The multifaceted effects of starvation on arthropod behaviour

Starvation is defined as a failure to consume food following an extrinsic limitation. By focusing on arthropods, I provide here a detailed review of how starvation affects foraging behaviour, predation avoidance, aggressive interactions and reproductive behaviour. Behaviour following starvation is shaped by the trade-off between the value of food, which increases with hunger level, and other vital needs, such as reproduction and avoiding ending up as prey. Foraging should take place as long as its marginal benefit outweighs the associated costs, including the avoidance of other important activities. Because starvation affects both the benefit and cost of foraging, it has various effects on behaviour. Most of the behaviours of hungry animals are selected to increase the likelihood of detecting food and better exploit it. The effect of starvation on foraging has usually revealed an increase in activity, albeit also occasionally a decrease, possibly due to a lowered metabolic rate or exhaustion. Predation avoidance becomes compromised when arthropods are hungry. Such hunger is also expressed in choosing riskier but prey-richer habitats and in not avoiding dangerous behaviours. Starvation elevates aggression and competition, as well as cannibalism. However, starved individuals are not necessarily more often victorious in such conflicts. Reproductive activities, such as male courting, female responsiveness and mating duration, decrease under starvation. An exception to this are females that gain material benefits, such as nuptial gifts, and which often increase their sexual activity in the face of starvation. I suggest that several behavioural responses to starvation follow a hump-shaped pattern, such as an increase followed by a decrease in foraging and aggression intensities with increasing hunger level. I highlight several research approaches, such as uncovering the link between starvation-induced changes in behaviour and fitness, and their underlying physiological mechanisms.