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.

Abstract: The experiments investigated how two adult captive chimpanzees learned to navigate in an automated interception task. They had to capture a visual target that moved predictably on a touch monitor. The aim of the study was to determine the learning stages that led to an efficient strategy of intercepting the target. The chimpanzees had prior training in moving a finger on a touch monitor and were exposed to the interception task without any explicit training. With a finger the subject could move a small “ball” at any speed on the screen toward a visual target that moved at a fixed speed either back and forth in a linear path or around the edge of the screen in a rectangular pattern. Initial ball and target locations varied from trial to trial. The subjects received a small fruit reinforcement when they hit the target with the ball. The speed of target movement was increased across training stages up to 38 cm/s. Learning progressed from merely chasing the target to intercepting the target by moving the ball to a point on the screen that coincided with arrival of the target at that point. Performance improvement consisted of reduction in redundancy of the movement path and reduction in the time to target interception. Analysis of the finger's movement path showed that the subjects anticipated the target's movement even before it began to move. Thus, the subjects learned to use the target's initial resting location at trial onset as a predictive signal for where the target would later be when it began moving. During probe trials, where the target unpredictably remained stationary throughout the trial, the subjects first moved the ball in anticipation of expected target movement and then corrected the movement to steer the ball to the resting target. Anticipatory ball movement in probe trials with novel ball and target locations (tested for one subject) showed generalized interception beyond the trained ball and target locations. The experiments illustrate in a laboratory setting the development of a highly complex and adaptive motor performance that resembles navigational skills seen in natural settings where predators intercept the path of moving prey.