Asian giant hornets and their similarly formidable relatives the Asian hornet can lay waste to entire honey bee hives in a matter of hours. If you’ve seen video of the marauding hornets decapitating honeybees in droves, then it’s hard to imagine what chance the comparatively benign buzzers might have against such a foe.
The worry that honey bees seem helpless against these vicious attacks is justified in North America and Europe, where members of the menacing Vespa family, that includes the infamous giant hornet, have begun to invade unsuspecting hives.
But in their native East Asia, these bee-killing hornets don’t have it so easy. In Japan, honey bees, which have evolved alongside these huge wasps for millennia, lure hornet scouts inside their hive and then cook them alive in a frenzy of vibrating bee bodies. Now, new research documents an even more unlikely defense strategy from the Asian honey bee (Apis cerana): smearing the hive entrances with poop, reports Katherine J. Wu for the New York Times.
Heather Mattila at Wellesley College in Massachusetts, who led the study, tells Damian Carrington of the Guardian she was “shocked [by the use of faeces] because bees have such a good reputation for being clean. They have hot, wet, permanent homes that are a great place for disease to grow and are filled with babies and food.”
Writing in the journal PLOS One, the researchers report that honey bees in Southeast Asia cover the entrances of their hives in bird and buffalo dung. Members of the colony fly around collecting the feces with their mouths and apply it to the hive’s front door in "spots," reports Matt Simon for Wired. The researchers found the hives with the most poo spots effectively warded off the Asian hornet (Vespa soror).
Per the Times, researchers aren’t totally sure about the active ingredient of the bees’ malodorous home decor in terms of wasp repellent. Mattila says it may be that certain plant compounds lurking in the feces may repel the hornets or that these insect predators are simply warded off by the unwelcome smell and a desire for a clean meal. Still another hypothesis is that the smell of poop masks the colony’s normally attractive odor, serving as a kind of olfactory cloaking device—that’s right, stealth poo.
Experiments bore out the efficacy of the unorthodox home defense tactic: hornets spent less than half the time at nest entrances with heavy fecal spotting than they did checking out clean hives, and 94 percent less time trying to chew through the hive’s exterior, according to the Guardian. The researchers even found that when they applied a scent compound used by the hornets to mark bee hives for slaughter, the bees swiftly daubed the entrances with a fresh coat of excrement.
Per the Guardian, the researchers suggest the behavior may be common among bees in Vietnam, Thailand, Bhutan, Nepal and parts of China.