Group structure in a restricted entry system is mediated by both resident and joiner preferences
- 234 Downloads
The benefits of grouping behaviour may not be equally distributed across all individuals within a group, leading to conflict over group membership among established group members, and between residents and outsiders attempting to join a group. Although the interaction between the preferences of joining individuals and existing group members may exert considerable pressure on group structure, empirical work on group living to date has focussed on free entry groups, in which all individuals are permitted entry. Using the humbug damselfish, Dascyllus aruanus, we examined a restricted entry grouping system, in which group residents control membership by aggressively rejecting potential new members. We found that the preferences shown by joining members were not always aligned with strategies that incurred the least harm from resident group members, suggesting a conflict between the preferences of residents and preferences of group joiners. Solitary fish preferred to join familiar groups and groups of size-matched residents. Residents were less aggressive towards familiar group joiners. However, resident aggression towards unfamiliar individuals depended on the size of the joining individual, the size of the resident and the composition of the group. These results demonstrate that animal group structure is mediated by both the preferences of joining individuals and the preferences of residents.
KeywordsGroup living Social organisation Dascyllus aruanus Membership preferences
We wish to thank Prof. David Booth for advice on the biology and behaviour of Dascyllus spp., and Kylie, Dave, Russ and Jen at One Tree Island Research Station for their assistance in the field. We also thank two anonymous reviewers for comments that greatly improved the manuscript. LAJ, JEHR, CA, DIR and AJWW were supported by funds supplied by University of Sydney. DIR was also supported by the Class of 1877 Research Fund. Australian ethics approval for this study was granted by the University of Sydney’s Animal Ethics Committee (L04/9-2008/1/4877). After experiments were completed, fishes were returned to where they were caught. Fishes were kept in captivity for a maximum of 4 days.
Conflict of interest
The authors declare that they have no conflict of interest.
- Asoh K (2003) Gonadal development and infrequent sex change in a population of the humbug damselfish, Dascyllus aruanus in continuous coral-cover habitat. Mar Biol 142:1207–1218Google Scholar
- Booth DJ, Wellington G (1995) Settlement preferences in coral-reef fishes: effects on patterns of adult and juvenile distributions, individual fitness and population structure. In: Joint United-States/Australia Workshop on Recruitment and Population Dynamics of Coral-Reef Fishes (Reefish 95), Kuranda, Australia, pp 274–279Google Scholar
- Dugatkin LA, Sih A (1998) Evolutionary ecology of partner choice. In: Dukas R (ed) Cognitive ecology. University of Chicago Press, Chicago, pp 379–403Google Scholar
- Krause J, Ruxton GD (2002) Living in groups. Oxford university Press, New YorkGoogle Scholar
- Pulliam HR, Caraco T (1984) Living in groups: is there an optimal group size? In: Krebs CJ, Davies NB (eds) Behavioural ecology: an evolutionary approach, 2nd edn. Sinauer Associates, Sunderland, pp 122–147Google Scholar
- Ward AJW, Hart PJB (2003) The effects of kin and familiarity on interactions between fish. Fish Fish 4:348–358Google Scholar
- Willmer PG (1985) Thermal ecology, size effects, and the origins of communal behaviour in Cerceris Wasps. Behav Ecol Sociobiol 17:151–160Google Scholar
- Wilson EO (1975) Sociobiology: the new synthesis. Harvard University Press, CambridgeGoogle Scholar