Eastern Honeybees Gung-Ho for Dung
(Inside Science) -- For the first time, scientists have clear evidence that honeybees can use tools to fend off giant hornet attacks, a new study finds. Their tool of choice: balls of dung.
Scientists studying eastern honeybees (Apis cerana) heard accounts from a beekeeper in Vietnam of times he watched bees collecting water buffalo dung. He suggested the bees might use the dung to make the mysterious spots he and other beekeepers saw around hive entrances after attacks by giant hornets (Vespa soror).
"That's really surprising, since honeybees are known for their cleanliness -- they're neat freaks," said study lead author Heather Mattila, a honeybee biologist at Wellesley College in Massachusetts. "They don't like a mess in their colonies, since their hives are warm and humid, a great place for things to spoil and infections to take hold."
Field observations and video monitoring confirmed that worker bees were carrying dung back to their colonies and dabbing it around hive entrances. Such "fecal spotting" increased after giant hornets attacked these colonies, or after the hives were exposed to secretions from the glands the giant hornets use to mark nests for attacks.
The researchers found giant hornets were less likely to land on nest entrances with large numbers of fecal spots, and they spent 94% less time chewing at the entrances if they did land. This suggests that some as-yet-unknown compound in the feces may repel such intruders, or mask the chemical markers they use to tag colonies for an assault.
Giant hornets can launch group attacks on hives that can quickly destroy entire colonies. Previous research found eastern honeybees have evolved a variety of strategies to deter such attacks, such as enveloping intruders in a ball of bees until they overheat, or collectively executing carefully timed shimmering of their wings to confuse predators. These new findings are not only the first known instance of tool use in bees, but also the first example of bees foraging for any solid material besides plant matter.
The researchers detailed their results online Dec. 9 in the journal PLOS ONE.
Using microphones placed in hives, the scientists are now exploring how these bees use sounds and vibrations to respond to giant hornet attacks.