Experts celebrate surprising return of beloved creature to Yosemite National Park: 'It's part of our natural heritage'

While invasive species can cause an incredible amount of environmental damage, there is still hope for many of the native plants and animals that have been pushed out of their natural habitats, as the recent progress of the northwestern pond turtle demonstrates.

UC Davis reported on the encouraging rebound of native turtle populations in Yosemite National Park in an article shared on Phys.org.

The northwestern pond turtle, together with the related southwestern pond turtle, is a unique part of California's ecosystem.

"All across the state we have one native freshwater turtle, and it's the western pond turtle," said senior study author Brian Todd, per UC Davis. "If it disappears, we have no other freshwater turtles that are supposed to be here. It's part of our natural heritage."

Todd's team published its seven-year study of the turtles in the May issue of the journal Biological Conservation. It examined how the encroachment of the invasive American bullfrog, which is native only to the eastern part of the continent and not California, affected the turtles.

Invasive species are removed from their original habitat and introduced to a new area without competitors or predators that know how to hunt them. Their population balloons, and they either crowd out other species and outcompete them for resources, or — as in the case of the American bullfrog — simply eat them.

The American bullfrog is notorious for eating the young of just about any native species, and its population has gotten out of control.

"At night, you could look out over the pond and see a constellation of eyes blinking back at you," said lead author and Ph.D. candidate Sidney Woodruff, per UC Davis. "Their honking noise is iconic, and it drowns out native species' calls."

But in 2019, steps were taken to get rid of the invasive bullfrog in Yosemite National Park. That's in line with efforts in Oregon to cull the species by encouraging residents to eat it.

Now, northwestern pond turtles are making a comeback. Where once only mature turtles too large to be eaten by bullfrogs survived, now juveniles are appearing again.

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Other species are also benefiting, as is so often the case when balance is restored to one part of an ecosystem.

"As bullfrog presence declined, we started to hear other native frogs call and see native salamanders walking around," Woodruff said, per UC Davis. "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."

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