Extra food provisioning does not affect behavioral lateralization in nestling lesser kestrels

Costs and benefits of brain lateralization may depend on environmental conditions.Growing evidence indicates that the development of brain functional asymmetries is adaptively shaped by the environmental conditions experienced during early life.Food availability early in life could act as a proxy of the environmental conditions encountered during adulthood,but its potential modulatory effect on lateralization has received little attention.We increased food supply from egg laying to early nestling rearing in a wild population of lesser kestrels Falco naumanni,a sexually dimorphic raptor,and quantified the lateralization of preening behavior(head turning direction).As more lateralized individuals may perform better in highly competitive contexts,we expected that extra food provisioning,by reducing the level of intra-brood competition for food,would reduce the strength of lateralization.We found that extra food provisioning improved nestling growth,but it did not significantly affect the strength or direction of nestling lateralization.In addition,maternal body condition did not explain variation in nestling lateralization.Independently of extra food provisioning,the direction of lateralization differed between the sexes,with female nestlings turning more often toward their right.Our findings indicate that early food availability does not modulate behavioral lateralization in a motor task,suggesting limited phenotypic plasticity in this trait.

Male and female guppies differ in problem-solving abilities

In a number of species,males and females have different ecological roles and therefore might be required to solve different problems.Studies on humans have suggested that the 2 sexes often show different efficiencies in problem solving tasks;similarly,evidence of sex differences has been found in 2 other mammalian species.Here,we assessed whether a teleost fish species,the guppy.Poecilia reticulata,displays sex differences in the ability to solve problems.In Experiment 1,guppies had to learn to dislodge a disc that occluded a feeder from which they had been previously accustomed to feed.In Experiment 2,guppies had to solve a version of the detour task that required them to learn to enter a transparent cylinder from the open sides to reach a food reward previously freely available.We found evidence of sex differences in both problem-solvingi tasks.In Experiment 1,females clearly outperformed males,and in Experiment 2,guppies showed a reversed but smaller sex difference.This study indicates that sex differences may play an important role in fish's problem-solving similar to what has previously been observed in some mammalian species.

Vegetation cover induces developmental plasticity of lateralization in tadpoles

Lateralization of cognitive functions influences a large number of fitness-related behaviors and shows,in most species,substantial variation in strength and direction.Laboratory works and field data have suggested that this variation is often due to adaptive phenotypic plasticity.Strong lateralization should be favored in some ecological conditions,for example,under high risk of predation.For anuran tadpoles,the presence of cover affects predation risk,with tadpoles being more exposed to predators in environments with reduced cover.We tested the hypothesis that the amount of cover experienced early in life affects lateralization in the edible frog,Pelophylax escu-lentus,tadpoles.We exposed embryos and larvae to high or low vegetation cover environments.For half of the subjects,the treatment was constant whereas the remaining subjects were switched to the opposite treatment after hatching.In agreement with the theoretical expectation,tadpoles exposed to low vegetation cover for the entire development were more lateralized and showed a stronger alignment in directionality of lateralization compared with tadpoles exposed to high vege-tation cover.This indicates a possible role of natural variation in vegetation abundance and deve卜opmental plasticity as determinants of between-population and between-individual differences in lateralization.We also found that shifting from high to low vegetation cover treatments and vice versa disrupted lateralization alignment,suggesting that developmental trajectories for this trait are determined at the embryonic stage and need environmental stability to be fully expressed.