The activity/inactivity schedules of individual animals arise from an
irregular physiological oscillation in feeding excitation (i.e. hunger).
We use oscillator theory to explain how stimulation from active neighbours
entrains these internal physiological rhythms and synchronizes activity in
groups of both gregarizing locusts and social caterpillars.
In locusts, we show that contact with an active neighbour
increases the probability of becoming active, leading to feeding and
phase-resetting of the hunger oscillation. The locusts internal
physiological rhythms are thus brought into alignment and their activity
becomes synchronized. When food resources are clumped, contact with active
locusts increases, and this increase in the strength of coupling between
individuals leads to greater synchronization of behaviour. Activity
synchronization might have functional significance in inhibiting swarming
when resources are dispersed and accelerating it in more favourable
clumped environments.
Synchronized behaviour is common in animal groups, many of them
more tightly coupled and cohesive than gregarizing locusts. In social
caterpillars for instance, colonies show a cohesive synchronized
alternation between foraging and resting bouts. We show how these
patterns of collective behaviour can emerge from interplay between
individual hunger-based activity/inactivity cycles and interactions
between colony-members.
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