海角大神

How bees give a heads-up when danger is near

A team of researchers from California and China discovered that bees give detailed head butts to their neighbors when wasps are close, the first communication system of its kind among insects. 

Honeybees can warn each other when danger is near, says a new study published Friday in the journal PLOS Biology.

James Nieh, director of the at the University of California, San Diego, teamed up with researchers from the Xishuangbanna Tropical Botanical Garden, Chinese Academy of Science for the study and found that Asian species of honey bees can produce different types of vibrational 鈥渟top signals鈥� when an Asian hornet (their primary predator) is near.

鈥淚f a honeybee is directly attacked or experience something threatening directly either through sight or smell, it will send a one-on-one, one-time signal,鈥� Dr. Nieh tells 海角大神 in a phone interview Tuesday. 鈥淪ensed by feeling the vibration of another bee ramming its head against you,鈥� the bee gets the message that danger is near.聽

There are four different 鈥渇lavors鈥� of stop signals, says Nieh, depending on the size of the threat and the proximity to the nest 鈥� and this is where the study gets especially interesting.聽

Nieh says a similar study on European honeybees already recognized the stop signal. But previously, the researchers believed that it was an inhibitory signal that simply told other bees to stop waggle dancing (or to stop telling other bees where to go for food) when a predator was near. This study, however, proves that honeybees鈥� stop signals are referential.聽

鈥淎fter the European bee study we thought the stop signal was just something to counteract the waggle dance, to say no to that. But the stop signal encodes, in the frequency and duration of the signal, the danger level and the context of predation,鈥� Nieh tells the Monitor. 鈥淭his is quite new and sophisticated. Before, we knew that bees could illicit stop signals, but we didn鈥檛 know it encoded any additional information.鈥澛�

Larger hornets invite stop signals with higher vibrational frequency and hornets close to the nest entrance require signals with longer duration. The worst-case scenario for a colony would be a large wasp close to the nest, inviting the most urgent signal of the four varieties: a long, vibrating pulse. This signal tells nearby bees to stay where they are in the nest to avoid an outside threat.聽

But regardless of what stop signal a bee delivers, the surrounding bees will respond based on the quantity of signals.

鈥淭here is no evidence for a chain reaction, because that could set off an unnecessary panic. Just like if humans believed everything on the Internet, it would create big problems,鈥� Nieh tells the Monitor. The bee will receive the alarm signal, 鈥渂ut she doesn鈥檛 necessarily respond to it until she has received a sufficient number.鈥澛�

And this is why researchers haven鈥檛 understood bee alarm signals for a long time, explains Nieh. The signals don鈥檛 cause the bee the stop moving immediately, but it increases the probability that she will soon.聽

鈥淭hey don鈥檛 immediately respond to every signal because they are assessing the information value, they will believe the danger is more pressing if more than one bee signals them,鈥� says Nieh. 鈥淭he signal is more reliable with more independent sources.鈥澛�

Although such a signal is the first of its kind among insect species, Nieh says his team鈥檚 findings are 鈥渘ot too surprising.鈥澛�

Because the waggle dance can communicate referential, positive information on where food is located, it makes sense that the same insects would have referential communication for negative information such as predator proximity. 聽

鈥淪ophisticated recruitment communication that encodes food location, the waggle dance, is therefore matched with an inhibitory/alarm signal that encodes information about the context of danger and its threat level,鈥� the authors explain in their study. 鈥淭his is the first known example of such a complex alarm system in an insect and demonstrates .鈥�