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

We investigated whether contrasting T-maze behaviour shown by domestic chicks, Gallus gallus domesticus, of a broiler strain reflected underlying differences in their general activity levels, fearfulness or sociality. The time taken by 2-day-old chicks to traverse a T maze and thereby regain visual contact with their companions was measured. Chicks were categorized according 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 groups, 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 found. In experiment 2, we compared the behaviour of HP and LP chicks in two tests of sociality (home cage proximity, runway) and in two tests of fear (emergence, tonic immobility). The HP chicks stayed closer together in the home cage than did their LP counterparts and they spent significantly longer near a goal box containing conspecifics in the runway than did LP ones. Conversely, 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. These findings suggest that contrasting T-maze performance was unlikely to have reflected differences in underlying activity levels or in fearfulness. Conversely, individual variation in underlying sociality was probably an influential variable. Copyright 1999 The Association for the Study of Animal Behaviour.