, and the U.S. Geological Survey, California red-legged frogs were first reintroduced to the Santa Monica Mountains in 2014. Egg masses from an adjacent population were translocated and placed in pools designated as optimal habitat for the species. Reintroductions to key sites, which were closely monitored, continued annually .

Then, in 2017, success! During a stream survey in March, NPS researchers found nine egg masses not put there by any human – evidence that the reintroduced California red-legged frogs were breeding on their own!

 

The Woolsey Fire - A Major Setback for the Rare Species

In the fall of 2018, these rare amphibians were flourishing, happily eating insects, and reproducing on their own in two of the four streams spread throughout the mountains. Then the Woolsey Fire struck in November 2018 and burned up much of their habitat. This was immediately followed by a season of heavy rainfall, which caused debris flows that filled the streams with silt and mud.

A year later, biologists discovered adult frogs at all of the sites that had survived the fire and silt.

Currently, there are a couple of reintroduction sites in and around the Santa Monica Mountains where the frogs are thriving and back to their pre-fire breeding numbers. That's the heartening news. In others, however, the habitat was severely damaged and it's unclear how the frogs will fare in the long run. The sites remain heavily silted from mudslides that occurred when it rained post-fire and there is little suitable breeding habitat for the frogs.

In recent months, the frogs at some sites have been difficult to find due to the thick vegetation and the fact that there are limited "good" pools for the frogs to hang out in.

 

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?

What’s next is a good question that no one can answer yet.

What we do know is that regardless of the many challenges they’ve encountered over the last several years, these frogs are much more resilient than we ever expected!

As part of the NPS’ long-term amphibian and reptile monitoring program, which surveys species population annually, our dedicated team, made up of NPS ecologist Katy Delaney and biological technician Sarah Wenner, will continue to monitor the hardy population.

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.