The Art of Diplomacy in Vocally Negotiating Barn Owl Siblings

Abstract

To resolve conflicts over limited resources, animals often communicate about their motivation to compete. When signals are transient, the resolution of conflicts may be achieved after an interactive process, with each contestant adjusting its signaling level according to the rival's behavior. Unfortunately, the importance of the real-time signal adjustment in conflict resolution remains understudied, especially using experimental approaches. Here we developed a novel "automatic interactive playback" that interacts real-time with a live individual. It allowed us to experimentally test the efficacy of different behavioral strategies to dominate conflicts in nestling barn owls (Tyto alba). In this species, nestlings vocally negotiate for priority access to the impending food item in the absence of parents. Two opposite vocal strategies were tested for their prospects of success: under the "matching" vs. "mismatching" strategy, the playback behaves in the same vs. opposed way as the nestling, respectively. We evaluated how these two strategies affected the two main negotiation parameters: call duration and call rate. We found that the best strategies to reduce the nestling's vocalizations and hence dominate the negotiation are to match the call duration of the opponent and to mismatch its call rate. However, the latter strategy is the only one that allowed the playback to dominate the vocal interaction by inducing the opponent to become totally silent. Therefore, to prevail in a negotiation session, barn owl nestlings should delay the transmission of signals rather than simultaneously escalate vocalizations as commonly observed in animal competitive interactions. In addition, we showed that matching call duration and mismatching call rate require a larger investment by the playback, in terms of number and duration of calls, than the less effective strategies. Assuming that vocalizations are costly, this suggests that such behavioral strategies are honest. Our results highlight the importance of real-time signaling adjustment in communication processes over resource competition and emphasize the power of using interactive playback settings to investigate conflict resolution in animals.

Acoustic Cooperation: Acoustic Communication Regulates Conflict and Cooperation Within the Family

“…In addition, more empirical studies are clearly needed on a range of species to understand the generality of the patterns highlighted here. Beside their ubiquity in many taxa, acoustic signals are particularly amenable to fine experimental research using playbacks and continuous recordings, including automatic interactive playbacks (Ducouret et al, 2019) and playbacks targeting specific individuals (e.g., Hinde and Kilner, 2007).…”

“…Most remarkably, in the barn owl (Tyto alba), a series of original experiments by Dreiss, Roulin, and collaborators has revealed the vocal negotiation occurring between siblings, before parents bring a single indivisible prey back to the nest (Roulin and Dreiss, 2012). They have shown that owlets challenge each other vocally in an interactive process by adjusting their calls to those of their siblings, either intensifying or reducing begging calls depending on their level of need (Roulin et al, 2009) and their opponents' vocalisations (Ducouret et al, 2019). The most vocal chick in parent's absence is more likely to get the next prey from the parents (Roulin et al, 2009), whilst others refrain from begging to the parents (Dreiss et al, 2010).…”

“…Indeed, acoustic signals can readily indicate individuals' immediate state and perhaps their short-term intentions. In addition, interactive acoustic communication, whereby individuals adjust their vocalisations in response to others' signalling, is especially well-suited for realtime negotiation (e.g., Ducouret et al, 2019). Lastly, unlike other senses, the acoustic (or vibratory) channel allows a sophisticated level of communication and negotiation to occur prenatally, in parent-embryo and embryo-embryo interactions (Mariette and Buchanan, 2019b;Noguera and Velando, 2019).…”

Non-Vocal Behaviors Are More Frequent During the Decisive Negotiation Phases in Barn Owl Siblings

“…Although between two feeding events and in the short-term (e.g., about several minutes) the need for resources of each participant does not vary, the negotiation process is still very dynamic, being sensitive to the social interaction process itself. Accordingly, barn owl siblings adjust their vocal negotiation to one another on a short-term basis, independently of variation in food need, as shown by observational and experimental studies [ 27 , 31 , 32 , 33 ]. The negotiation process between siblings may be similar to human dialogues, with specific turn-taking rules being used to decide when an individual will start or stop calling [ 31 , 32 , 34 ].…”

“…When an individual starts calling, it gradually produces longer but fewer calls per minute. When it “relaxes” and makes shorter calls, with longer pauses, another sibling is likely to interrupt it by emitting short calls and can gradually monopolize the negotiation [ 31 , 32 , 34 ]. By following these turn-taking rules, individuals have the opportunity to alternatively signal their motivation and perceive the motivation of their counterparts, which allows each individual to adequately decide to withdraw from the contest or to pursue competitive interaction [ 31 , 32 , 34 ].…”