Resource distribution mediates synchronization of physiological rhythms in locust groups

Abstract

Synchronized behaviour is common in animal groups. In ant colonies, synchronization occurs because active ants stimulate their neighbours to activity. We use oscillator theory to explain how stimulation from active neighbours synchronizes activity in groups of solitarious locusts via entrainment of internal physiological rhythms. We also show that the spatial distribution of food resources controls coupling between individual locusts and the emergence of synchronized activity. In locusts (Schistocerca gregaria), individual schedules of activity and quiescence arise from an irregular physiological oscillation in feeding excitation (i.e. hunger). We show that contact with an active neighbour increases the probability that a locust becomes active. This entrained activity decreases the time until the locust feeds, shifting the phase of its 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.

Sources of intraspecific variation in the collective tempo and synchrony of ant societies

“…Increasing values of S signify that comparatively more individuals are active together while also having more individuals inactive together. This metric, sometimes called the Fano factor in neuroscience contexts (Stevens and Zador 1998), has also been used in the past to assess variation in the synchronized motion of other insects (Despland and Simpson 2006). Repeatability estimates for each of these three waveform traits was calculated through general linear mixed-effects models, with colony ID set as a random factor and a Gaussian error distribution.…”

Plasticity of collective behavior in a nomadic early spring folivore

“…Indeed, the rhythm of alternation of collective feeding and digesting bouts accelerates at higher temperature (Peters and Despland, 2006), as interactions within a colony synchronize individual foraging schedules (Despland and Simpson, 2006). The speed at which individual caterpillars walk, eat, and digest their food depends on ambient temperature (Fitzgerald, 1995), which leads to shorter foraging and digesting bouts as temperature increases (Peters and Despland, 2006).…”

Environmental and genetic influences on the dispersal propensity of spruce budworm (Choristoneura fumiferana)

“…The frequency of dispersal in an insect population has been demonstrated to be under genetic and/or environmental control, with environmental triggers often related to conspecific density or nutrition (Harrison, ). The classic example of this phenomenon is found in the desert locust Schistocerca gregaria Forskål, where increased food availability and contact with conspecifics triggers profound behavioural and physiological changes leading to swarm formation and migration (Kennedy, ; Despland & Simpson, ; Despland & Simpson, ). Evidence for polymorphic dispersal strategies has been found frequently in the Hemiptera and Orthoptera, although they have also been identified in a wide diversity of insect taxa including Lepidoptera (Harrison, ; Zera & Denno, ).…”