Data from: Social synchronization of circadian rhythmicity in female mice depends on the number of cohabiting animals

Communal animals often engage in group activities that require temporal
synchrony among its members, including synchrony on the circadian
timescale. The principles and conditions that foster such collective
synchronization are not understood, but existing literature hints that the
number of interacting individuals may be a critical factor. We tested this
by recording individual circadian body temperature rhythms of female house
mice housed singly, in twos (pairs), or in groups of five (quintets) in
constant darkness; determining the daily phases of the circadian peak for
each animal; and then calculating the cycle-to-cycle phase relationship
between cohabiting animals over time. Significant temporal coherence was
observed in quintets: the proportion of quintets (4/7), but not pairs
(2/8), that became synchronized was greater than could be achieved by the
complete simulated reassortment of all individuals. We speculate that the
social coupling of individual circadian clocks of group members may be
adaptive under certain conditions, and we propose that optimal group sizes
in nature may depend not only on species-specific energetics, spatial
behaviour and natural history but also on the mathematics of synchronizing
assemblies of weakly coupled animal oscillators.