Call order within vocal sequences of meerkats contains temporary contextual and individual information

Abstract

Background The ability to recombine smaller units to produce infinite structures of higher-order phrases is unique to human language, yet evidence of animals to combine multiple acoustic units into meaningful combinations increases constantly. Despite increasing evidence for meaningful call combinations across contexts, little attention has been paid to the potential role of temporal variation of call type composition in longer vocal sequences in conveying information about subtle changes in the environment or individual differences. Here, we investigated the composition and information content of sentinel call sequences in meerkats (Suricata suricatta). While being on sentinel guard, a coordinated vigilance behaviour, meerkats produce long sequences composed of six distinct sentinel call types and alarm calls. We analysed recordings of sentinels to test if the order of the call types is graded and whether they contain additional group-, individual-, age- or sex-specific vocal signatures. Results Our results confirmed that the six distinct types of sentinel calls in addition to alarm calls were produced in a highly graded way, likely referring to changes in the perceived predation risk. Transitions between call types one step up or down the a priory assumed gradation were over-represented, while transitions over two or three steps were significantly under-represented. Analysing sequence similarity within and between groups and individuals demonstrated that sequences composed of the most commonly emitted sentinel call types showed high within-individual consistency whereby adults and females had higher consistency scores than subadults and males respectively. Conclusions We present a novel type of combinatoriality where the order of the call types contains temporary contextual information, and also relates to the identity of the caller. By combining different call types in a graded way over long periods, meerkats constantly convey meaningful information about subtle changes in the external environment, while at the same time the temporal pattern of the distinct call types contains stable information about caller identity. Our study demonstrates how complex animal call sequences can be described by simple rules, in this case gradation across acoustically distinct, but functionally related call types, combined with individual-specific call patterns.

Animal linguistics: Exploring referentiality and compositionality in bird calls

“…Although bird songs can be structurally complex, their meaning is considered to be simple, with song phrases generally having certain functions, notably facilitating mate attraction, territorial defense, or both (Catchpole & Slater, 2008; Podos et al, 2004). Combinations of sound elements are widely detected in non‐human animals, including bats (Bohn, Smarsh, & Smotherman, 2013), mice (Chabout, Sarkar, Dunson, & Jarvis, 2015), mongooses (Fitch, 2012; Jansen, Cant, & Manser, 2012; Rauber, Kranstauber, & Manser, 2020), cetaceans (Payne & McVay, 1971; Mercedo, Herman, & Pack 2005), gibbons (Clarke, Reichard, & Zuberbühler, 2006) and gorillas (Hedwig, Mundry, Robbins, & Boesch, 2015). However, most of these vocal sequences have been considered as holistic sequences, the meanings of which are conveyed by the overall sequences, and consequently, the sequence is not considered as a compositional expression.…”

“The song remains the same”: not really! Vocal flexibility in the song of the indris

“…This is in line with findings from human and non-human species on the creative use of vocalizations to solve problems: for example, in human collaborative problem-solving, utterances to elicit and maintain interactions, thus increasing the social bond, were frequently observed (Johnson and Johnson 1986 ; Yokozuka et al 2021 ). Chimpanzees have the necessary socio-cognitive skills to naturally develop a simple communicative strategy to ensure coordination in a collaborative task (Melis and Tomasello 2019 ). Bottlenose dolphins are well-known for cooperating extensively in the wild and can adjust vocal signals to facilitate the successful execution of coordinated, cooperative actions (King et al 2021 ).…”

Evidence for vocal signatures and voice-prints in a wild parrot

“…However, maintaining multiple signals of identity is cognitively demanding for signallers and receivers to remember; consequently, this strategy is likely constrained to species with either small vocal repertoires or small group sizes (Elie and Theunissen 2018). The second solution is to combine a single identity call with the other call types in a sequence (Rauber, Kranstauber, and Manser 2020). The cognitive demands of this strategy are much lower, and if flexibly deployed, it potentially allows individuals to signal identity in contexts where recognition is beneficial and hide identity in other contexts.…”