Vocal recruitment in dwarf mongooses (Helogale parvula)

Rubow, Janneke (2017-03)

Thesis (MSc)--Stllenbosch University, 2017

Thesis

ENGLISH ABSTRACT: Vocal communication is important in social vertebrates, particularly those for whom dense vegetation obscures visual signals. Vocal signals often convey secondary information to facilitate rapid and appropriate responses. This function is vital in long-distance communication. The long-distance recruitment vocalisations of dwarf mongooses (Helogale parvula) provide an ideal opportunity to study informative cues in acoustic communication. This study examined the information conveyed by two recruitment calls given in snake encounter and isolation contexts, and whether dwarf mongooses are able to respond differently on the basis of these cues. Vocalisations were collected opportunistically from four wild groups of dwarf mongooses. The acoustic parameters of recruitment calls were then analysed for distinction between contexts within recruitment calls in general, distinction within isolation calls between groups, sexes and individuals, and the individuality of recruitment calls in comparison to dwarf mongoose contact calls. Playback experiments were conducted to identify whether individuals were able to discriminate between snake and isolation calls, and between isolation calls of individuals from different groups. The results showed that these dwarf mongoose vocalisations convey information beyond their primary recruitment function. Recruitment calls are functionally referential, having context-specific acoustic distinctions and inciting different behavioural responses. This is in contrast to recruitment calls in banded mongooses (Mungos mungo) which differ on the basis of urgency, not context. Isolation calls specifically also inform the receiver about the identity, sex and potential group membership of the caller. The contact calls of banded mongooses and meerkats (Suricata suricatta), are also individually distinct and those of meerkats also contain group-specificity. However, banded mongooses do not discriminate between individuals and meerkats do not discriminate between groups. A prior finding showed that dwarf mongooses are able to recognise individuals based on their contact calls. The results of the current study support this as dwarf mongoose receivers are able to distinguish between isolated callers. They bias their response to isolated foreign females. Finally, the acoustic individuality of call types depends greatly on their function and the benefits of advertising identity in each context. Snake calls have a lower individual-specificity than contact calls, which in turn are less specific to caller than isolation calls. This study not only adds to the knowledge available on Herpestid communication, but also presents the first example of sex-bias in the response to mongoose vocalisations. It is also the first study in which isolation vocalisations are directly compared to other recruitment calls.

AFRIKAANSE OPSOMMING: Akoestiese kommunikasie is belangrik in sosiale vertebrate, veral diegene wat in dig-begroeide omgewings leef waar visuele seine nie goed werk nie. Geluide dra dikwels sekondêre inligting oor om vinnige en toepaslike reaksies te bewerkstellig. Hierdie funksie is noodsaaklik in langafstand kommunikasie. Die langafstand werwingsroepe van dwergmuishonde (Helogale parvula) bied ‘n ideale geleentheid om insiggewende leidrade in akoestiese kommunikasie te bestudeer. Hierdie navorsing het die inligting wat deur twee werwingsroepe (in die konteks van ontmoetings met slange of afsondering) oorgedra word, ondersoek, asook of dwergmuishonde op grond van die leidrade verskillend reageer. Roepgeluide is opportunisties van vier groepe wilde dwergmuishonde versamel. Die akoestiese parameters van werwingsroepe is vervolgens ontleed vir verskille tussen kontekste binne werwingsroepe oor die algemeen, verskille binne afsonderingsroepe ten opsigte van groep, geslag en individu, asook die individualiteit van werwingsroepe vergeleke met dwergmuishond kontakroepe. Geluidsopnames is vir dwergmuishonde teruggespeel om vas te stel of individue tussen slang- en afsonderingsroepe, en tussen afsonderingsroepe van individue van verskillende groepe kon onderskei. Die resultate toon dat dwergmuishondgeluide inligting bo en behalwe hul primêre werwingsfunksie oordra. Werwingsroepe is funksioneel verwysend, m.a.w. hulle het konteks-spesifieke akoestiese kenmerke en hulle lok verskillende gedragsreaksies uit. Dit is in teenstelling met werwingsroepe van gebande muishonde (Mungos mungo) wat ten opsigte van dringendheid, maar nie konteks nie, verskil. Spesifiek afsonderingsroepe lig die hoorder ook oor die identiteit, geslag en moontlike groepsverband van die roeper in. Gebande muishonde en meerkatte (Suricata suricatta) se kontakroepe is ook individueel verskillend en dié van meerkatte is ook groep-spesifiek. Gebande muishonde onderskei egter nie tussen individue nie, en meerkatte nie tussen groepe nie. ‘n Vorige studie het getoon dat dwergmuishonde individue op grond van hulle kontakroepe kan herken. Die resultate van die huidige studie bevestig dit, aangesien dwergmuishond hoorders tussen verskillende afgesonderde roepers kan onderskei. Hulle reageer sterker op geïsoleerde vreemde wyfies. Laastens hang die akoestiese individualiteit van roepe grootliks van hul funksie en die voordele van bekendmaking van identiteit in elke konteks af. Slangwerwingsroepe is minder spesifik aan die individu as kontakroepe, wat op hul beurt minder spesifik aan die roeper is as afsonderingsroepe. Hierdie studie brei nie net die kennis oor kommunikasie van die muishond-familie uit nie, maar beskryf ook die eerste voorbeeld van geslagsvoorkeur in die reaksie op muishondroepe. Dit is ook die eerste studie waarin afsonderingsroepe direk met ander werwingsroepe vergelyk word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100869
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