Praying mantises released for pest control are hunting hummingbirds

New research documents that mantises worldwide are eating small birds; in the US, invasive mantis species are devouring hummingbirds.

If the headline weren't startling enough, the photos are even worse. There is an order to predators and prey that feels normal – like, birds eat insects. And when the script it flipped it can feel a bit horror-movie premise; which is why the idea of praying mantises stalking the hummingbird feeder for their next meal seems oh so unnerving.

But sure enough, a new study published in the Wilson Journal of Ornithology finds that mantises feeding on birds is a global pattern.

We already knew that praying mantises – so beautiful and fascinating – are carnivorous insects, generally subsiding on arthropods such as insects or spiders (and their mates after sex, but that's a different story). On occasion they have been known to eat smaller vertebrates such as frogs, lizards, salamanders or snakes. Stalking birds, however, isn't usually listed by scientists as part of the mantis menu plan.

The research was conducted by zoologists from Switzerland and the U.S. The team reviewed many types of bird-eating mantises, documenting 12 species and nine genera shown preying on small birds in the wild. And the extraordinary behavior was found in 13 different countries and every continent except Antarctica. As for the victims, they came from 24 different species and 14 families.

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

But aside from the remarkable discovery itself, what may be even more unsettling is a part we humans have unwittingly played. Of the 147 documented cases, more than 70 percent occurred in the U.S., where praying mantises grab hummingbirds from feeders and as they're flitting about on garden flowers. (Most of the avian victims are hummingbirds, with an especial preference for ruby-throated hummingbird (Archilochus colubris).)

As it turns out, decades ago alien species of mantises like the European mantis (Mantis religiosa) and the Chinese mantis (Tenodera sinensis) became popular for biological pest control. In theory, hiring insects to eat the pests is a great idea – in practice, when non-native insects are introduced, all heck can break loose. These imported mantis species "now constitute a new potential threat to hummingbirds and small passerine birds," say the authors, who conclude: "Our compilation suggests that praying mantises frequently prey on hummingbirds in gardens in North America; therefore, we suggest caution in use of large-sized mantids, particularly non-native mantids, in gardens for insect pest control."

Native insects eating pests is a great thing; invasive insects eating native birds starts edging into the world-gone-wrong realm. Before introducing new species into your garden, do some research – just because you can buy pest-controlling mantises by the hundreds on Amazon doesn't mean you won't be putting your beautiful hummingbirds at risk.