Sex and social status affect territorial defence in a cooperatively breeding cichlid fish, Neolamprologus savoryi
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Members of social groups must defend their shared territory against both predators and competitors. However, individuals differ widely in their contributions to territorial defence. Assessing the variation in response to territorial intrusions provides insight into both the benefits and costs of group living for different group members. In this study, we assessed the response of wild Neolamprologus savoryi to experimentally staged territorial intrusions. Neolamprologus savoryi is an understudied cooperatively breeding cichlid fish endemic to Lake Tanganyika, East Africa. We found that dominant male and dominant female N. savoryi were both highly aggressive towards heterospecific predators and towards same-sex conspecific rivals. Both dominant males and females were less aggressive towards opposite-sex conspecific opponents, with the relative reduction in aggression being most pronounced in males. Subordinates provided low levels of defence against all intruder types, which suggests that subordinate N. savoryi rely on larger group members for protection. Collectively, our results provide insight into the structure and function of N. savoryi social groups, and highlights key costs and benefits of cooperation for individual social group members.
KeywordsAggression Defence Cooperation Lake Tanganyika Neolamprologus pulcher
The authors wish to thank Danny Sinyinza, Dr. Cyprian Katongo, Dr. Harris Phiri, Peter Sekazway, Clement Sichamba, Augustine Mwewa, Celestine Mwewa, Fernandez Mwewa, Gegwin Kapembwe, Damius Kapembwe, and all of the wonderful staff of the Tanganyika Science Lodge for their logistical support of the field research. The research was supported by a Natural Sciences and Engineering Research Council of Canada Discovery (NSERC) grant and equipment grant to SB, as well as Ontario Innovation Trust and Canadian Foundation for Innovation awards to SB. Further funding for the field research was provided by a Journal of Experimental Biology Travelling Fellowship to CMO, and Canadian Society of Zoologists and McMaster School of Graduate Studies research grants to ARR. CMO was supported by the E.B. Eastburn Postdoctoral Fellowship from the Hamilton Community Foundation, and is currently supported by an NSERC Postdoctoral Fellowship. ARR was supported by the Margo Wilson and Martin Daly Ontario Graduate Scholarship, and is currently supported by the Richard H. Tomlinson Postdoctoral Fellowship, and an NSERC Postdoctoral Fellowship. IYL and JKH are supported by the Department of Evolution, Ecology, and Organismal Biology at The Ohio State University, The Ohio State University Fish Systematics Endowment, and the SciFund Challenge. JKH is supported by the American Academy of Underwater Sciences. SB is supported by the Canada Research Chair Program and the NSERC Discovery Program.
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