Abstract: The requirement for assessing the effects of stressor combinations in improving the welfare of animals has not been widely recognised. Knowledge of the effects of concurrent stressors is needed to improve environments such as transport, where animals are presented with many simultaneous challenges. However, no method for measuring the effects of different stressors with a common unit is currently available. A locomotor passive avoidance method was developed as a common currency measure of the aversion of domestic fowl to concurrent stressors, using vibrational and thermal stressors as an exemplar. Juvenile fowl, fasted overnight, were trained to run a raceway into a goal-box for small food rewards (FR1). When running consistently, the reinforcement schedule was superimposed with a FR5 treatment schedule (60 min confinement in the goal-box with either a control of no other stressors [N] or concurrent vibration and thermal stressors [VT]). Subsequent latency to return to the goal-box was recorded as a measure of aversion. The factors affecting bird response were addressed in a series of experiments to optimise the method and clarify interpretation of results. Pre-feeding (20% ration 2 h prior to testing) did not affect response, but increasing the number of treatment presentations facilitated learning and increased method sensitivity. Treatment responses were consistent across experiments; overall VT was avoided (P<0.001), but N was not. However, there was large individual variation in response to VT. A final experiment indicated that, given a visual discriminatory cue, birds were capable of learning the required association between entering the goal-box and receiving the treatment, suggesting that the delay responses were due to aversion rather than the immediate impact of treatment on ability to respond. Further work is required to test the singular stressors, but the method retains common currency potential for assessing aversion to multiple stressors.

Abstract: This study examines the role of observation during the formation of triads in female domestic hens. Results indicate that during hierarchy formation, a hen observing agonistic interactions and conflict settlement between its former dominant and a stranger uses this information when in turn confronted by the latter. Under a first condition (E, N = 15 triads), bystanders witnessed their prior dominant being defeated by a stranger before being introduced to them. In a second condition (C1, N = 16 triads), bystanders witnessed the victory of their prior dominant over a stranger. In a third condition (C2, N = 15 triads), bystanders witnessed two strangers establishing a dominance relationship before being introduced to their prior dominant and to a stranger the former had just defeated. The behavioural strategies of bystanders depended on the issue of the conflict they had witnessed. Bystanders of the E condition behaved as having no chance of defeating the stranger. They never initiated an attack against it, and upon being attacked, readily submitted in turn to the stranger. On the contrary, bystanders of the C1 condition behaved as having some chances against the stranger. They initiated attacks in 50% of cases, and won 50% of conflicts against the stranger. Under condition C2, bystanders first initiated contact with the strangers in only 27% of cases, which approximates the average of their chances for defeating the stranger. However, bystanders finally defeated the strangers in 40% of cases. These results suggest that bystanders of conditions E and C1 gained some information on the relationship existing between their prior dominant and the stranger and that they used it coherently, perhaps through transitive inference, thus contributing to the existence of transitive relationships within the triads. Alternate explanations are examined.

Abstract: Right hemisphere advantage in individual recognition (as shown by differences between response to strangers and companions) is clear in the domestic chick. Chicks using the left eye (and so, thanks to the complete optic decussation, predominantly the right hemisphere) discriminate between stranger and companion. Chicks using the right eye discriminate less clearly or not at all. The ability of left eyed chicks to respond to differences between strangers and companions stimuli is associated with a more general ability to detect and respond to novelty: this difference between left and right eyed chicks also holds for stimuli which are not social partners. The right hemisphere also shows advantage in tasks with a spatial component (topographical learning; response to change in the spatial context of a stimulus) in the chick, as in humans. Similar specialisations of the two hemispheres are also revealed in tests which involve olfactory cues presented by social partners. The special properties of the left hemisphere are less well established in the chick. Evidence reviewed here suggests that it tends to respond to selected properties of a stimulus and to use them to assign it to a category; such assignment then allows an appropriate response. When exposed to an imprinting stimulus (visual or auditory) a chick begins by using right eye or ear (suggesting left hemisphere control), and then shifts to the left eye or ear (suggesting right hemisphere control), as exposure continues. The left hemisphere here is thus involved whilst behaviour is dominated by vigorous response to releasing stimuli presented by an object. Subsequent learning about the full detailed properties of the stimulus, which is crucial for individual recognition, may explain the shift to right hemisphere control after prolonged exposure to the social stimulus. There is a marked sex difference in choice tests: females tend to choose companions in tests where males choose strangers. It is possible that this difference is specifically caused by stronger motivation to sustain social contact in female chicks, for which there is extensive evidence. However, sex differences in response to change in familiar stimuli are also marked in tests which do not involve social partners. Finally, in both sexes there are two periods during development in which there age-dependent shifts in bias to use one or other hemisphere. These periods (days 3-5 and 8-11) coincide with two major changes in the social behaviour of chicks reared by a hen in a normal brood. It is argued that one function of these periods is to bring fully into play the hemisphere most appropriate to the type of response to, and learning about, social partners which is needed at particular points in development. Parallels are discussed between the involvement of lateralised processes in the recognition of social partners in chicks and humans.