Abstract: A group of six chimpanzees was placed in a social learning situation, without training. The learning task was an operant conditioning situation; that is, a subject had to pull two handles simultaneously to cause a piece of fruit to fall into the cage. Only three individuals acquired the operant behaviour. For the operant individuals, social influences on the expression of the learning task were then examined; the dominant chimpanzee during feeding had an inhibiting effect when close to the operant subjects. Depending on the subject, social factors may influence not only the specific expression of what is learnt, but also the nature of what is learnt. Chimpanzees appear to experience situations differently: they develop an individual problem-solving strategy according to their social relationships even if the experimental procedure is the same for all.

Abstract: There is evidence that female three-spined sticklebacks, Gasterosteus aculeatus L., prefer to mate with males whose nests contain eggs rather than with males with empty nests. While there is consensus on this point, a dispute exists about whether this preference should be attributed to a direct effect of the eggs on the female's entering the nest or, alternatively, to a positive impact of the eggs on the courtship behaviour and breeding coloration of the male. In the field experiment reported here females strongly preferred nests with eggs over empty nests. Additionally, females were less likely to enter risky nests with eggs: nests that contained fewer eggs than one average clutch or more eggs than the average nest content of parental males in this population. However, in the field possible differences in male attractiveness were not controlled for. In supplementary laboratory experiments the effect on female choice of possible changes in male attractiveness (intensified courtship and coloration) as a result of the presence of eggs in the nest was tested. Other differences in male attractiveness as a result of differences in male quality (body size, breeding coloration before the test, territory quality and size) were controlled for. When females had no access to the nests, they showed no preference for males with eggs in their nests in simultaneous choice tests. These results, together with the earlier published data, make it likely that the preference of females for nests with eggs is partly a direct consequence of the eggs themselves. So female sticklebacks are influenced by the mate choice behaviour of other females, but remain selective as to the actual nest content.

Abstract: Three methods were used simultaneously to determine the relationships between the vertical forces exerted on the hooves and the positions of the limbs and hooves at the times of peak vertical forces from 2 horses galloping on a track straightaway. Vertical forces were recorded from an instrumented shoe, fetlock joint motion was measured with an electrogoniometer and the angles of the carpus, fetlock and hoof were determined from slow-motion films. At hoof contact, the mean angles of the carpus and fetlock were 181-182 degrees and 199-206 degrees, respectively. Peak vertical forces on the heel occurred at or near maximum extension of the carpal and fetlock joints. Peak forces on the toe occurred during flexion of the fetlock joint and at mean hoof angles of 28-31 degrees from the horizontal. The mean angles of the hoof from the horizontal at the time of heel contact were 6-7 degrees. Hoof lift occurred at mean carpal angles of 173-174 degrees and mean fetlock angles of 199-200 degrees.

Abstract: Abstract. It is commonly suggested that the principal function of allogrooming is to reduce social tension between group members, but direct evidence of the physiological consequences of grooming at particular sites is lacking. By filming allogrooming sequences in a herd of Camargue horses, Equus caballus , their preferred grooming site, which lies on the lower neck, was identified. Experimental imitation of grooming at this site reduced the heart rate of the recipient while grooming on a non-preferred area did not, in both adults and foals. This preferred site lies close to a major ganglion of the autonomic nervous system.