Rare frogs surviving in the Santa Monica Mountains

California red-legged frog. National Park Service.

The first California red-legged frogs to grow up in the Santa Monica Mountains since the early 1970s have made it through their first year. The National Park Service nursed nearly 1,000 eggs into tadpoles and released them last July in two undisclosed stream locations in the mountains. The effort is part of a project to expand the local range of the largest native frogs in the western United States.

From the park service, which says "at least a handful" of the frogs have survived their first year:

“Most studies have found that only one to five percent of frogs in the wild make it to adulthood, so this is not a given,” said Katy Delaney, wildlife ecologist for the National Park Service. “They’re basically teenagers now since it takes them two years to reach adulthood. ”

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The exact number of juvenile frogs is impossible to predict because at this point biologists are relying simply on visual detection during daytime surveys, though they plan to individually mark the animals in the future. Biologists hope that enough frogs will survive to adulthood that they will begin breeding in the spring of 2016.

Another group of more than 1000 tadpoles, transferred as eggs from the source population only a few months ago, were released earlier this week.

The largest native frog in the Western United States, California red-legged frogs are named for the reddish coloring under their legs and belly.

Because frogs have permeable skin that easily absorbs contaminants, they are considered an indicator species that provides important information about habitat health. Nationwide, USGS has documented precipitous declines among amphibians, which some speculate may be linked to habitat loss, invasive species, disease and pollution.