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Fear is a concept comprising several dimensions, but the nature of these dimensions and the relationships between them remain elusive. To investigate these dimensions in birds, we have used two genetic lines of quail divergently selected on tonic immobility duration, a behavioural index of fear. These two lines differ in their behavioural response to some, but not all, fear-inducing situations. In the present study, we investigated the contribution of human intervention in the differentiation between the two lines. To do this, fear responses towards a novel object were compared between lines in three conditions: (1) in the home cage without any human intervention, (2) in the home cage after human handling and (3) after placement in a novel environment by human handling. Fear behaviour differed between lines after human handling, with or without placement in a novel environment, but presentation of a novel object in the home cage without any human intervention induced similar fear responses in the two lines of quail. These results lead us to suggest that in quail, human intervention evokes a dimension of fear that differs from that evoked by sudden presentation of a novel object, in that these two dimensions may be selected independently., (Copyright 2010 Elsevier B.V. All rights reserved.)

Most tests used to study fear in birds involve transferring them to a novel environment, which constitutes a bias in studies aiming at identifying the neural correlates of a specific fear-inducing situation. In order to investigate fear in birds with minimum interference by humans, behavioural and endocrine responses to the presentation of a novel object in the home cage were investigated in two lines of Japanese quail divergently selected for long or short duration of tonic immobility, a behavioural index of fear. Presentation of the novel object induced typical fear responses (avoidance of the object, increased pacing and increased plasma corticosterone levels) that were similar in the two lines of quail. Presentation of a novel object in the home cage thus appears to be a suitable stimulus to induce fear reactions in quail, with minimum interference from other motivational systems. The fact that quail of both lines reacted similarly in this test, while they are known to differ greatly in their behavioural responses to other fear-inducing tests, illustrates the multidimensional nature of fear.

Sheep are able to discriminate photographs of conspecific faces. The present study investigates adult ewe's recognition of faces of the same animal between different ages or between different orientations. Twelve adult sheep were first trained to discriminate between faces of two unfamiliar animals, one of which was associated with a food reward. Transfer of discrimination from this pair to the same pair but at a different age, or in a different orientation, was then evaluated (transfer test), and compared with a new pair of the same condition (control test). Learned discrimination of a frontal view of unfamiliar 3-month-old lambs' faces improved subsequent discrimination of the same pair when they were 1-month-old in comparison to discrimination of new 1-month-old faces. Moreover, sheep that were trained to discriminate frontal views of unfamiliar adult individuals discriminated profile views of the same animals more accurately than that of novels. However, learned discrimination of the profile view of unfamiliar adult faces had no effect on subsequent discrimination of the frontal view of that same pair. These results suggest that to some extent sheep recognise faces of unfamiliar animals at different ages and in different orientations.