Follow the leader? Orange-fronted conures eavesdrop on conspecific vocal performance and utilise it in social decisions

Abstract

Animals regularly use social information to make fitness-relevant decisions. Particularly in social interactions, social information can reduce uncertainty about the relative quality of conspecifics, thus optimising decisions on with whom and how to interact. One important resource for individuals living in social environments is the production of information by signalling conspecifics. Recent research has suggested that some species of parrots engage in affiliative contact call matching and that these interactions may be available to conspecific unintended receivers. However, it remains unclear what information third parties may gain from contact call matching and how it can be utilised during flock decisions. Here, using a combined choice and playback experiment, we investigated the flock fusion choices and vocal behaviour of a social parrot species, the orange-fronted conure (Eupsittula canicularis), to a contact call matching interaction between two individuals of different sexes and with different vocal roles. Our results revealed that orange-fronted conures chose to follow vocal leaders more often than vocal followers during fusions. Furthermore, flocks responded with higher call rates and matched the stimulus calls closer when subsequently choosing a vocal leader. Interestingly, orange-fronted conures also showed higher contact call rates and closer matches when choosing males over females. These results suggest that paying attention to conspecific contact call interactions can provide individuals with social information that can be utilised during fission and fusion events, significantly influencing the social dynamics of orange-fronted conures.

Fig 1. Schematic overview of the experimental speaker setup.

Note that the schematic overview is not drawn to scale.

Fig 2. Effect of fusion type on response rate.

LSMean (± SE) contact call response rate emitted by focal flocks during the interaction and choice phase of (A) male-male and (B) male-female trials where flocks made partial or complete fusions with a stimulus individual. Significant pairwise comparisons are indicated with asterisks.

Fig 3. Effect of vocal role and sex on response rate.

LSMean (± SE) contact call response rate emitted by focal flocks during the (A) interaction and (B) choice phase of male-male trials where flocks chose the follower or leader, and during the (C) interaction and (D) choice phase of male-female trials where flocks chose a male or female follower or leader. Significant selected pairwise comparisons are indicated with asterisks.

Fig 4. Effect of fusion type on stimulus-response similarity.

LSMean (± SE) spectrographic cross-correlation (SPCC) similarity between stimulus calls and focal flock responses emitted during the interaction and choice phase of (A) male-male and (B) male-female trials that resulted in partial and complete fusions with a stimulus individual. Significant pairwise comparisons are indicated with asterisks.

Fig 5. Effect of chosen vocal role on stimulus-response similarity.

LSMean (± SE) spectrographic cross-correlation (SPCC) similarity between stimulus calls and focal flock responses emitted during the interaction and choice phase of (A) male-male trials and (B) male-female trials. The figure shows the difference between leaders and followers that were chosen by focal flocks. Significant selected pairwise comparisons are indicated with asterisks.

Fig 6. Effect of chosen sex on stimulus-response similarity.

LSMean (± SE) spectrographic cross-correlation (SPCC) similarity between stimulus calls and focal flock responses emitted during the interaction and choice phase of male-female trials. The figure shows the difference between males and females that were chosen by focal flocks. Significant selected pairwise comparisons are indicated with asterisks.

Fig 7. Effect of vocal role and sex on stimulus-response similarity.

LSMean (± SE) spectrographic cross-correlation (SPCC) similarity between stimulus calls and focal flock responses emitted during the interaction phase of male-female trials. The figure shows the difference between leaders and followers of both sexes. Significant selected pairwise comparisons are indicated with asterisks.