T-maze behaviour in domestic chicks: a search for underlying variables

We investigated whether contrasting T-maze behaviour shown by domestic chic ks, Gallus gallus domesticus, of a broiler strain reflected underlying diff erences in their general activity levels, fearfulness or sociality. The tim e taken by 2-day-old chicks to traverse a T maze and thereby regain visual contact with their companions was measured. Chicks were categorized accordi ng to whether they completed this task quickly (HP, high performance, <25 s ) or slowly (LP, low performance, >75 s) and then housed in same-category g roups, each of eight chicks. In experiment 1, we compared the numbers of HP and LP chicks showing certain home cage behaviours (ambulation, standing, resting, maintenance, pecking, preening). No significant differences were f ound. In experiment 2, we compared the behaviour of HP and LP chicks in two tests of sociality (homecage proximity, runway) and in two tests of fear ( emergence, tonic immobility). The HP chicks stayed closer together in the h ome cage than did their LP counterparts and they spent significantly longer near a goal;box containing conspecifics in the runway than did LP ones. Co nversely, there were no significant differences between HP and LP chicks in their latency to emerge from a sheltered area into an exposed and, hence, potentially frightening one or in their tonic immobility fear reactions. Th ese findings suggest that;contrasting T-maze performance was unlikely to ha ve reflected differences in underlying activity levels or in fearfulness. C onversely, individual variation in underlying sociality was probably an inf luential variable. (C) 1999 The Association for the Study of Animal Behavio ur.