Time filter

Source Type

Altenberg bei Linz, Austria

The focus of the present study was a release project on jackdaws (Corvus monedula) which was carried out in two steps in 2007 and 2009. In 2007 we focused on the spatial dispersion of individuals which started gradually but then turned into a stepwise increase. A change in the functional use of space was associated with the birds' spatial dispersion into areas other than those immediately surrounding the aviary in which especially the centre of the birds' activities was relocated. 2009 focused on the analysis of the process how a newly released group of jackdaws and the already existing wild colony of birds would unite into a single social group. In this process both colonies used different strategies: in contrast to the individuals of the wild colony that mainly approached the newly released individuals in an aggressive manner, the latter initiated more sociopositive interactions towards the former. Although after two weeks the two colonies could be considered as one when referring to their spatial cohesiveness, our results show that their social cohesiveness was achieved only after about two months. Furthermore, our study indicates which factors of the context and the biology of jackdaws, respectively, may be especially important for a successful release in these birds: visual acquaintance with the new environment, social dynamics of jackdaw colonies that represent free entry groups in which emigration and immigration are frequent phenomena and can be used for releasing purposes, and the importance of an established dominance hierarchy due to which dominant individuals can take the lead while subdominant conspecifics may follow them. © DO-G, IfV, MPG 2011.

Rosas A.,KLI for Evolution and Cognition Research | Rosas A.,National University of Colombia
Journal of Theoretical Biology | Year: 2010

Evolutionary game theory has shown that human cooperation thrives in different types of social interactions with a PD structure. Models treat the cooperative strategies within the different frameworks as discrete entities and sometimes even as contenders. Whereas strong reciprocity was acclaimed as superior to classic reciprocity for its ability to defeat defectors in public goods games, recent experiments and simulations show that costly punishment fails to promote cooperation in the IR and DR games, where classic reciprocity succeeds. My aim is to show that cooperative strategies across frameworks are capable of a unified treatment, for they are governed by a common underlying rule or norm. An analysis of the reputation and action rules that govern some representative cooperative strategies both in models and in economic experiments confirms that the different frameworks share a conditional action rule and several reputation rules. The common conditional rule contains an option between costly punishment and withholding benefits that provides alternative enforcement methods against defectors. Depending on the framework, individuals can switch to the appropriate strategy and method of enforcement. The stability of human cooperation looks more promising if one mechanism controls successful strategies across frameworks. © 2010.

Schwab C.,KLI for Evolution and Cognition Research
PloS one | Year: 2012

Other-regarding preferences are a critical feature of human cooperation but to what extent non-human animals exhibit these preferences is a matter of intense discussion. We tested whether jackdaws show prosocial behaviour (providing benefits to others at no cost to themselves) and altruism (providing benefits to others while incurring costs) with both sibling and non-sibling recipients. In the prosocial condition, a box was baited on both the actor's and the recipient's side (1/1 option), whereas another box provided food only for the actor (1/0 option). In the altruistic condition, the boxes contained food for either the actor (1/0 option) or the recipient (0/1 option). The proportion of selfish (1/0 option) and cooperative (1/1 and 0/1 option, respectively) actors' choices was significantly affected by the recipients' behaviour. If recipients approached the boxes first and positioned themselves next to the box baited on their side, trying to access the food reward (recipient-first trials), actors were significantly more cooperative than when the actors approached the boxes first and made their choice prior to the recipients' arrival (actor-first trials). Further, in recipient-first trials actors were more cooperative towards recipients of the opposite sex, an effect that was even more pronounced in the altruistic condition. Hence, at no cost to the actors, all recipients could significantly influence the actors' behaviour, whereas at high costs this could be achieved even more so by recipients of different sex. Local/stimulus enhancement is discussed as the most likely cognitive mechanism to account for these effects.

Voelkl B.,Humboldt University of Berlin | Voelkl B.,Center for Integrative Life science | Kasper C.,University of Strasbourg | Schwab C.,KLI for Evolution and Cognition Research
American Journal of Primatology | Year: 2011

Social network analysis (SNA) is a general heading for a collection of statistical tools that aim to describe social interactions and social structure by representing individuals and their interactions as graph objects. It was originally developed for the social sciences, but more recently it was also adopted by behavioral ecologists. However, although SNA offers a full range of exciting possibilities for the study of animal societies, some authors have raised concerns about the correct application and interpretation of network measures. In this article, we investigate how reliable and how stable network measures are (i.e. how much variation they show under re-sampling and how much they are influenced by erroneous observations). For this purpose, we took a data set of 44 nonhuman primate grooming networks and studied the effects of re-sampling at lower re-sampling rates than the originally observed ones and the inclusion of two types of errors, "mis-identification" and "mis-classification," on six different network metrics, i.e. density, degree variance, vertex strength variance, edge weight disparity, clustering coefficient, and closeness centrality. Although some measures were tolerant toward reduced sample sizes, others were sensitive and even slightly reduced samples could yield drastically different results. How strongly a metric is affected seems to depend on both the sample size and the structure of the specific network. The same general effects were found for the inclusion of sampling errors. We, therefore, emphasize the importance of calculating valid confidence intervals for network measures and, finally, we suggest a rough research plan for network studies. © 2011 Wiley-Liss, Inc.

Discover hidden collaborations