Camiones autónomos

The overall aims of the research described in this dissertation were to determine the effects of corticosterone on fear behaviour, reproductive function, and plasma

corticosterone responses to stressors in Japanese quail, both during and after treatment, and to examine if plasma corticosterone responses to similar emotional stressors, and to different types of emotional and physical stressors are related in individual quail. Transient, or acute, increases in plasma corticosterone concentrations for minutes to hours are thought to be beneficial in animals, whereas sustained, or chronic, elevations in plasma corticosterone for days or weeks can have detrimental effects (Breuner et al., 2008). Although the potentially deleterious effects of elevated plasma corticosterone concentrations in birds are well known, there is no knowledge of how birds might recover from chronically elevated plasma corticosterone concentrations. Plasma

corticosterone increases when birds experience stressors, and many of the stressors birds will experience in the foreseeable future will be anthropogenic in origin. A combination of climate change and human disturbance, otherwise known as global change, could lead to chronic stress in individuals of many species of birds with devastating

consequences (Wingfield, 2008). Stress responses and fear behaviour can help birds to cope in changing environments, and knowledge of how elevated plasma corticosterone might affect responses to stressors and fear behaviour is crucial to understand how birds might be affected by global change. Research on avian personalities has explored the relationship between hypothalamo-pituitary-adrenal (HPA) axis activity and fearfulness in quail that have been artificially selected on plasma corticosterone responses to emotional stressors. It is proposed that quail of a low stress line with lower

corticosterone responses and lower levels of fearfulness have proactive personalities, whilst quail of a high stress line with higher corticosterone responses and higher levels of fearfulness have reactive personalities (Cockrem, 2007). It is unknown, however, if quail from unselected populations also show consistent levels of fearfulness in a range of behaviour tests, or if HPA axis activity and fearfulness are related in unselected quail.

Of all the studies of plasma corticosterone responses to stressors in birds the proportion that measured responses of individuals to two or more stressors, or to physical stressors, is strikingly low. Indeed, the great majority of studies have measured corticosterone responses of birds to standardised artificial emotional stressors on just one occasion. A major assumption of avian stress endocrinology is that corticosterone responses to standardised emotional stressors reflect the responsiveness of the HPA axis of birds to stressors in general (Breuner et al., 2008), but there are no data to confirm this

assumption. Furthermore, whilst there are marked individual differences between birds in their corticosterone responses to a single stressor, it is unknown if measuring the responsiveness of the HPA axis of birds on a single occasion truly reflects the

phenotype of the sampled individuals. Studies of plasma corticosterone responses of birds to two or more stressors are clearly required to determine if consistent individual differences exist in the corticosterone responses of birds to different types of stressors. The main questions addressed in the present study of Japanese quail were:

1. Is corticosterone responsible for stressor-induced increases in fear behaviour in quail?

2. Do individuals from a population of quail not artificially selected on low or high plasma corticosterone responses to an emotional stressor show consistently low or high levels of fearfulness in a range of behaviour tests?

3. Is reproductive function and body weight in quail permanently affected by chronic corticosterone treatment?

4. Do elevated plasma corticosterone concentrations alter corticosterone responses of quail to a subsequent fasting stressor?

5. Are plasma corticosterone responses to similar emotional stressors related in individual quail?

6. Can treatment with insulin or lipopolysaccharide be physical stressors in quail? 7. Do plasma corticosterone responses to an artificial emotional stressor reflect the

responsiveness of the HPA axis of quail to physical stressors, and hence, to stressors in general?

8. Are magnitudes of plasma corticosterone responses to an emotional stressor related to levels of fearfulness in individuals from a population of quail not artificially selected on low or high plasma corticosterone responses to an emotional stressor?

Chapter’s two to four present results from an experiment in which behavioural and physiological data were collected from groups of laying quail treated with

corticosterone in their drinking water for 21 days. Chapter two describes relationships between corticosterone and behaviour in quail, presents results on the consistency of responses of quail in behaviour tests of fear, and addresses questions one and two. Chapter three describes plasma corticosterone profiles in control and treated birds and the effects of corticosterone in laying quail both during and after treatment, and

addresses question three. Control and treated quail were subjected to 24 h of fasting to investigate the effects of elevated plasma corticosterone concentrations on

corticosterone responses to a potential stressor. This study addresses question four and the results are presented in Chapter four.

Chapter’s five to seven describe experiments in which plasma corticosterone responses to different stressors were characterised in adult quail. Corticosterone responses of quail to 15, 30 and 60 min handling followed by confinement for 45, 30 or 0 min respectively were measured to address question five and this study is described in Chapter five. Responses of quail to treatment with insulin or treatment with

lipopolysaccharide (LPS) were measured to investigate if these treatments could be physical stressors in quail. This study addresses question six and the results are

presented in Chapter six. Questions seven and eight were addressed in Chapter seven. Corticosterone responses of individual quail to emotional (handling) and physical (treatment with insulin or treatment with LPS) stressors were characterised to determine if responses of birds to the two classes of stressor are related, and behavioural responses in novel object tests of fear behaviour were examined for comparison with plasma corticosterone responses to handling and confinement in individual quail.

2. Relationships between corticosterone and