Abstract: Since horse breeds constitute populations submitted to variable and multiple outcrossing events, we analyzed the genetic structure and gene flows considering horses raised in France. We used genealogical data, with a reference population of 547,620 horses born in France between 2002 and 2011, grouped according to 55 breed origins. On average, individuals had 6.3 equivalent generations known. Considering different population levels, fixation index decreased from an overall species FIT of 1.37%, to an average of -0.07% when considering the 55 origins, showing that most horse breeds constitute populations without genetic structure. We illustrate the complexity of gene flows existing among horse breeds, a few populations being closed to foreign influence, most, however, being submitted to various levels of introgression. In particular, Thoroughbred and Arab breeds are largely used as introgression sources, since those two populations explain together 26% of founder origins within the overall horse population. When compared with molecular data, breeds with a small level of coancestry also showed low genetic distance; the gene pool of the breeds was probably impacted by their reproducer exchanges.

Abstract: Knowledge about social recognition and memory in animals can help us to determine appropriate management and husbandry techniques. In this study, we used a habituation–discrimination procedure to investigate the ability of horses (Equus caballus) to distinguish between the body odour samples of unfamiliar conspecifics. To pick up body odour, we rubbed material on the coat of horses and presented these unknown body odours to 16 different conspecifics of the same sex and similar age. The test consisted of two successive two-min presentations of a sample from one individual (e.g. individual ‘A’) and a simultaneous presentation of samples from individual ‘A’ and a novel individual (e.g. individual ‘B’) during a final third presentation. The results showed that horses, regardless of sex, decreased the time they spent investigating conspecific body odour across the initial two presentations—demonstrating habituation. In the final presentation, the results demonstrated successful discrimination of the previously experienced odour because horses investigated the novel olfactory sample (‘B’) significantly more than the pre-exposed sample (‘A’). Taken together, these findings suggest, for the first time, that horses are able to discriminate two stimuli derived from body odours of unfamiliar conspecifics over short period of time.

Abstract: Some researchers have proposed that natural selection has given rise in humans to one or more adaptations for altruistically punishing on behalf of other individuals who have been treated unfairly, even when the punisher has no chance of benefiting via reciprocity or benefits to kin. However, empirical support for the altruistic punishment hypothesis depends on results from experiments that are vulnerable to potentially important experimental artefacts. Here, we searched for evidence of altruistic punishment in an experiment that precluded these artefacts. In so doing, we found that victims of unfairness punished transgressors, whereas witnesses of unfairness did not. Furthermore, witnesses’ emotional reactions to unfairness were characterized by envy of the unfair individual's selfish gains rather than by moralistic anger towards the unfair behaviour. In a second experiment run independently in two separate samples, we found that previous evidence for altruistic punishment plausibly resulted from affective forecasting error—that is, limitations on humans’ abilities to accurately simulate how they would feel in hypothetical situations. Together, these findings suggest that the case for altruistic punishment in humans—a view that has gained increasing attention in the biological and social sciences—has been overstated.

Abstract: We investigated perseveration and detour behaviour in 36 equids (Equus caballus, E. asinus, E. caballus × E. asinus) and compared these data to those of a previous study on domestic dogs (Canis familiaris). The animals were required to make a detour through a gap at one end of a straight barrier in order to reach a visible target. After one, two, three or four repeats (A trials), the gap was moved to the opposite end of the barrier (B trials). We recorded initial deviations from the correct solution path and the latency to crossing the barrier. In the A trials, mules crossed the barrier significantly faster than their parental species, the horses and donkeys. In the B trials, following the change of gap location, all species showed a reduction in performance. Both dogs and horses exhibited significant spatial perseveration, going initially to the previous gap location. Donkeys and mules, however, performed at chance level. Our results suggest that hybrid vigour in mules extends to spatial abilities.

Abstract: Pair and social bonding has been documented in various taxa, where pair formations are often described as being driven by kinship or sexual motivation. However, pair-bonding between unrelated individuals where sexual motivation is not a factor is not well documented. Many social relationships and pair-bonds between members of a dyad are facilitated by each individual's ability to recognise their partner using cues which are characteristic of that particular individual. The aims of this study were i) to investigate the existence of pair-bonding in domestic donkeys and ii) to determine whether members of a dyad could recognise their companion during a Y-maze recognition test. Subjects were 55 unrelated donkeys (38 gelded males, 15 females) in seven groups of mixed or same sex, comprising 4?14 individuals. Spatial proximity (nearest-neighbour) was observed three times a day over a 22-day period. Using a simulation approach based on observed data to generate randomised nearest-neighbour matrices, the statistical significance of social relationships was estimated. Of these, 42 (79.2%) were involved in significantly (p<0.05) non-random nearest-neighbour relationships, most of which were reciprocal pair relationships. Based on the spatial data, 24 of the donkeys which had shown significant reciprocal nearest-neighbour preferences for one individual (companion) were then used in a Y-maze recognition test in which they were presented with a choice of their companion and either a familiar donkey from the same group or an unfamiliar donkey from a different group. Donkeys? spatial location in the Y-maze demonstrated a preference for their companion versus familiar (one sample Wilcoxon signed rank test, W=239, p=0.002) or unfamiliar donkeys (W=222, p=0.041). These results verify anecdotal evidence from donkey handlers that donkeys often form pair-bonds, and show that reciprocal social preference and recognition are the basis of these. Pair-bond formation and companionship among donkeys have potential implications for their management, husbandry and welfare.