Communication breakdown! Signal modality drives the effect of information loss on the behavioral responses of the threatened Great-Billed Seed-Finch, Sporophila maximiliani (Thraupidae: Passeriformes)

Abstract Communication is a central process in animals' interactions and the transmission of information depends on the signal quality. As signals degrade, the resulting loss of information has the potential to increase the ambiguity about the sender’s motivation and status. Thus, the information loss can generate in the receptor a state of motivational conflict and increases the aggressiveness as a coping strategy. We tested whether the information loss affects the behavioral response of Sporophila maximilianiusing (i) a playback experiment, to simulate an acoustic signal, and (ii) a mirror experiment, to simulate a visual signal. We found that a greater degradation of the acoustic signal induced in males’ calls a modulation from lower to higher frequencies, indicating a fear state. Conversely, the degradation of visual signal resulted in an equally high emission of displacement activity in relation to total visual information context, showing no effect of the signal interference. Also, we detected that an increase in the background noise, more than the loss of information, resulted in an increase of the emission of displacement activities and calls of lower frequency, indicating stressful and aggressive states, respectively. So, the response of S. maximiliani to information interference was modulated by the signal modality. The great interference in acoustic signals results in a fear state due to the ambiguity of the interaction context, suggesting that a partially comprehensible signal is more harmful than a totally degraded one. The emission of maintenance behaviors as displacement activities is an indicator of the higher stress endured by the individuals exposed to visual signals, independent of interferences on signal quality. Furthermore, the negative effect of artificial environmental noise can be high, suggesting some level of neophobia in S. maximiliani.