Blue jays like to use false alarm calls to steal food from rival groups. But as an experiment has now revealed, the corvids have developed a protective mechanism against such deceptions: They only react quickly and unreservedly to the warning calls if they come from members of their own group. On the other hand, they largely ignore the calls from hehers from neighboring territories.
Although our language is mainly used to exchange reliable information, people sometimes deceive and lie to one another. We often use this particular form of communication for fun or for gain. But if a person overcomes it, their own trustworthiness can be lost. “If you are repeatedly lied to by someone, you will most likely quickly stop trusting that person,” explains Michael Griesser from the University of Zurich.
How do blue jays protect themselves from deception?
But do animals also judge the trustworthiness of a communication partner on the basis of personal experiences with them or do they use other mechanisms to protect themselves from deception? Scientists working with Filipe Cunha from the University of Zurich have investigated these questions. To do this, they chose the common jay (Perisoreus infaustus) as animal test objects. These territorial corvids living in family groups have a wide repertoire of warning calls with which they warn each other of dangers and in particular of their worst predator, the hawk.
But the jays also use these warning calls to deceive competing conspecifics: They use the hawk warning call to induce the members of another group to flee and thus get their food. “In the animal kingdom one often finds the phenomenon that warning calls are used to deceive, because there is a high risk for the recipient of the wrong information to ignore it,” explains Cunha.
To find out how blue jays deal with this type of deception, the researchers examined a population of wild blue jays in northern Sweden. With the help of food, they lured experienced birds to a feeding place. As soon as a single animal visited the feeding place, previously recorded sequences of the typical warning call were played to it over the loudspeaker. These came either from former group members with whom the animals had lived two to five years ago, from birds from neighboring territories or from individuals with whom the visitor to the feeding place had not previously had any contact. Using video recordings, Cunha and his colleagues determined how quickly and for how long the birds fled.
Jays only trust their group members
It turned out that the badger jays recognized who the call came from and were able to use this social information to protect themselves from potential deception. “Our results show that bad jays react differently to the playing of warning calls, depending on the social relationship with the caller,” the scientists said. The corvids observed showed an immediate and long-lasting escape reaction only to the warning calls from former group members. After such calls, the animals took an average of 0.3 seconds to flee and only came back to the feeding station after about eight minutes. This reaction was solely dependent on whether the caller had belonged to their own group. The length of time for which the corvids observed had previously lived with these conspecifics, or their relationship to the former group members, played no role
Warning calls from neighbors or unknown individuals were largely ignored and led to slower reactions and faster return to the feeding place. In both cases, the corvids only fled an average of more than fifteen seconds after the warning call and came back to the food after around three minutes. “Bad luck jars have a very simple rule to avoid deception: They only trust calls from group members, that is, cooperation partners,” explains Cunha’s colleague Michael Griesser. “Just knowing the caller, which also applies to the neighbors, is not enough.”
The benefits are greater than the risks
But why has this mechanism developed to protect against deception in the bad luck tugs, when any ignored warning call could possibly cost the animals their lives? In fact, this selective reaction increases the fitness of the animals more than if they responded to every warning call from their neighbors and strangers. Because false warnings from competing conspecifics occur about every fifth day. The actual threat from a hawk, on the other hand, only occurs around every 8.5 months. “It is therefore very unlikely that hawk calls from neighbors would indicate a living hawk,” explain Cunha and his colleagues.
Source: University of Konstanz, Article: Science Advances, doi: 10.1126 / sciadv.aba2862