Ryan's previous research has shown that the hybrid larvae even deploy an ambush strategy: When something swims by, the creatures attack and "jump and suck at the same time," she explained.
All aquatic salamanders are suction feeders, but the hybrids are more effective because of their large size, she added.
The hybrids have another strange adaptation, she added: Tadpoles will sometimes develop extra rows of teeth and become cannibals, something not seen in the native species.
Also at Risk
Other amphibian species are in danger if the hybrid's range continues to spread throughout the valley.
For instance, the Santa Cruz long-toed salamander, also listed as endangered in the U.S., lives in a very small range in Monterey County.
If hybrids moved into this area, they "could put a serious dent into the whole global population of the [long-toed] salamander," Ryan said.
Karen Lips, an amphibian biologist at the University of Maryland, College Park, said in an email that "the results of the paper show that the hybrids are having a significant impact on the other amphibians in these ponds."
And there are other examples in which salamanders have become top predators, added Lips, who was not involved in the research. In woodland ponds, for example, the amphibians dictate the populations of insects and other invertebrates.
Getting rid of the hybrid poses "ethical quandaries," study leader Ryan said.
"From a conservation perspective, there [are] a lot of deep questions about what to do with this," she said.
After all, the hybrid is part endangered species, so "do we protect [them] because they're part native?"
Overall, Ryan said, her "real concern" is for the survival of California's native salamander, which has shown to be no match for the half-Texan interloper.
The hybrid's more aggressive predation "benefits the hybrid and harms the native, speeding up the process of converting populations into more hybrids."
Research appears this week in the journal Proceedings of the National Academy of Sciences.
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