Is the urgency message encoded in heterospecific alarm calls perceived by domestic chickens?

Vertebrate alarm calls can signal danger, and often encode information about predator proximity. Some species of birds alter the number of notes of their alarm calls to reflect urgency, with high-urgency alarm calls having more notes than low-urgency calls. Not only do individuals perceive the urgency message encoded in the alarm calls of conspecifics, but also in the alarm calls given by heterospecifics (sympatric and allopatric species). Yet, although well studied in wild species, the capacity to use heterospecific graded alarm call systems has not been investigated in domestic animals. Domestication may have altered the perceptual and communicative abilities of domestic species because they are less threatened by predators. Using playbacks conducted on domestic naked neck chickens (Gallus gallus domesticus) in France, we tested whether this species is able to decode information about urgency in alarm calls produced by a sympatric species; the common chaffinch (Fringilla coelebs), and by an allopatric species; the Australian magpie (Cracticus tibicen). We found the latency to resume foraging behaviour was higher after the high-urgency call playbacks than the low-urgency call playbacks, suggesting that the urgency encoded in heterospecific calls was perceived by chickens. However, results seem to indicate that the chickens are not able to discriminate between alarm and control (songs) sounds, but simply respond to specific sound characteristics of each playback stimulus. Our results raise some questions about how animals perceive and attend to information provided by heterospecific alarms. We hope this study will encourage future work with domesticated and nondomesticated animals.