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 signalling level according to the rival’s behaviour. 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 behavioural 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 vocalisations are costly, this suggests that such behavioural strategies are honest. Our results highlight the importance of real-time signalling adjustment in communication processes over resource competition and emphasize the power of using interactive playback settings to investigate conflict resolution in animals.
Highlights
Conspecifics compete over limited resources, such as territories, mates, or food (McGregor, 2005) by either fighting or communicating (Parker, 1974; Maynard Smith, 1982)
The central goal of negotiation is to limit aggressive behaviors, which may lead to serious or lethal injuries. Such a term has been mostly used in the context of humans that bargain for resources (Binmore, 2010), this concept has been applied to animals especially in a context of long-term relationship between opponents (McNamara et al, 1999; Johnstone and Roulin, 2003; Johnstone and Hinde, 2006; Patricelli et al, 2011; Sirot, 2012)
While humans use various negotiation tactics by modulating gestures, words, and voice, it is not fully clear whether this process is common in animals and how it exactly occurs (Pika and Frohlich, 2019)
Summary
Conspecifics compete over limited resources, such as territories, mates, or food (McGregor, 2005) by either fighting or communicating (Parker, 1974; Maynard Smith, 1982). The negotiation in barn owl nestlings is an interactive process through progressive step-like series of variations in call parameters ending when an individual becomes vocally dominant by emitting more and longer calls or even silencing the opponents. We predicted that these strategies are most effective to dominate the negotiation by inducing a sibling to progressively emit shorter calls at a lower rate These strategies could be considered as signals by themselves and should entail costs in order to prevent dishonesty and be evolutionary stable (Zahavi, 1974; Grafen, 1990; Maynard Smith and Harper, 2003; Searcy and Nowicki, 2005). This setting allowed us to determine whether the most effective strategies to prevail in negotiation are the costliest in the sense that the playback emits more and/or longer calls
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