THE SOCIAL FACILITATION OF DRINKING - WHAT IS FACILITATED, AND WHO ISAFFECTED

The effect of a drinking companion on conspecifics was investigated us ing domestic hens (Gallus gallus domesticus). The two aims of the inve stigation were firstly to see whether drinking is sensitive to social facilitation, and if so, to see whether it follows the same pattern as that of feeding, i.e. whether it acts primarily on the drinking behav iour rather than the amount ingested. The second aim was to see whethe r differences in how influenced the birds were by a drinking companion correlated with one or more social or non-social trails. Social facil itation was measured by comparing the intake and number of 'head-ups' (i.e. swallowing) of an individual in the presence of a thirsty or non -thirsty companion. The traits measured were as follows: the rank with in each pair, social dependence/fear, reaction to a novel object, reac tion in a feeding-inhibition test, and finally weight (as a possible i ndex of the overall rank of the birds in the group). Social facilitati on of drinking occurs bur acts primarily on drinking behaviour (number of 'head ups'); birds do not swallow as much per 'head up' as when th ey themselves are thirsty. The lightest (possibly most subdominant) bi rds were also the ones most influenced by the drinking conspecific. Fu rthermore, the heaviest (possibly most dominant) individuals were the ones with the shortest social distance and the longest latency in appr oaching a novel object. This meant that the birds that were most influ enced by a drinking companion were also the individuals that were leas t fearful and showed the highest degree of exploration.