Hunger and satiety determine foraging decissions in land snails: Evidence from the invasive species Theba pisana.

• Decision-making is a characteristic of intelligence not previously observed in snails. • We demonstrate that when hungry enough snails detect and eat novel substances but reject familiar ones if sated. • This species can therefore be used as a model for studying the cognitive capacities of higher species. • The fact that snails decide whether to eat a given food or not implies that they may be misled. • This could be helpful for a more efficient deployment of baits that are currently used to protect crops. The foraging behaviour of gastropod molluscs usually involves complex decisions that provide a model for the study of high-order cognitive processes. Land snails tested for food-finding in the laboratory, however, have shown an invariable feeding pattern: novel foods are mostly missed (i.e. just found by chance) whilst familiar foods, due to a type of conditioned attraction, are always located and ingested. This effect, known as Food-attraction conditioning , has led to the conclusion that, regardless of their hunger level, land snails are both willing to eat anything at any moment and also blind to the odours of novel foods. An alternative account of these findings emerges from the fact that the snails are usually tested whilst in a moderate state of hunger, so that they benefit from feeding on known foods but not from taking the risk of feeding on those that are unknown. The present experiments suggest that it is the case. Snails of the invasive species Theba pisana were tested for food-finding according to their seasonal cycle in a laboratory located in their native Mediterranean region. Subjects collected at the beginning of their aestivation period succeed in locating novel food items after being deprived for a long period (45 days), but ignored a conditioned food when they were sated with this food at the end of their lethargy. The results allow us to conclude that the feeding behaviour of snails is the product of a complex cost-benefit analysis in which their motivational state and the stimuli they perceive (and the memory of such stimuli), are evaluated. Finally, we anticipate that these results will be of use in increasing the efficiency of current baits employed for the protection of crops. [ABSTRACT FROM AUTHOR]