Figure 3. Free-running periods of individual crowing rhythms are identical within groups.

(a,c) Representative actograms of crowing behavior of all individuals in one of 3 rooster groups under 12L12dimL and dimLL conditions in the presence (a) or absence (c) of the first-ranking rooster. (b,d) Periodogram analysis of crowing rhythms under the dimLL condition in the presence (b) or absence (d) of the first-ranking rooster. Free-running periods of crowing behaviors were identical within groups. However, the free-running periods were altered when the first-ranking rooster was physically removed from the group. (e) Although the first-ranking rooster always crowed first within a group, the free-running periods of crowing behavior were not always shorter in the presence of the first-ranking rooster than in its absence (mean ± SEM, n = 3 groups). Note that (a) is identical with Fig. 1A of Shimmura and Yoshimura (2013)³, because this study analyzed data from the same animals used in the previous study.