Bees shriek like alarmed mammals when giant hornets attack

The sounds biologists heard were distressing, distinct, and noisy.

While in Vietnam researching honeybees and giant hornets, scientists recorded the frenetic sounds created by honeybees when giant hornets (an incredible species regrettably and inaccurately dubbed "murder hornet" in the U.S.) attacked their hives. Newly published research in the science journal Royal Society Open Science shows the first-ever documentation of these primal sounds, which reveal how honeybees respond to the threat of the largest wasps in the world. In Asia, it's a dramatic, though natural, wild event.

The sounds, called "antipredator pipes," are harsh calls that are unique from the diversity of other buzzes made by honey bees. These buzzes are like a distressing alarm. 

"They're responding to a pressing threat," Heather Mattila, an associate professor of biological sciences at Wellesley College and an author of the new research, told Mashable. "When these large hornets show up, the bees make these really noticeable anti-predator pipes."

The pipes, which you can hear in the 2013 footage below, are similar to the shrieks or screams from mammals and other social animals in duress. "Animals that live in groups like to share information about predators," noted Mattila. "Groups and flocks work together to keep informed about danger."

It's not just the sound and quality of the "pipes" that were conspicuous. By analyzing over 30,000 recorded communication signals from Vietnam, the biologists found the bees' overall "chatter" jumped eightfold in response to the giant hornets. "When the hornets show up, the bees really amp up that communication," said Mattila.

The bees create this alarm-like buzzing sound (and many others) by vibrating both the muscles in their thorax and their wings. Ultimately, those vibrations pass through the insects' legs, through the hive, and are sensed by other bees. Humans hear these unique sounds; the bees feel them.

And then they react. In response, bees come outside and face the emerging threat. The giant hornets are so large that they're not intimidated by a few bees. But in numbers, the honey bees can sometimes mount a defense. The bees can plaster their hive's entrance with animal dung (essentially using feces as a tool!), which often repels the hornets. Hundreds of bees can also form a "bee ball" around a hornet, wherein they furiously beat their wings and create heat. 

"They'll choke and heat it to death," said Mattila. (Though it's still unknown if the piping drives the bees to defense specifically, or if it's largely an alarm system.) 

The battles between these two insect species might be intense and violent — from the human perspective, anyway — but these are natural happenings in the wild. And in their natural environs, both animals fill important niches, particularly by pollinating plants thus promoting life and biodiversity. Giant hornets have been maligned in recent years, in large part because humans introduced them to the U.S. from Asia (it wasn't the hornet's fault) and the media then attached a wrong-headed name to the animals. But in the hornet's native land, they're an important part of the world.

"Hornets and wasps in general are amazing pollinators," said Mattila. "Insects need to get more respect for the role they play."