Jana Nácarová, Petr Veselý, Thomas Bugnyar
Heterospecific alarm calls are typically found in situations where multiple species
have a common predator. In birds, they are particularly common in mixed mixed-species flocks. In species with highly developed social and cognitive abilities like corvids, there is the potential for differential responses to heterospecific vs. conspecific
calls according to the riskiness of the habitat. We tested the responses of free-ranging
ravens (Corvus corax) to conspecific alarm calls and compared them to heterospecific
alarm calls of jackdaws (Corvus monedula). We observed the proportion of ravens leaving the feeding site after the con-or hetero-specific playback was presented in a situation of low threat (wild boar—Sus scrofa enclosure) and high threat of
predation (wolf—Canis lupus enclosure). We show that ravens responded to conspecific calls more intensively at the wolves than at the wild boar, but the response to conspecific calls was in both enclosures stronger than to the control (great tit—Parus
major song). The response to the heterospecific alarm was also stronger in the wolves’
enclosure, but it did not differ from control in the wild boar enclosure. These findings
suggest that ravens are aware of the meaning of the jackdaw alarm calls, but they
respond to it only in a situation of high predatory threat (wolves are present). In the
wild boar enclosure, the ravens probably consider jackdaws warning against some
other predator, very probably harmless to ravens. This interpretation requires further
testing, as both enclosures differ also in respect to other parameters like food quality
and shelter availability.
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