Play and social relationships in the meerkat (Suricata suricatta)

Sharpe, Lynda L. (2005-04)

Thesis (PhD)--Stellenbosch University, 2005.

Thesis

ENGLISH ABSTRACT: Despite more than three decades of research, and the postulation of more than 30 hypotheses of function, the adaptive significance of play remains unknown. This study quantitatively evaluated a selection of hypotheses of function, using data collected from a wild population of small, social carnivore, the meerkat, Suricata suricatta. The study found that although play in meerkats carried an energetic cost, with individuals modulating their frequency of play in response to their energy intake, none of the hypotheses evaluated by the study could identify the adaptive benefits that meerkats derived from play. Play did not increase 'social harmony' by reducing aggression between playmates, nor did it strengthen an individual's bonds to its social group, such that it remained in the group for longer, or contributed more to the group's cooperative activities. There was no evidence that meerkats used play to strengthen alliances between individuals, and young meerkats played no more frequently with their future dispersal partners than with matched controls with which they did not disperse. Play fighting experience did not improve a meerkat's subsequent fighting skills, and individuals that ultimately won the dominant breeding position within a group (through serious fighting) played no more frequently, and no more successfully, as youngsters, than the littermates that they defeated in combat. Although play was inhibited by aggression, meerkats did not use play to contest, assert or establish dominance status, and there was little evidence to suggest that the preference young meerkats showed for play partners that were well matched in age, size and ability arose from their use of play for self-assessment. This study assessed only those hypotheses of function that predicted benefits that were of importance to the inclusive fitness of the study species. For example, the enhancement of social harmony and group cohesion should be invaluable to a species whose survival is dependent upon social cooperation; and the high reproductive skew exhibited by this species places huge value upon fighting skill and the ability to win social dominance. As a consequence, this study's negative findings suggest strongly that play is not capable of providing these benefits, and that play behaviour is unlikely to be used for these purposes in any mammal species. I conclude that the most likely function of play (based on play's ubiquitous characteristics, and the findings of neurological research on rats) is the promotion of growth of the cerebral cortex.

AFRIKAANSE OPSOMMING: Ten spyte van meer as drie dekades van navorsing en die voorstelling van meer as 30 hipoteses oor funksie, bly die aanpassingswaarde van spelonbekend. Hierdie studie is 'n kwantitatiewe evaluasie van verskeie hipoteses oor funksie, en gebruik data versamel vanuit 'n wilde bevolking van 'n klein sosiale karnivoor, die meerkat, Suricata suricatta. Die studie het bevind dat hoewel spel in meerkaaie 'n energetiese koste beloop, met individue wat hul spelfrekwensie aanpas by energie-inname, geen-een van die hipoteses onder beskouing die aanpassingswaarde van spel vir meerkaaie kon verduidelik nie. Spel het nie "sosiale harmonie" bevorder deur die afuame in aggressie tussen speelmaats nie, en het ook nie 'n individu se verbintenis tot sy sosiale groep versterk sodat hy langer in die groep sou bly of meer sou bydra tot samewerkingsaktiwiteite nie. Daar was geen bewyse vir die gebruik van spel in die versterking van bondgenootskappe tussen individue nie, en jong meerkaaie het nie meer gereeld met toekomstige verspreidings-venote gespeel as met gepaarde kontroles saam met wie hulle nie uiteengegaan het nie. Speelse gevegte het nie 'n meerkat se daaropvolgende gevegsvermoëns verbeter nie, en die individue wat uiteindelik die dominante voortplantingsposisie in 'n groep gewen het (deur ernstige stryd) het nie meer gereeld ofmeer suksesvol as jongelinge gespeel in vergelyking met die werpselmaats wat hulle in die stryd oorwin het nie. Hoewel spel deur aggressie onderdruk is, het meerkaaie spel nie gebruik om dominante range te beveg, bevestig of tot stand te bring nie. Daar was min bewyse ter ondersteuning van die voorstel dat jong meerkaaie se voorkeur vir speelmaats wat hul gelyke is in ouderdom, grootte en vermoë, onstaan het in die gebruik van spel vir selfondersoek. Hierdie studie het slegs die hipoteses van funksie beskou wat voorspellings gemaak het oor die voordele wat belangrik is in die inklusiewe fiksheid van die studie-species. Byvoorbeeld, die verbetering van sosiale harmonie en groepsamehang behoort van onskatbare waarde te wees vir 'n species wat afhanklik is van sosiale samewerking vir oorlewing; en die hoë graad van voorkeuraanwas duidelik in hierdie species plaas groot waarde op gevegsvaardighede en die vermoë om sosiale dominansie te wen. Gevolglik dui hierdie ondersoek se negatiewe bevindinge daarop dat spel nie hierdie voordele kan bied nie, en dat speelgedrag heel waarskynlik nie vir hierdie doeleindes in enige soogdier-species gebruik word nie. Ek kom tot die gevolgtrekking dat die heel waarskynlikste funksie van spel (gebaseer op spel se alomteenwoordige kenmerke en die bevindinge van neurologiese navorsing op rotte) die bevordering van groei in die serebrale korteks is.

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