Influence of early experience on processing 2D threatening pictures by European starlings (Sturnus vulgaris).

Stimuli such as visual representations of raptors, snakes, or humans are generally assumed to be universally fear-inducing in birds and considered as a product of evolutionary perceptual bias. Both naïve and experienced birds should thus react to such stimuli with fear reactions. However, studies on different species have shown the importance of experience in the development of these fear reactions. We hypothesized that the responses of adult European starlings to fear-inducing visual stimuli may differ according to experience. We compared the reactions of Hand-raised adults with no experience of predators to those of Wild-caught adults, with potentially extensive experience with predators. Three visual stimuli (i.e. human, raptor, snake) were broadcast to 17 birds as 2D pictures (displayed via a LCD screen) with different modalities of presentation: degree of proximity and with or without movement. The results reveal that the birds were particularly sensitive to proximity and movement, with more attention towards moving stimuli and more withdrawal for close stimuli. The human stimulus elicited attention in both the distant and moving modalities but, like the other stimuli, mostly withdrawal when it was close. Developmental experience appeared to influence the emotional level, as the Hand-raised birds reacted strongly to all stimuli and all modalities, contrarily to the WC birds which performed withdrawals almost only for close stimuli and attention to moving stimuli. Stimuli proximity and movement seemed, therefore, relevant features that elicited negative reactions in Wild-caught birds. The Hand-raised birds were equally attentive to both distant and moving stimuli. Thus the young birds showed no real discrimination. Early and later experiences may, therefore, influence birds' reactions. Starlings may require experience with real threats to develop adaptive responses, i.e. limiting unnecessary loss of energy by fleeing in front of non-dangerous stimuli.

A place to hide in the home-cage decreases yolk androgen levels and offspring emotional reactivity in Japanese quail.

An animal's emotional responses are the result of its cognitive appraisal of a situation. This appraisal is notably influenced by the possibility of an individual to exert control over an aversive event. Although the fact that environment controllability decreases emotional responses in animals is well established, far less is known about its potential trans-generational effects. As the levels of avian yolk hormones can vary according to the mother's environment, we hypothesized that housing environment of mothers would modulate the quality of her eggs and in turn her offspring's behaviour. Two groups of female Japanese quail were constituted: a group that had access to a place to hide in their home-cage (Hd, n = 20) and a group that had nowhere to hide (NoHd, n = 20) when stressed. Both groups were submitted to daily human disturbances for a twenty-day-period. Hd females produced eggs with both less testosterone and androstenedione than did NoHd females. The emotional and social reactivity of Hd females' offspring were lower and their growth was slower than those of NoHd females' offspring. Our results show that a minor difference in housing environment had substantial effects on eggs and offspring. The presence of a shelter probably helped quail to cope with daily human disturbances, producing less reactive offspring. This transgenerational effect caused by an opportunity to hide could lead to applications in care of laboratory animals, conservation biology and animal welfare.

Rhythmic birds show a better social integration than arrhythmic birds.

The activity rhythms of Japanese quail vary from one individual to another. Performing a divergent selection, we obtained one line of quail expressing a robust circadian rhythmicity of feeding activity (R) and one line of quail expressing circadian arrhythmicity of feeding activity (A). We questioned whether the endogenous rhythmicity of an individual could predict its integration in a group. For that, we introduced either an R- or an A-line chick into stable groups of standard chicks. First, we evaluated proximity and synchronization of the introduced chicks on the activities of the other group members. R-chicks remained spatially and temporally closer to other group members than did A-chicks. Second, we evaluated interactions of the introduced chicks and the level of their acceptance by the other group members. R-chicks were more competent to gain access to food than were A-chicks, and separation from their group stressed R-chicks more than A-chicks. Last, successive introductions assessed age effects: before, around, and after dispersal time (∼11th day of chicks' life). Most differences between R- and A-chicks were observed between their 7th and 15th day of life. In conclusion, individual endogenous rhythms predict social integration.

Epigenetic maternal effects on endogenous rhythms in precocial birds.

Development involves interactions between genetic and environmental influences. Vertebrate mothers are generally the first individuals to encounter and interact with young animals. Thus, their role is primordial during ontogeny. The present study evaluated non-genomic effects of mothers on the development of rhythms of precocial Japanese quail (Coturnix c. japonica). First, we investigated the influence of mothering on the ontogeny of endogenous rhythms of young. We compared circadian and ultradian rhythms of feeding activity of quail reared with or without adoptive mothers. More brooded than non-brooded quail presented a circadian and/or an ultradian rhythm. Thus, the presence of the mother during the normal brooding period favors, in the long term, expression of rhythms in the young. Second, we investigated the influence of rhythmic phenotype of the mother on the development of endogenous rhythms of young by comparing quail brooded by circadian-rhythmic adoptive mothers (R) to quail brooded by circadian-arrhythmic adoptive mothers (A). More R-brooded than A-brooded quail expressed circadian rhythmicity, and circadian rhythm clarities were greater in R-brooded than A-brooded quail. Ultradian rhythmicity did not differ between R- and A-brooded quail, nor between R and A adoptive mothers. Thus, the rhythmic phenotypes of quail mothers influence the rhythmic phenotypes of their young. Our results demonstrate that mothers of precocial birds influence epigenetically the ontogeny of endogenous rhythms of the young they raise.