Abstract: Gestures and facial displays are involved in regulating many aspects of mammal social life such as aggression, dominance-subordinate relationships, appeasement and play. Playful activity is an interesting behaviour for examining the role of signals as intentional communication systems. When animals play they perform patterns that are used in other serious contexts. To avoid miscommunication, many species have evolved signals to maintain a playful mood. Bonobos, Pan paniscus, with their flexible social relationships and playful propensity, may represent a good model species to test some hypotheses on adult play signalling. I analysed the potential roles of facial play expressions and solitary play in soliciting and regulating social play and found that adult bonobos used the play face (relaxed open-mouth display) in a selective manner. Play faces were more frequent during social than solitary play and, within social play, polyadic sessions (even though less frequent than dyadic sessions) were characterized by a higher frequency of signals. Following the rule of play intensity matching, play faces were more frequent when the two players matched in age and size (sessions among adults). Moreover, among dyads there was a positive correlation between the frequency of aggressive interactions performed and the frequency of play signals used, thus suggesting that signals are crucial in play negotiations among individuals showing high baseline levels of aggression. Finally, solitary play, especially when it involved pirouettes and somersaults, had an important role in triggering social play.

Abstract: This study examined characteristics of visual recognition of familiar and unfamiliar faces in sheep using a 2-way discrimination task. Of particular interest were effects of lateralisation and the differential use of internal (configurational) vs external features of the stimuli. Animals were trained in a Y-maze to identify target faces from pairs, both of which were familiar (same flock as the subjects) or both of which were unfamiliar (different flock). Having been trained to identify the rewarded face a series of stimuli were presented to the sheep, designed to test for the use of each visual hemifield in the discriminations and the use of internal and external facial cues. The first experiment showed that there was a left visual hemifield (LVF) advantage in the identification of [`]hemifaces', and [`]mirrored hemifaces' and [`]chimeric' faces and that this effect was strongest with familiar faces. This represents the first evidence for visual field bias outside the primate literature. Results from the second experiment showed that, whilst both familiar and unfamiliar faces could be identified by the external features alone, only the familiar faces could be recognised by the internal features alone. Overall the results suggest separate recognition methods for socially familiar and unfamiliar faces, with the former being coded more by internal, configurational cues and showing a lateral bias to the left visual field.

Abstract: Summary For humans, facial expressions are important social signals, and how we perceive specific individuals may be influenced by subtle emotional cues that they have given us in past encounters. A wide range of animal species are also capable of discriminating the emotions of others through facial expressions [1, 2, 3, 4, 5], and it is clear that remembering emotional experiences with specific individuals could have clear benefits for social bonding and aggression avoidance when these individuals are encountered again. Although there is evidence that non-human animals are capable of remembering the identity of individuals who have directly harmed them [6, 7], it is not known whether animals can form lasting memories of specific individuals simply by observing subtle emotional expressions that they exhibit on their faces. Here we conducted controlled experiments in which domestic horses were presented with a photograph of an angry or happy human face and several hours later saw the person who had given the expression in a neutral state. Short-term exposure to the facial expression was enough to generate clear differences in subsequent responses to that individual (but not to a different mismatched person), consistent with the past angry expression having been perceived negatively and the happy expression positively. Both humans were blind to the photograph that the horses had seen. Our results provide clear evidence that some non-human animals can effectively eavesdrop on the emotional state cues that humans reveal on a moment-to-moment basis, using their memory of these to guide future interactions with particular individuals.

Abstract: Contraceptive management of publicly valued wildlife species requires safeguards to ensure that these populations are preserved in a healthy state. In addition, reversibility of contraceptive effects and safety in pregnant animals are major concerns. A population of wild horses has been immunized against porcine zona pellucida (PZP) over a 12 year period on Assateague Island National Seashore, MD (ASIS). Mares initially received one or two 65 microg inoculations and once a year 65 microg booster inoculations, all delivered by dart. All young mares aged > 2 years were treated with PZP for 3 consecutive years regardless of whether they have bred successfully and they were then removed from treatment until they had foaled. All mares vaccinated for 1 or 2 consecutive years became fertile again and 69% of mares treated for 3 consecutive years returned to fertility. All five mares treated for 4 or 5 consecutive years have also returned to fertility, but over longer periods of time. Mares treated for 7 consecutive years have not returned to fertility, but several, while still infertile, have started ovulating again. There was no difference in survival rates between foals born to treated and untreated mares, and PZP treatment of pregnant mares did not affect subsequent fertility of their female offspring.