The population numbers of the once-endangered Lake Erie watersnake recently got a boost from an influx of the round goby, an invasive fish. Photo by USFWS

COLUMBUS, Ohio, Oct. 14 (UPI) -- Invasive species are like junk foods -- only acceptable as an occasional indulgence, not a substitute for a healthy well-rounded diet.

Researchers at Ohio Study analyzed a range of studies that looked at the effects of invasive species influxes on local predators. Their findings suggest predators benefit from having a bit of extra food sources around -- but only if their traditional dietary sources remain intact.


In other words, invasive species are only beneficial as a treat.

The findings -- which encompassed 109 studies, covering the relationships between 47 species of prey and 93 species of predators -- were detailed in the journal Ecology Letters.

"Eating non-native prey isn't as good for predators as eating native prey," study author Lauren Pintor, an aquatic ecologist at Ohio State, said in a press release. "It may be that the new prey isn't as nutritious, or that the predator hasn't evolved the ability to eat or digest it well."

"But in all these studies, whenever predators' diets were restricted to non-native prey, the predators did not perform as well as they did on native prey," Pintor said. "We only saw a benefit to the predator when the non-native prey provided a supplemental food source."

Researchers say their findings can help conservationists better understand which invasive species pose the greatest threat.

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It's possible some predators will adapt to take better advantage of growing invasive species populations. One of the studies included in the researchers' analysis involved the Lake Erie watersnake, whose endangered status was recently upgraded after it began successfully preying on an influx of round goby.

But the new study suggests such is the exception, not the rule.

"To understand the effects of invasive species on the broader food web, we need a balanced understanding that includes both predator and prey," Pintor said.