Individual recognition during bouts of antiphonal calling in common marmosets

Abstract

Many vocalizations are encoded with a diversity of acoustic information about the signal producer. Amongst this information content are social categories related to the identity of the caller that are important for determining if and how a signal receiver may interact with that individual. Here, we employed a novel playback method in common marmosets (Callithrix jacchus) to test individual recognition during bouts of antiphonal calling. These experiments utilized custom, interactive playback software that effectively engaged subjects in antiphonal calling using vocalizations produced by a single individual and presented 'probe' vocalization stimuli representing a different individual at specific points within bouts of calling. The aim here was to test whether marmosets would recognize that the probe stimulus was a phee call produced by a different individual. Data indicated that marmosets were able to detect the change in caller identity; subjects produced significantly fewer antiphonal call responses to probe than control stimuli and, in some conditions, exhibited a shorter latency to produce the vocal response. These data suggest that marmosets recognize the identity of the individual during bouts of antiphonal calling. Furthermore, these results provide a methodological foundation for implementing the probe playback procedure to examine a broader range of social categorization during vocal interactions.

Figure 1

(a) Spectrogram showing an antiphonal calling bout. Marmoset 1 is shown above, while Marmoset 2 is shown below. The vocalizations depicted in the spectrogram are common marmoset phee calls. (b) Schematic drawing of the probe playback procedure. M represents the phee calls produced by the subject marmoset. PB represents the phee call stimuli presented by the software. The ‘probe/control’ stimulus is represented as a white colored phee call. That time period is shaded in dark grey. The response period is shaded in light grey. We measured both whether subjects produced an antiphonal call response (y/n) and, if a response did occur, the latency to call production.

Figure 2

Results from ‘Unfamiliar’ probe experiment. (a) Bar graph plots the mean (s.e) percent of antiphonal calls produced in response to probe [blue] and control [black] stimuli for both test conditions combined. (b) Plots the mean (s.e.) latency to respond in seconds for probe [blue] and control [black] stimuli for both test conditions combined. (c) Bar graphs plot the mean (s.e.) percent of antiphonal calls produced in response to probe [red] and control [black] stimuli in each of the individual test conditions: ‘Between-sex’ is shown on the left and ‘Within-sex’ is shown on the right. ** indicates statistical significance.

Figure 3

Results from ‘Familiar’ probe experiment. The column on the left plots the mean (s.e.) antiphonal call responses in bar graphs. The column to the right plots the mean (s.e.) antiphonal response latency in error bars. [a:b] Plots the overall data. Probe stimulus data are shown in blue, while control data are shown in black. [c:d] Plots data for Condition 1: Male Stimuli. Probe stimulus data are shown in red and control data in black. [e:f] Plots data for Condition 2: Female Stimuli. Probe stimulus data are shown in red and control data in black. ** indicates statistical significance.