Dwarf mongoose alarm calls: investigating a complex non-human animal call

Abstract

Communication plays a vital role in the social lives of many species and varies greatly in complexity. One possible way to increase communicative complexity is by combining signals into longer sequences, which has been proposed as a mechanism allowing species with a limited repertoire to increase their communicative output. In mammals, most studies on combinatoriality have focused on vocal communication in non-human primates. Here, we investigated a potential combination of alarm calls in the dwarf mongoose ( Helogale parvula ), a non-primate mammal. Acoustic analyses and playback experiments with a wild population suggest: (i) that dwarf mongooses produce a complex call type (T 3 ) which, at least at the surface level, seems to comprise units that are not functionally different to two meaningful alarm calls (aerial and terrestrial); and (ii) that this T 3 call functions as a general alarm, produced in response to a wide range of threats. Using a novel approach, we further explored multiple interpretations of the T 3 call based on the information content of the apparent comprising calls and how they are combined. We also considered an alternative, non-combinatorial interpretation that frames T 3 as the origin, rather than the product, of the individual alarm calls. This study complements previous knowledge of vocal combinatoriality in non-primate mammals and introduces an approach that could facilitate comparisons between different animal and human communication systems.

Lesser spot-nosed monkeys coordinate alarm call production with associated Campbell’s monkeys

“…We carried out a permutated discriminant function analysis (pDFA; R function by Roger Mundry, based on the lda function of the 'MASS' R package version 7.5-53; Venables and Ripley 2002;Mundry and Sommer 2007) to check the classification in the three attributed call types (i.e., 'kroo', 'tcha', 'kow') with call type as test variable and the trial ID as control factor (pDFA1). The pDFA allows to control for the non-independence of data due to repeated measurements (i.e., control factor), unlike conventional DFAs, and is now commonly used for acoustic analyses of animal vocal repertoires (e.g., Collier et al 2020;Keenan et al 2020). We also analysed inter-individual variation by running another pDFA (pDFA2) on N = 6 different males (i.e., six different trials, selected based on home range estimates and time of recording; see Online Resource 1, Table S4), who produced a minimum of 22 'kroo' calls of good acoustic quality (range: 22-55 calls).…”

“…General alarm calls have already been described for other primate and non-primate species, such as Gunnison's prairie dogs (Cynomys gunnisoni) 'bark' calls for different predator types (Loughry et al 2019) or woolly monkey (Lagothrix lagothricha) 'eolk' calls to predatory and non-predatory disturbances (Casamitjana 2002). Different functional explanations have been offered for general alarm calls (Dezecache and Berthet 2018), such as providing callers with the option to create a semantic contrast to predator-specific alarm calls, typically aerial alarm calls (e.g., dwarf mongoose (Helogale parvula), Collier et al 2020;putty-nosed monkeys, Price et al 2009), or to issue a behavioural imperative (e.g., 'hide!') to warn other group members or, in exceptional cases, deceptively, to gain access to food (Flower et al 2014).…”

From collocations to call-ocations: using linguistic methods to quantify animal call combinations

“…Over the last 20 years, there has been a growing interest into the combinatorial abilities of animals, namely the propensity to sequence context-specific calls (i.e. meaning-bearing units, see Suzuki and Zuberbühler 2019 ) into larger potentially meaningful structures (Arnold and Zuberbühler 2006 ; Ouattara et al 2009 ; Engesser et al 2016 ; Suzuki et al 2016 ; Collier et al 2020 ). Combinatoriality is one mechanism that can increase the expressive potential of a finite vocal repertoire (Nowak et al 2000 ).…”

From collocations to call-ocations: using linguistic methods to quantify animal call combinations

“…Combinatoriality is one mechanism that can increase the expressive potential of a finite vocal repertoire. It therefore provides important comparative insights into the complexity of animal vocal systems and the selective pressures such systems have been exposed to (Collier et al, 2020). These data also hold great promise in furthering our understanding of the similarities between animal communication and human language given that, for many years, it was assumed that the systematic concatenation of meaning-bearing units (i.e., syntax) was a phenomenon unique to language (Hurford, 2012).…”

“…Over the last 20 years there has been growing interest into the combinatorial abilities of animals, namely the propensity to sequence context-specific calls (i.e. meaning-bearing units, see (Suzuki & Zuberbühler, 2019) into larger potentially meaningful structures (Arnold & Zuberbühler, 2006; Collier et al, 2020; Engesser, Ridley, & Townsend, 2016; Ouattara, Lemasson, & Zuberbühler, 2009; Suzuki, Wheatcroft, & Griesser, 2016). Combinatoriality is one mechanism that can increase the expressive potential of a finite vocal repertoire.…”