Social experience during adolescence influences how male zebra finches (Taeniopygia guttata) group with conspecifics
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Group-living animals rely on social skills which ensure beneficial interaction and prevent harmful ones with conspecifics. In a previous experiment, we demonstrated that male zebra finches reared in groups during adolescence show consistently less courtship and aggressive behaviour as adults than pair-reared males. Here we tested whether such differences affect how they group with conspecifics, as an indicator of their social integration. Zebra finches were kept in pairs (male–female or male–male) or mixed-sex groups (three males and three females) during adolescence and were introduced to an established group of unknown conspecifics during adulthood. Male courtship and aggressive behaviour were quantified directly after introduction to the group and 48 h later. At the same time, male position in relation to other birds and the number of birds in proximity were recorded. Males that grew up in a small mixed-sex group during adolescence spent more time within groups, were observed in bigger groups and lost less weight than males raised in pairs, indicating that an enriched social environment during early development may facilitate social integration. However, we observed no differences in courtship and aggressive behaviour that could predict the differences in grouping behaviour of pair- and group-reared males. We discuss alternative explanations for the difference in grouping and how to test these in future research.
KeywordsSocial competence Social integration Social experience Adolescence Phenotypic plasticity Gregariousness
We thank Ursula Kodytek, Brigitta Otte, Ursula Rennemann, Kristina Ruhe, Jana Derbogen, Stefanie Taube, Uwe Dettmer, Werner Jamin, Michael Meyerhoff and Sebastian Dietrich for taking care of the animals. We thank Suzanne von Engelhardt for polishing the language of the manuscript. This project was supported by a grant from the German Research Foundation to Hans-Joachim Bischof and Nikolaus von Engelhardt (DFG; FOR 1232: BI 245/20-1).
According to German animal protection laws, social rearing conditions and behavioural tests applied in this study are not considered experimental procedures that require specific approval by an ethical committee. Animal facilities were approved (dated 18 April 2002) for keeping and breeding zebra finches for research purposes by the local government authority responsible for health, veterinary and food monitoring (Gesundheits-, Veterinär- und Lebensmittelüberwachungsamt Stadt Bielefeld).
Zebra finches are highly social birds that roost and breed together in large colonies. The social group sizes in the present experiment are thus representative of what may occur in a natural situation. Zebra finches are generally tolerant of conspecifics and excessive and severe aggression occurs only rarely, if at all. In the present experiment, only low-intensity aggressive behaviour such as threats and chases were observed, all occurring with modest frequency. The experimental setup ensured enough space to allow birds to easily escape from any antagonistic interaction. An intervention by the experimenter to prevent physical harm to the animals was not necessary at any time. The number and distribution of food and water dispensers assured access to food and water for all birds without risk of competitive exclusion, and all experimental animals were observed to feed during the observation periods. It is thus unlikely that the observed changes in body weight are the result of an inability to reach food or water.
All birds were visually inspected on a daily basis (including weekends) by the experimenter and/or an animal caretaker. Any injuries or other health issues (recognisable by fluffed up or lethargic appearance) would have resulted in immediate removal from the experimental setting, but this was not necessary at any time.
After the experiment, stimulus birds were housed in large aviaries (3 × 3 × 3 m) separated by sex. Experimental males were individually caged and monitored for at least 1 week before being given the opportunity to breed in large outdoor aviaries. During this week, all experimental males reached their pre-experimental weight again.
Further details of breeding and housing conditions are described in the respective method sections.
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