Social inhibition of territorial behaviour in yearling male collared lizards, Crotaphytus collaris

In central Oklahoma, collared lizard males display age-dependent differences in social behaviour, whereby sexually mature first-year (yearling) males adopt subordinate tactics, and males 2 years and older establish and defend all-purpose territories. We tested the hypothesis that the social activities of adult males inhibit the expression of territorial tactics in yearling males by recording the behaviour of yearlings in the presence of adult males, when all adult males were removed from study plots for 4 days, and then again when adult males were returned to their territories. The rates of yearling male patrol, display and intrasexual encounters increased during removals, especially during the last 2 days, following which the rates of these behaviour patterns declined when adult males were replaced. Yearling males also increased the frequency with which they interacted with females when adult males were removed. Moreover, the duration of intersexual encounters during the last 2 days of removal was over twice that during the first 2 days of removal, suggesting that females became more receptive to yearling males the longer adult males were absent. Our results suggest that the stable age-related behavioural differences in male collared lizards is governed by social feedback, where sexually mature yearling males are capable of displaying territorial behaviour patterns but are inhibited from doing so by the activities of adult males. (C) 1998 The Association for the Study of Animal Behaviour.