If you thought that the praying mantis was an innocuous, almost zen-like insect with a passive demeanor then prepare to have your world turned upside down. Researchers have found that these aggressive carnivorous insects, known to eat small frogs and lizards, also kill and eat small birds. A study by an international group of zoologists has, for the first time, documented this frightening behavior and revealed it is happening all over the world.

Anecdotally, many may already be aware that praying mantises can kill and eat birds. A quick YouTube search yields a torrent of horror-show videos showing the behavior, with hummingbirds captured at domestic feeders often on the receiving end.

A new study by a team of zoologists has systemically documented 147 examples of mantises eating birds, showing that 12 species and nine genera are known to attack small birds. The team tracked the behavior across 13 countries, finding mantises preyed on 24 different species of birds.

"The fact that eating of birds is so widespread in praying mantises, both taxonomically as well as geographically speaking, is a spectacular discovery," says lead author of the study Martin Nyffeler from the University of Basel.

Interestingly, over 70 percent of the documented cases were found in the United States, with hummingbirds making up the majority of victims. The ubiquity of the behavior in the US could be traced back to the release of several alien mantis species in the late 1800s.

Praying mantises have been utilized in gardens for decades as biological pest control agents, and to this day many still use both imported and native species for pest control purposes. But the new research shows the insects do pose a threat to hummingbirds and small passerine birds.

"Our study shows the threat mantises pose to some bird populations," says Nyffeler, "Thus, great caution is advised when releasing mantises for pest control."

While many gardeners may feel a biological pest-management solution is better than a chemical one, recent studies have shown that the indiscriminate nature of a mantises' predatory patterns render their value in this realm to be negligible. And now the threat to local birdlife has been quantified, there is no good reason to recruit this insect into your garden.

So next time you see one of these calm, stately insects sitting meditatively in your garden just remember that if you were a small hummingbird, it would crush your neck and eat your brain in an instant.

The team's study was published in The Wilson Journal of Ornithology.

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