Domestication has taken place over thousands of years and during that time we have bred animals on different traits. The red jungle fowl is the ancestor to all domesticated chicks, including the white leghorn which is used in egg production. The domestication of the red jungle fowl has resulted in behavioral changes between itself and domesticated breeds, such as white leghorn. In this study we examine how these two breeds handle stress and whether or not they use social support when coping and recovering from a stress experience. The study took place in a built arena with two stimuli animals on each side. There the animal was studied for 5 minutes, stressed for 3 minutes and studied again for 5 minutes. We found that the red jungle fowl males spent more time in the unfamiliar zone before stress than males of the white leghorn. Our results also showed that the females of white leghorn and red jungle fowl spent more time in the familiar zone than males after being stressed. This is an indication that they are more dependent on social support from familiar animals after stress than the males are. Aggressive behavior was also observed among the males. Red jungle fowl males acted aggressively towards the unfamiliar stimuli animals and the white leghorn towards the familiar stimuli animals. In conclusion, we found that the females where in greater need of social support than the males. / Biologi

The main aim of this thesis was to study domestication effects on foraging behaviour in chickens and to investigate whether and how domestication and selection for high production have influenced adaptability in chickens. Two domestic strains of chickens (egg layers and meat type chickens) and their wild ancestor, the red jungle fowl (RJF) were compared in different test situations with respect to foraging behaviour and adaptability. The domestic strains showed a modified foraging strategy, where they were less inclined to explore and feed from a hidden food source, i.e. they showed less contrafreeloading (CFL, the behaviour of working for food even though identical food can be easily obtained) than RJF. The difference in CFL between RJF and the layers were not altered by food deprivation, which suggests that the lower CFL in the layers represents a genetically based difference in feeding strategy. In addition, CFL decreased with age in RJF and layers and social isolation decreased CFL in RJF. Furthermore, when foraging, RJF acquired information about the quality of different food sources, which was utilised after a change in environmental conditions. Contrary to this, layers gained less information during foraging and showed an impaired spatial learning ability compared to RJF, and in this respect, layers showed a lower degree of adaptability. Chronic stress impaired the learning capacity of both breeds but RJF seemed to be overall faster to learn to locate food in a spatial learning task. Furthermore, stressed RJF started to eat faster in the spatial learning test than non-stressed RJF, and contrary to this, stressed layers showed a more passive response by prolonging the time to start feeding compared to non-stressed layers. This indicates a more active response to stress in RJF than in layers. Similarly, when RJF and layers were exposed to food deprivation, RJF showed an active response by increasing their time spent on foraging behaviour. The general results in this thesis most likely reflect different adaptive strategies, where RJF appear to be better adapted to a stochastic environment, and the domestic strains to grow and produce egg in a more predictable environment. The findings are in accordance with the resource allocation theory, which suggests that animals selected for high production are expected to reallocate a high proportion of resources into production traits and hence fewer resources might be left to other biological processes, e.g. exploratory behaviour. Selection for high production seems to influence the ability of chickens to cope with a changing environment, which may have implications for the welfare of chickens in a production environment.

Sexual selection acts on traits that increase the reproductive success of an individual in competition with other individuals of the same sex over reproductive opportunities, through intra-sexual competition and inter-sexual mate choice. Because males benefit more from remating than females, they are subject to more intense sexual selection. Modern genetic tools have shown that females often mate promiscuously, thus prolonging sexual selection after insemination through intra-sexual (sperm competition) and inter-sexual (cryptic female choice) episodes. Despite increasing interest in post-copulatory sexual selection, the implications of sperm competition, cryptic female choice and underpinning mechanisms remain little understood. This thesis adopts an integrated approach to quantify the relative importance of post-copulatory episodes in the operation of sexual selection, elucidate their proximate mechanisms in the red junglefowl Gallus gallus. By combining behavioural observations of replicate groups with paternity data, I show that female promiscuity decreased the total opportunity for sexual selection in a group, but accounts for an unexpectedly large proportion of the variance in male reproductive success. By comparing the operation of sexual selection on multiple male traits, I show that post-copulatory sexual selection reinforced pre-copulatory sexual selection for male social dominance and that female preferred to mate with compatible males. I used experiments to study the mechanisms of post-copulatory sexual selection by studying the effect of seminal fluid in sperm competition and cryptic female choice in relation to male status and relatedness. Following previous work indicating that seminal fluid products influence sperm quality in this species, I tested in vivo whether the seminal fluid of an ejaculate acts differentially towards sperm from the same ejaculate and rival sperm, and found no evidence for this idea. Finally, I show that cryptic female choice can drastically bias the outcome of sperm competition, and that female fowl might bias paternity toward unrelated males.