Endangered California frogs are receiving an immunity boost from scientists who are capturing them from remote Sierra Nevada ponds and transporting them to city zoos for inoculation, officials announced on Wednesday. The experiment aims to rescue the 3-inch mountain yellow-legged frog, named for the distinctive colouring under its hind legs.
Scientists use nets to capture diseased tadpoles, then fly them by helicopter from their natural range within Sequoia and Kings Canyon National Parks. They are then driven over 200 miles across the state to the San Francisco and Oakland zoos, where they are vaccinated against a ravaging disease partly blamed for wiping them out from much of their historical range in the Sierra.
Roughly 385 frogs have been treated at the zoos and returned after two years as healthy young adults to their native lakes and ponds. Aquatic ecologist Danny Boiano of the Sequoia and Kings Canyon National Parks, who has led the three-year project, said it appears to be paying off. Next, his team will study the frogs to determine if the treatment is working.
The species once thrived in such numbers that people could not walk the shores of lakes and ponds without stepping on them. Their decline began a century ago with the introduction of non-native trout for sport fishing that ate the tadpoles. Starting in the 1960s, the frog suffered a second blow from an invasive disease called chytrid fungus, blamed for the decline and extinction of more than 200 amphibian species worldwide. Today, the mountain yellow-legged frog is missing from 90 percent of its historical range in the Sierra.
Inoculating the frogs in Sequoia and Kings Canyon National Parks costs roughly $175,000 a year, mostly to pay the team of 10 seasonal biologists. 'Just like vaccinating people, we are jump-starting their disease-fighting immune systems,' said Jessie Bushell, director of conservation at the San Francisco Zoo. 'Letting the population completely die out is not a good option.'
