The behavioural ecology and endocrinology of cooperative breeding in the cichlid, Neolamprologus pulcher

Cooperation and conflict in social groups have been studied for decades using an ultimate or a functional approach. To date, few studies have attempted to clarify the costs and benefits of cooperation and conflict from a proximate perspective. Proximate mechanisms are interesting because they shed light on functional explanations for adaptations. For my doctoral research I have used an integrative approach to the study of cooperation and conflict in wild social groups by examining how ecology and hormones interact to influence behaviour.;Using this combination approach of laboratory and field work, I showed that, in N. pulcher, guarding of the young and territory defence is enhanced by androgens. Females provided more care than males and also had higher levels of testosterone. These results are in contrast to many previous results from the avian literature. Unlike birds, in fish the typical form of parental care is guarding of young. Using a laboratory manipulation experiment, I further confirmed that females not only had higher testosterone than males but also showed more dramatic increases in two androgens (testosterone and 11-ketotestosterone: a prime fish androgen) as a result of an aggressive interaction. These results provided the first account of support for the challenge hypothesis in males and females of the same species. My third major study was focused on understanding the tradeoff experienced by females when mated with a male who already has another female partner. I found that monogamous females enjoyed more care from their partner compared to polygynous females. Interestingly, there was no difference in the survival of young between monogamous and polygynous groups. These results suggest that female N. pulcher breeders may be gaining good genes for their sons and daughters by mating with a polygynous male because these males were shown to be larger and presumably of better quality. Finally, in my fourth study, I manipulated the level of threat to various wild groups of fish to tease apart how social status and sex influence defence priorities. Female breeders and helpers defended the territory and the young from all the intruder types while male breeders only defended when their lives or their breeding positions were challenged. These results suggest that females and helpers prioritize current over future reproduction while males prioritize their future reproductive success.;In combination, these four studies made use of multi-level analyses combining behavioural observations in conjunction with the quantification of hormones, to better clarify the proximate as well as ultimate causes for cooperation and conflict. I have been the first to establish baseline androgen levels in female cooperatively breeding fish (both breeders and helpers). My doctoral research has set the foundation for hormone analyses in cooperatively breeding fish and more specifically in the cichlid, N. pulcher.;My doctoral research made use of the cooperatively breeding fish, Neolamprologus pulcher, as a model system with which to study cooperative behaviour and natural selection. Endemic to Lake Tanganyika in the African rift valley, N. pulcher lives in semi-permanent social groups consisting of a breeding pair and one to twenty subordinate helpers. N. pulcher has a mixed mating system in the field; female breeders and their helpers can be associated with a monogamous male (one who participates in parental care in only one group) or can be part of a harem belonging to a polygynous male (one that participates in care in two or more groups). Each female and her helpers remain on a single territory, but males can hold multiple territories (each with its own female and helpers). N. pulcher provides an excellent model species to study sex and status differences in care behaviour because parents and helpers of both sexes remain on the territory and actively participate in the rearing of young and do so year round. Additionally, the species is convenient and easy to manipulate both in the laboratory and in the field setting and allowed me the opportunity to conduct ecologically relevant field studies and experiments and combine these with controlled laboratory experiments.