Subordinate removal affects parental investment, but not offspring survival in a cooperative cichlid

Bruintjes, Rick; Heg-Bachar, Zina; Heg, Dik (2013). Subordinate removal affects parental investment, but not offspring survival in a cooperative cichlid. Functional Ecology, 27(3), pp. 730-738. Blackwell Scientific Publications 10.1111/1365-2435.12088

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Summary Subordinates in cooperative breeding systems may provide help to dominant pairs, who can benefit by either an increased total investment in their current brood or a reduced personal contribution to this investment. In the social cichlid Julidochromis ornatus, one large male subordinate generally spends 90% of his time in close proximity to the breeding shelter, whereas the dominants only spend 50% of their time close to the shelter. We experimentally removed the large subordinate for 30 days (approximating one breeding cycle) to study the investment strategies of dominants and the effects on offspring survival, while accounting for subordinate immigration. Experimental groups were compared with control groups, from which subordinates were also caught but not removed. On day one following removal, we tested whether dominants overcompensated, fully compensated or undercompensated for absence of the subordinate on several parental behaviours. Moreover, we tested whether the pairs' potential compensatory behaviour remained high seven days following large subordinate removal. One day following removal, dominants increased their time spent in the territory and their frequency of breeding shelter visits and defence, compared with the pre-removal phase and control groups. The dominant pair overcompensated for the loss of subordinate help in their breeding shelter visits, fully compensated in defence and undercompensated their time spent in the territory. Seven days after large subordinate removal, behavioural differences between treatments had disappeared. However, when distinguishing between groups with or without a new immigrant subordinate, dominant pairs only diminished investment in the presence of an immigrant, suggesting a compensatory role of the large subordinate. Finally, survival of juvenile group members was not affected by the treatment. Our experiments indicate that the presence of a large subordinate does not increase the dominant pairs' current reproductive success, but instead allows them to reduce their personal contribution to investment in the current brood. In addition, we illustrate that dominants may show strikingly different compensatory responses depending on the type of behaviour and emphasize the importance of immigrant subordinates to relieve dominants from costly compensatory responses in cooperative breeding systems.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Pre-clinic Human Medicine > CTU Bern
08 Faculty of Science > Department of Biology > Institute of Ecology and Evolution (IEE)
04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine

UniBE Contributor:

Bruintjes, Derk Frederik; Heg-Bachar, Zina and Heg, Dierik Hans

Subjects:

500 Science > 570 Life sciences; biology
600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services

ISSN:

0269-8463

Publisher:

Blackwell Scientific Publications

Language:

English

Submitter:

Doris Kopp Heim

Date Deposited:

08 Feb 2014 09:35

Last Modified:

14 Jul 2015 08:02

Publisher DOI:

10.1111/1365-2435.12088

Uncontrolled Keywords:

cichlidae, compensation, cooperative breeding, helping behaviour, investment, Lake Tanganyika, load-lightening, offspring survival

BORIS DOI:

10.7892/boris.41070

URI:

https://boris.unibe.ch/id/eprint/41070

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