Despite such adaptations and dietary shifts among apex predators, invasive species are still winning. In Australia in 2015, for example, the country’s then-Threatened Species Commissioner told the national broadcaster that “Australia has lost 29 mammals since European colonization, and feral predators are implicated in 28 of these extinctions.”
Florida faces similar invasion problems because it hosts an ideal combination of a subtropical climate, a thriving pet trade and multiple ports of entry. The result, said Ian Bartoszek, a wildlife biologist with the Conservancy of Southwest Florida, is that the state has “more established, nonnative animal species than any country in the world.” Or, as Dr. Mazzotti said about the Everglades, “I’m getting ready to call it the Everglades Invasive Reptile National Park.”
Even in the Everglades, there are pockets of good news. As Burmese pythons eat their way through the Everglades’ medium-sized mammals that consume reptile eggs it is possible, according to Mr. Bartoszek, that loggerhead sea turtles and the vulnerable American crocodile could benefit.
The impact on alligators is less clear. Although there is not yet data to confirm it, “It feels like the alligator is holding the line, and the alligator is most likely responsible for more python predation than we’ve given them credit for,” Mr. Bartoszek said. “The python has found its niche in the marshlands and those areas where there aren’t permanent water bodies where alligators don’t patrol. But in those deeper, more permanent water areas, the alligator has, I believe, locked onto the python, and is definitely doing us a service here.”
These are, so far, relatively small victories in the wider effort to combat invasive species. According to Mr. Bartoszek, 47 bird species, 24 mammal species and two reptile species have been found in the bellies of pythons.
And in the United States, like in Australia, it will take more than crocodiles and alligators to limit such pests. Where apex predators feed on invasive species, much remains uncertain. “Are there clear examples where a single species can and has benefited from an invasive species? You bet,” Dr. Mazzotti said. “What are the other repercussions? We’re a lot less certain about that.”