How do honey bees ward off giant hornets? They use poop, study finds. Here’s how
Most living creatures will do anything to protect their homes and families, no matter how expensive, brave or smelly.
Yes, smelly.
For the first time, honey bees in Asia were spotted buzzing to piles of animal poop, putting heaps of dung in their mouth and decorating the entrances to their hives with the droppings, giving special preference for the more foul-smelling selections from chickens and pigs.
Turns out the gag-worthy gate of poo significantly reduced how long and often deadly giant hornets — cousins to the famed North American “murder hornets” — chewed at or raided honey bee hives, according to new research published Dec. 9 in the journal PLOS One.
Experts call the defensive behavior “fecal spotting.” The researchers aren’t exactly sure why giant hornets are repelled by the poop, but they infer the smell itself could be doing the trick. The odor could also be masking smells released by bees that might attract the invaders.
These hornets, which carry about seven times as much venom in a single sting as an ordinary honey bee, are known to form organized attacks that can wipe out entire colonies, emptying hives of larvae and pupae to feed their own babies.
That’s only after killing most if not all honey bee inhabitants first.
The discovery is also the first time honey bees have been found to intentionally use tools “and the first evidence that they forage for solids that are not derived from plants,” according to the study.
“We documented that hornets were less likely to land on entrances or chew their way into hives when there were more fecal spots around entrances,” study lead author Heather Mattila, a biology professor at Wellesley College in Massachusetts, said in a university news release.
“While further research is needed to determine exactly what properties of animal feces repel the hornets, the barrier the bees create is an effective defense against their attacks — a chemical weapon of sorts.”
Poopy hives to the rescue
Of the 67 beekeepers in Vietnam the researchers surveyed in late August — when giant hornet attacks occur most often — 63 of them reported poop spots splattered on the fronts of their hives, according to the study.
Each beekeeper, who had a median of 15 colonies, reported manure on 74% of their hives.
In their own experiments, the researchers gathered poop from water buffalo, chickens, pigs and cows, and set piles of it near an apiary housing honey bees. By the end of the day, about 150 honey bees were seen visiting the piles and applying the dung around the entrances of their hives.
The team discovered that the hornets spent less than half as much time at nest entrances covered with moderate to heavy amounts of poop than they did at hives with less dung, according to the release.
The invaders also spent “one-tenth” as much time chewing at the entrances, and were less likely to attack on poopy hives in general.
In another follow-up experiment, the researchers collected a chemical pheromone — substances that affect the behaviors of others within a species — from giant hornets and applied them to hives.
As expected, the honey bees were prompted to smother poop on their homes.
North American honey bees and ‘murder hornets’
Unfortunately, North American honey bees haven’t evolved to fend off the similar “murder hornets” that were unintentionally introduced in their region and that have recently been found in Washington state and British Columbia in Canada.
Instead, beekeepers have to take the matter into their own hands by destroying hornets’ nests, standing by hives and swatting individual invaders or relying on climate factors that could limit the hornets’ presence, according to the researchers.
“They haven’t had the opportunity to evolve defences. It’s like going into a war cold,” Mattila said in a news release by the University of Guelph in Canada, where she completed her PhD.
This story was originally published December 10, 2020 at 6:24 PM with the headline "How do honey bees ward off giant hornets? They use poop, study finds. Here’s how."
