The Oakland Zoo announced that it has released its 1,000th yellow-legged frog back into the alpine habitats of the Sierra Nevada.
This reintroduction to the Sequoia and Kings Canyon National Park lakes was called "a major milestone" by wildlife recovery program manager Samantha Sammons in a news release, as reported by SFGate.
The yellow-legged frog was once quite abundant in this region of California, but a deadly disease called chytridiomycosis decimated 90% of the population.
Also known as chytrid fungus, the skin-attacking disease has led to "devastating effects" on the species, per the Oakland Zoo. SFGate noted the disease makes it difficult for the amphibians to breathe, take in water, and obtain food. It is also so contagious that it can destroy local populations in a few weeks.
Over the last decade, the Oakland Zoo started raising individuals and releasing them back into the wild to boost population numbers. However, for the batch of tadpoles collected since 2023, the zoo has benefited from an inoculation procedure produced by the University of California, Santa Barbara that acts similarly to a vaccine against the fungus.
In the recovery program, the frogs received anti-fungal chytrid treatments during their froglet stage as well as pit tags, which are the equivalent of microchipping. The U.S. Fish and Wildlife staff track the frogs after they are released into the wild.
Before boarding a helicopter flight into the parks for their final release, the frogs are swabbed with the treatment one last time.
The yellow-legged frogs, although smaller than a golf ball, are an essential part of their ecosystem. This species helps control insect populations, serves as prey to many of the larger animals in the forests, and is so affected by environmental changes that it acts as an identifier for researchers.
The natural balance of these ecosystems can be affected by extreme weather, natural selection, and human behavior. Any time researchers or volunteers step in, like when Oceanographer Anuar Abdullah led ghost nest clearing and coral preservation missions, the work can be incredibly powerful for restoring balance to the ecosystem.
Future plans for this program include developing new methods to breed the yellow-legged frogs, such as genetic rescue or biobanking frog genetics.
Sammons added in the news release, "We need to keep this movement going to continue helping native California wildlife and make sure that these frogs don't disappear."