Low-rank Gallus gallus domesticus chicks are better at transitive inference reasoning.

A form of deductive reasoning, transitive inference, is thought to allow animals to infer relationships between members of a social group without having to remember all the interactions that occur. Such an ability means that animals can avoid direct confrontations which could be costly. Here we show that chicks perform a transitive inference task differently according to sex and rank. In female chicks, low-ranking birds performed better than did the highest ranked. Male chicks, however, showed an inverted U-shape of ability across rank, with the middle ranked chicks best able to perform the task. These results are explained according to the roles the sexes take within the group. This research directly links the abilities of transitive inference learning and social hierarchy formation and prompts further investigation into the role of both sex and rank within the dynamics of group living.

Ecobat: An online resource to facilitate transparent, evidence-based interpretation of bat activity data.

Acoustic surveys of bats are one of the techniques most commonly used by ecological practitioners. The results are used in Ecological Impact Assessments to assess the likely impacts of future developments on species that are widely protected in law, and to monitor developments' postconstruction. However, there is no standardized methodology for analyzing or interpreting these data, which can make the assessment of the ecological value of a site very subjective. Comparisons of sites and projects are therefore difficult for ecologists and decision-makers, for example, when trying to identify the best location for a new road based on relative bat activity levels along alternative routes. Here, we present a new web-based, data-driven tool, Ecobat, which addresses the need for a more robust way of interpreting ecological data. Ecobat offers users an easy, standardized, and objective method for analyzing bat activity data. It allows ecological practitioners to compare bat activity data at regional and national scales and to generate a numerical indicator of the relative importance of a night's worth of bat activity. The tool is free and open-source; because the underlying algorithms are already developed, it could easily be expanded to new geographical regions and species. Data donation is required to ensure the robustness of the analyses; we use a positive feedback mechanism to encourage ecological practitioners to share data by providing in return high quality, contextualized data analysis, and graphical visualizations for direct use in ecological reports.

Time-dependent lateralization of social learning in the domestic chick (Gallus gallus domesticus): Effects of retention delays in the observed lateralization pattern.

Day-old chicks have been shown capable of learning to avoid pecking by observation only of a conspecific showing a disgust reaction after pecking a bitter-tasting bead. This learning is lateralized: access to the right hemisphere appears necessary for successful performance 30 min after training. This is in contrast to the non-social learning version of this learning task, in which the left hemisphere appears to play the dominant role, although both the left and right hemispheres are, in turn, subject to brief windows of "enhanced recall" during memory formation. In our present work we wished to investigate whether such recall events are also prevalent in the social learning task. We investigated 3 such windows; 25 min (a right hemisphere event), 32 min (left-hemisphere event) and 64 min (a possible left-hemisphere event following an interconnection of both hemispheres allowing memory transfer between the two hemispheres). At 32 and 64 min after training we found no evidence of functional lateralization. At 25 min, however, we found right hemisphere dominance. We suggest that a lateralization effect occurs in the social version of the PAL (passive avoidance learning) only at time points associated with right hemisphere dominance. It seems that lateralization is not able to emerge at time points where a left-hemisphere event is expected, because the two "lateralization effects" (right hemisphere dominance associated with the social task and left-hemisphere dominance associated with the PAL task) are in conflict.

Logic in an asymmetrical (social) brain: Transitive inference in the young domestic chick.

The ability of animals to perform transitive inference is associated with social group formation and dominance hierarchies. Brain lateralization is also linked to the selective pressures associated with social life. We investigated whether transitive inference is better performed by lateralized than non-lateralized brains. In the domestic chick (Gallus gallus) exposure of eggs to light before hatching leads to the development of lateralization of some visual functions. Thus, it is possible to obtain chicks with strong (light-incubated, Li-chicks) or weak (dark-incubated, Di-chicks) lateralization. Di- and Li-chicks were trained to discriminate stimulus pairs, in order to build a hierarchy (A > B > C > D > E). Chicks were subsequently tested on stimulus pairs never seen together before (AE and BD). Li-chicks performed the discrimination BD better than did Di-chicks, suggesting that exposure to light in the egg leads to an increased ability to carry out representational learning. Moreover, lateralized chicks using their left eye only (right hemisphere) during test showed a better performance than did right eye only (left hemisphere) chicks on the BD task. Females also tended to perform better than males. Results demonstrate that chicks with lateralized brain hemispheres show greater inference, and this is under right hemisphere control: the brain hemisphere that is dominant in social interactions.

Lateralization of social cognition in the domestic chicken (Gallus gallus).

In this paper, we report on the ongoing work in our laboratories on the effect of lateralization produced by light exposure in the egg on social cognition in the domestic chick (Gallus gallus). The domestic chick possesses a lateralized visual system. This has effects on the chick's perception towards and interaction with its environment. This includes its ability to live successfully within a social group. We show that there is a tendency for right brain hemisphere dominance when performing social cognitive actions. As such, chicks show a left hemispatial bias for approaching a signalled target object, tend to perceive gaze and faces of human-like masks more effectively when using their left eye, are able to inhibit a pecking response more effectively when viewing a neighbour tasting a bitter substance with their left eye, and are better able to perform a transitive inference task when exposed to light in the egg and when forced to use their left eye only compared to dark-hatched or right eye chicks. Some of these effects were sex specific, with male chicks tending to show an increased effect of lateralization on their behaviours. These data are discussed in terms of overall social cognition in group living.

Enhanced yolk testosterone influences behavioral phenotype independent of sex in Japanese quail chicks Coturnix japonica.

Studies have demonstrated an effect of yolk testosterone levels on the physiology and behavior of nestling birds. In order to investigate this phenomenon experimentally in a precocial bird, we enhanced yolk testosterone, but within the physiological range, by injecting 50 ng testosterone in ethanol into Japanese quail Coturnix japonica eggs prior to incubation. The chicks hatching from these as well as from control eggs that had received the carrier-only or were left unmanipulated were subject to a number of behavioral tests from hatching to the age of 3 weeks. In addition, fecal samples were taken during a 90-min isolation period to determine a physiological response to a stressor. Experimental chicks performed a detour task faster and approached novel objects sooner than did the controls. Chicks from treated eggs took a longer time to start distress vocalizing and also produced less distress calls during open-field trials, took on average a larger number of trials for them to show tonic immobility and also excreted lower levels of corticosterone metabolites (BM) than did the controls. In response to a stressor, excreted BM was initially higher in the control chicks, as compared to the experimental birds. Induced behavioral effects were independent of sex with no sex treatment interactions found. In sum, experimentally enhanced testosterone levels in the eggs shifted individual behavioral phenotype towards "bold" or "proactive", irrespective of sex. We conclude that testosterone in the yolk influences the coping style of hatchlings and may be a potential means of maternal influence on offspring phenotype.

Amino acid release from the intermediate medial hyperstriatum ventrale (IMHV) of day-old chicks following a one-trial passive avoidance task.

Indirect evidence has implicated glutamate and gamma-amino butyric acid in memory formation for one-trial passive avoidance learning. We have further examined this by following the time course of glutamate and gamma-amino butyric acid release from slices prepared from the intermediate medial hyperstriatum ventrale of day-old chicks (Ross 1 Chunky) trained to avoid a bead covered in the aversant methylanthranilate. At various times after training, slices of left and right intermediate medial hyperstriatum ventrale were incubated in medium containing 50 mM potassium chloride and amino acid release was determined. Thirty minutes after training there was a bilateral increase in calcium-dependent glutamate release in slices from methylanthranilate-trained chicks compared to those trained to peck water. This increase was sustained until 1 h in the left hyperstriatum when an increase in calcium-dependent gamma-amino butyric acid release was also apparent. Glutamate uptake was also enhanced in left hyperstriatum (30 and 60 min) and in the right at 30 min. In the right intermediate medial hyperstriatum ventrale of methylanthranilate birds glutamate release was increased from 3 to 6.5 h and gamma-amino butyric acid at 6.5 h: a time that corresponded to the mobilization of a late process required if long-term memory was to be formed. These results confirm that the amino acids glutamate and gamma-amino butyric acid are released from the intermediate hyperstriatum ventrale in a calcium-dependent, neurotransmitter-like manner. Furthermore, changes in the release of these two amino acids accompany memory formation for a one-trial learning task in the day-old chick.