Vocal Cues to Identity: Pied Babblers Produce Individually Distinct But Not Stable Loud Calls

Abstract

The ability to identify social partners can play a key role in the coordination of social behaviours in group‐living animals. Coordinating social behaviours over long distances becomes problematic, as cues to identity are often limited to one or two sensory modalities. This limitation can often select for strong individuality in those cues used for long‐distance communication. Pied babblers, Turdoides bicolor, produce a number of different types of ‘loud calls’ which are frequently used to signal to individuals beyond the range of visual or olfactory pathways of communication. Here, we show that three of these ‘loud call’ types, the v‐shaped chatter, the double note ascending chatter and the atonal chatter, are each individually distinct. We hypothesise that individuality in the three loud call types tested here may represent a possible pathway to social recognition in this species that may have important consequences for social interactions. However, we also found that the atonal chatter was unstable between years suggesting that this particular call type may not be a reliable long‐term indicator to identity which may affect long‐term recognition in this species.

Interactions with conspecific outsiders as drivers of cognitive evolution

“…This alters both the collective threat and the potential threats and opportunities presented to individuals (e.g., from individual roving males seeking breeding opportunities 54 ). Furthermore, information about multiple group members, available from individually distinct scent marks and calls 55,56 , requires more elaborate cognitive processing than that from single outsiders. Additional inferential challenges arise when others shift between 'insider' and 'outsider' status depending on social context (e.g., foraging groups vs. breeding groups).…”

Internal acoustic structuring in pied babbler recruitment cries specifies the form of recruitment

“…A maximum of 2 stimuli were played back in one morning, with at least 2 days break in-between subsequent playback sessions to minimize the risk of habituation to playbacks. Since vocalizations of a group's dominant male were broadcast, and recruitment cries are individually distinct (Humphries et al 2016), stimuli were played back from the location of the dominant male at the time of the playback. This served to prevent reactions to the stimuli based solely on the incongruence between the location of the playback and the location of the dominant male.…”

“…When leading the group through their territory, for example to new foraging or resting sites, males (predominantly the dominant male of a group) produce two types of long and raucous, 'cry-like' structures: 'single-note recruitment cries' (SN cries) and 'double-note recruitment cries' (DN cries) (see also Golabek and Radford (2013) and Humphries et al (2016)). Both cry types start with a wind-up segment which increases in amplitude and grades into repetitions of either A/single-note motifs, or AB/double-note motifs, with both motif types appearing to share the A note, and a B note being added to each A note in the case of double-note motifs (Fig.…”

A field study of auditory sensitivity of the Atlantic puffin, Fratercula arctica

“…Species such as Adélie (Pygoscelis adeliae), king (Aptenodytes patagonicus) and gentoo penguins (P. papua) use their calls to facilitate mate and chick identification as parents or partners return to the noisy colonies. Individuality can be conveyed through certain parameters including call duration, amplitude modulation rates, spectrum bandwidth and distribution of energy among harmonics (Humphries et al, 2016;Jouventin et al, 1999;Kriesell et al, 2018;Ligout et al, 2016;Mathevon, 1997). In Wilson's storm-petrels (Oceanites oceanicus) and several auk species, chicks in poorer condition emit higher frequency calls, and these higher pitched calls also result in the chick receiving increased care, including larger meals (Gladbach et al, 2009;Klenova, 2015).…”