A comparison of individual distinctiveness in three vocalizations of the dwarf mongoose (Helogale parvula)

Abstract

Individual specificity can be found in the vocalizations of many avian and mammalian species. However, it is often difficult to determine whether these vocal cues to identity rise from "unselected" individual differences in vocal morphology or whether they have been accentuated by selection for the purposes of advertising caller identity. By comparing the level of acoustic individuality of different vocalizations within the repertoire of a single species, it is possible to ascertain whether selection for individual recognition has modified the vocal cues to identity in particular contexts. We used discriminant function analyses to determine the level of accuracy with which calls could be classified to the correct individual caller, for three dwarf mongoose (Helogale parvula) vocalizations: contact, snake, and isolation calls. These calls were similar in acoustic structure but divergent in context and function. We found that all three call types showed individual specificity but levels varied with call type (increasing from snake to contact to isolation call). The individual distinctiveness of each call type appeared to be directly related to the degree of benefit that signalers were likely to accrue from advertising their identity within that call context. We conclude that dwarf mongoose signalers have undergone selection to facilitate vocal individual recognition, particularly in relation to the species' isolation call. K E Y W O R D Sacoustic analysis, contact calls, dwarf mongoose, Helogale parvula, individual specificity, isolation calls, snake calls

Experimental evidence for delayed contingent cooperation among wild dwarf mongooses

“…The maximum amplitude of the two call types was measured using a Sound Level Meter (Metrel UK). Previous work has shown that dwarf mongoose close calls are individually specific with respect to the peak frequency of the fundamental ( 58 , 63 ). Surveillance calls are also likely to be individually distinct since they are similar in this acoustic characteristic to close calls—we found no significant difference between the means (Wilcoxon signed-rank test: V = 0.75, n = 40 individuals, P = 0.459, mean ± SE frequency difference = 69 ± 9.8 Hz) nor the CVs (asymptotic test: P = 0.754, close calls: range = 761–1,751 Hz, CV = 17%; surveillance calls: range = 890–1,794 Hz, CV = 18%) (see also ref.…”

Individual distinctiveness across call types of the southern white rhinoceros (Ceratotherium simum simum)

“…Arousal and anxiety are known to reduce saliva production and to increase muscle tension in mammals ( Kirchhübel et al 2011 ). In dwarf mongooses ( Helogale parvula ), it was shown that calls emitted during high-arousal situations show less individual variation as compared to calls emitted during low-arousal states ( Rubow et al 2018 ), whereas in domestic kittens ( Felis catus ) no difference in the level of individual distinctiveness was found between high- and low-arousal contexts ( Scheumann et al 2012 ). The southern white rhinoceros uttered two call types during aggressive interactions.…”

“… tonal PIC, DFA Howl > Bark – – YES Bark high arousal directed ?? noisy Dwarf mongoose ( Helogale parvula ) Rubow et al 2018 Contact call intragroup social call directed - affiliative close tonal PIC, DFA+ Isolation call > Contact > Snake call YES PART. – Snake call alarm call general intermediate tonal Isolation call Isolation, separation directed far tonal Domestic dog ( Canis familiaris ) Yin and McCowan 2004 Disturbance bark disturbance general far noisy DFA Isolation bark = Play bark > Disturbance bark YES NO YES Isolation bark isolation directed mixed tonal …”

“…Thus, vocalization can encode the identity of the individual, which provides the basis for vocal individual discrimination. Individual discrimination is important for regulating social relationships to govern cohesion, attraction, and avoidance, among conspecifics ( August and Anderson 1987 ; Ehret 2006 ) such as mother–infant reunions, support of specific group members, or avoidance of inbreeding (e.g., Phillips and Stirling 2000 ; Torriani et al 2006 ; Wittig et al 2007 ; Müller and Manser 2008 ; Bouchet et al 2012 ; Kessler et al 2012 ; Rubow et al 2018 ). It therefore can be assumed that the more complex social organization will favor individual distinctiveness in call types.…”

“… Lemasson and Hausberger (2011) expanded the social function hypothesis and proposed that individual distinctiveness was highest in calls related to affiliative contexts, intermediate in calls related to agonistic contexts, and lowest in calls related to general activities or directed to the whole group. Evidence for the social function hypothesis was found in several mammalian orders such as Primates (Chacma baboon— Rendall et al 2009 ; rhesus monkeys— Rendall et al 1998 ; red-capped mangabeys— Bouchet et al 2012 , 2013 ), Carnivora (dwarf mongoose— Rubow et al 2018 ; domestic dog— Yin and McCowan 2004 ; giant otter— Mumm et al 2014 ), and Rodentia (African woodland dormouse— Ancillotto and Russo 2016 ).…”