Doctoral Dissertations

Date of Award

12-1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Life Sciences

Major Professor

John L. Gittleman

Committee Members

Gary McCracken, Gordon Burghardt, Christine Boake

Abstract

A central focus of behavioral ecology is understanding the evolution and maintenance of animal societies and the cooperative interactions of individuals within these societies. The white-nosed coati Nasua narica is a sexually dimorphic carnivore with a dichotomous social structure; all adult males are solitary while all adult females live in bands. The species is therefore uniquely suited for examinations of the mechanisms underlying the maintenance of solitary and group-living societies, as well as better understanding behavioral interactions occurring within social groups. This dissertation examines the behavioral ecology and genetics of a coati population with the goals of (1) identifying ecological factors maintaining the social structure of the coati, (2) discerning patterns of relatedness, and (3) understanding the importance of kinship to an individual's receipt of the costs and benefits of living in bands. Field work took place over a five year period on Barro Colorado Island, Panama, and involved trapping, marking, habituating, and collecting detailed behavioral data on known individuals and bands. The coati was found to be almost entirely frugivorous and insectivorous; only a few plant species formed the vast majority of the coati fruit diet. When foraging on these plants, solitary males had increased foraging success relative to band members, suggesting that males were solitary not because they could not join bands but rather because they were more successful when foraging alone. Although adult females also had higher foraging success when feeding solitarily, they were unable to gain access to valuable food patches without assistance due to direct competition and aggression from larger solitary males. It is hypothesized that the coati social structure was maintained by interactions of sexual dimorphism in body size, reliance on patchy and defendable food resources, and perhaps, reproductive synchrony. Ectoparasite presence and abundance was influenced by coati social structure and by season of examination. Solitary males had increased abundances of replete and non-replete ticks relative to band members. Solitary males also scratched themselves more often and for longer periods than band members, spending approximately 6% of their activity budget on this behavior. Band members had increased likelihood of being parasitized by mites relative to solitary males. Mite prevalence within bands fluctuated temporally, with different bands independently gaining and losing mite infestations over time. Individuals within bands were homogeneous for mite presence or absence, and females who became solitary to give birth lost their mite infestations, implying mite parasitism was a cost of social contact. Multilocus DNA fingerprinting analyses revealed that coati bands were primarily extended families with occasional unrelated individuals. Unrelated individuals were found in four of six bands. Thus, despite relatively high mean relatedness, coati bands were perhaps best defined by their high variance in relatedness. Members of different bands were on average unrelated. However, occasional pairs of individuals were discernible as somewhat related, indicating gene flow among bands with no known interactions. Home ranges of bands overlapped among some but not all neighboring bands, and bands resulting fi-om known fission events retained relatively high mean relatedness for several years thereafter. Adult males inhabiting the home range of a band were generally slightly or highly related to band members. This confirmed home range analyses which found solitary males to have home ranges within or overlapping the home range of their natal bands. Genetic relatedness was important for determining whether a female gained the full benefits of living in groups. Females unrelated to other band members had increased ectoparasite loads than did females with close kin in the band. These unrelated females were also more likely to be seen solitarily than were females with close kin, and they received more aggression from band members than did the related females. Both related and unrelated individuals formed coalitions. However, related females received support more often than unrelated females. Unrelated females gave more coalition support than they received, while females with close kin in the band received support and gave support more symmetrically. Finally, unrelated females reproduced less often than females with close kin in the band.

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