Invasive Bullfrogs Were Destroying Yosemite’s Last Native Turtles – Until Scientists Stepped In
The sound of bullfrogs croaking at night might seem peaceful, but in Yosemite National Park, these invasive amphibians were quietly destroying one of California’s most important native species.
A groundbreaking new study reveals just how devastating American bullfrogs have been for Northwestern pond turtles – California’s only native freshwater turtle species. The results are both alarming and hopeful, showing what happens when nature gets a second chance.
Scientists have discovered something incredible happening in Yosemite’s waterways, writes National Parks Traveler. When researchers removed invasive bullfrogs from certain areas, native turtle populations didn’t just survive – they thrived.
Globally introduced pests
“One reason American bullfrogs are among the top worst globally introduced pests is because they eat everything — anything that fits into their mouth,” explains Brian Todd, a professor at the University of California, Davis, who led the research.
And that includes baby turtles. The problem is so serious that these Northwestern pond turtles could disappear completely from California. “If it disappears, we have no other freshwater turtles that are supposed to be here. It’s part of our natural heritage,” Todd warns.
The research team spent six years tracking turtle populations at four different spots in Yosemite from 2016 to 2022. Half of these locations had bullfrogs, and half didn’t. The difference was shocking – areas without bullfrogs had between two and 100 times more turtles!
Wiped out completely
Even more telling, the only turtles surviving in bullfrog areas were the older, larger ones – too big to fit in a bullfrog’s mouth. The younger generation was being wiped out completely.
But here’s where the story gets exciting. When scientists nearly eliminated bullfrogs from two sites in 2019, baby turtles started appearing again. It wasn’t just turtles that benefited either.
“As bullfrog presence declined, we started to hear other native frogs call and see native salamanders walking around. It’s nice to be able to go back to these sites and hear a chorus of native frogs calling again that previously would not have been heard,” says Sidney Woodruff, the study’s lead author and a doctoral student at UC Davis.
This research, published in Biological Conservation journal, proves that removing invasive species can bring remarkable results. Yosemite’s native wildlife is getting a second chance – and it’s making the most of it.
