Endangered mountain yellow-legged frogs might get a hoppy ending

Sep 18, 2012 by Louis Sahagun

To reach one of the last wild populations of the mountain yellow-legged frog on Earth, Adam Backlin and Elizabeth Gallegos tramped down a no-nonsense trail, scaled cliffs and barged through nettles along a vein of water in a scowling canyon deep in the San Gabriel Mountains.

Finally, the U.S. Geological Survey reached the headwaters of the Mojave River, about 15 miles west of Wrightwood. They forded pools and crawled through underbrush to net as many of the endangered frogs as possible and methodically record their vital statistics.

Recent efforts to save the frogs have included restricting public access and ridding the water of predatory trout. Now, the fist-sized amphibians are breeding in numbers not seen in decades.

When Backlin and Gallegos visited recently, several hundred adult frogs shared the knee-deep pools with hundreds of wiggling and dime-sized babies.

"Whoa!" Backlin shouted, diving head first into a tangle of branches shading a small patch of water boiling with frogs. With one sweep of the net, he pulled out half a dozen. In less than three hours, the biologists captured 71 adults of the species scientists know as Rana muscosa. Fifty-two had been tagged during previous forays into the canyon. But 19 were new frogs.

Two years ago, this 1.5-mile stretch of spring water and ice melt was thought to hold about five.

With skin as permeable as a mop, the species is susceptible to a skin fungus linked to amphibians vanishing around the world. And the fungus and its waterborne zoospores have been detected in mountain yellow-legged frogs.

Batrachochytrium dendrobatidis is a first identified in 1998. It causes a thickening of the skin, which impairs gas exchange and the animal's ability to absorb water, triggering rapid, mass die-offs.

"Exactly how they these frogs are surviving the fungus is a mystery," Backlin said. "One theory is that after the fungus first swept through the San Gabriels in the 1960s - wiping out up to 90 percent of the entire frog population - survivors somehow developed an immunity."

Biologists will study possible defense mechanisms as they search for a cure to the fungus.

The life and times of mountain yellow-legged frogs embody the challenges facing species - and wildlife biologists - in Southern California. For thousands of years, the frogs thrived in almost all of the creeks cascading down the San Bernardino, San Gabriel and San Jacinto mountains.

Since the 1960s, however, the species has been decimated by fires, mudslides, pesticides, fungal infections and loss of habitat, as well as the appetites of garter snakes, raccoons and nonnative fish, bullfrogs and crayfish.

Recent efforts by zoos in Los Angeles, San Diego and Fresno to reintroduce captive-bred frogs into their ancestral haunts have had limited success.

For the time being, the creation of trout-free zones in hard-to-reach streams is one of the most effective survival strategies. For example, in a remote corner of the San Jacinto Mountains, the frogs are starting to recolonize sections of Fuller Mill Creek where fish were removed by the California Department of Fish and Game and the U.S. Forest Service.

Usually found on sunny banks and rocks near riffles, the 3-inch-long frogs are named for the bright yellow extending from the undersides of the hind legs onto the lower abdomen.

"Amphibians in general, and in particular, are resilient - if you give them a chance, they rebound," said Sam Sweet, professor of ecology and evolution at UC Santa Barbara. "One reason they produce huge numbers of eggs is that life is so uncertain for an egg or tadpole. All those eggs compensate for years when creeks dry up, or predators and disease move in and wipe them all out."

Explore further: The influence of the Isthmus of Panama in the evolution of freshwater shrimps in America

2.5 /5 (2 votes)
add to favorites email to friend print save as pdf

Related Stories

Biologists rediscover endangered frog population

Jul 25, 2009

For the first time in nearly 50 years, a population of a nearly extinct frog has been rediscovered in the San Bernardino National Forest's San Jacinto Wilderness. Biologists from the U.S. Geological Survey (USGS) assessing ...

Blood samples show deadly frog fungus at work in the wild

Apr 25, 2012

The fungal infection that has killed a record number of amphibians worldwide leads to deadly dehydration in frogs in the wild, according to a new study by University of California, Berkeley and San Francisco State University ...

Recommended for you

Dogs hear our words and how we say them

18 hours ago

When people hear another person talking to them, they respond not only to what is being said—those consonants and vowels strung together into words and sentences—but also to other features of that speech—the ...

Amazonian shrimps: An underwater world still unknown

19 hours ago

A study reveals how little we know about the Amazonian diversity. Aiming to resolve a scientific debate about the validity of two species of freshwater shrimp described in the first half of the last century, ...

Factors that drive sexual traits

20 hours ago

Many male animals have multiple displays and behaviours to attract females; and often the larger or greater the better.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.