Sounding the alarm: How honey bees alert their hive to attacks by giant 'murder' hornets

A Vietnamese honey bee hive is attacked by giant "murder" hornets. Credit: Heather Mattila/Wellesley College
The unique sounds honeybees (Apis Cerana) make to warn their hive members when they are threatened by giant "murder"hornets have been recorded for the first time. Heather Mattila, an associate professor of biological sciences at Wellesley College, and her collaborators have been studying these signals. Their findings were published in Royal Society Open Science.

Mattila and a team of international researchers discovered that honey bees sound an alarm to each other to protect themselves from attacks by giant beets (Vespa Soror), which can decimate entire colonies. When giant hornets are within their hive, bees emit distress signals, including antipredator pipes, at a fast pace. Mattila felt the chills upon hearing it. She said that the pipes have many similarities to mammalian alarm signals. "They are instantly recognizable as warning of danger." "It feels like a universal experience."

The sounds of antipredator pipes differ from those previously recorded in colonies, such as "hisses" or "stop signals". These new signals are loud and irregular and have a frequency shift that is similar to the panic calls meerkats, birds, and primates make to avoid predators. The signals alert the hive of the imminent arrival of giant beets. They also cause an increase in the number of bees at the entrance. This is the beginning of their defense actions. These include spreading animal dung around the colony entrances to repel them (the first documented use by bees of tools) and creating bee balls to kill the attacking hornets together.

Mattila and her colleagues have been studying interactions between giant beets and Asian honeybees in Vietnam for more than seven years. They collect audio and video recordings from hornet attacks in the apiaries of local beekeepers. Over 1,300 minutes of monitoring, microphones installed in hives recorded almost 30,000 signals from bees.

A Vietnamese bee hive is attacked by giant "murder" hornets. Credit: Heather Mattila/Wellesley College

Recordings of colonies under attack by giant hornets was noisy and fast, while recordings of the control colonies were quieter and more peaceful. Bees' chatter increased eightfold when giant hornets attacked, compared to when there weren't any threats. The researchers stated that bees communicate with each other in good and bad times, but it is especially important to exchange antipredator signals during critical moments, when it is necessary to rally workers for colony defense.

Gard Otis is a colleague of Mattila and a professor emeritus at the School of Environmental Sciences of the University of Guelph’s Ontario Agricultural College. "This research shows just how complex signals produced Asian hivebees can be." We feel that we have only scratched the surface of their communication. There is so much more to learn.

The team observed that bees raise their abdomens when they make antipredator pipe, buzz their wings and run frantically while revealing their pheromone producing Nasonov gland. It is clear that bees produce multiple types information in order to attract their nestmates' attention. Mattila intends to continue investigating this behavior.

Continue reading Honey bees fight giant hornets using animal dung

More information: Giant Hornet (Vespa Soror) attacks trigger frenetic Antipredator Signalling in Honey Bee (Apis Cerana) colonies. Royal Society Open Science (2021). Journal information: Royal Society Open Science Giant hornet (Vespa soror) attacks trigger frenetic antipredator signalling in honey bee (Apis cerana) colonies,(2021). DOI: 10.1098/rsos.211215