Abstract: We investigated the foraging producer-scrounger system of a captive flock of feral pigeons (Columba livia) by monitoring the number of food patches each individual produced. In one experiment, three different patch types were tested on the whole flock while, in a second, flock composition was varied for one patch type. In all cases we found non-uniform distributions of the number of patches produced per individual, which suggests the existence of producer and scrounger roles. This result could not be explained by either dominance or variability in individual learning ability. Individuals switched roles in response to changes both in food patch type and flock composition. These results are discussed in light of the skill pool hypothesis, which suggests that, in a group, different foraging specialists will profit by parasitizing each other's food discoveries.

Abstract: Individual differences in shading behaviour within a flock of sheep could be due to differences in thermoregulatory capabilities or to the influence of social factors. The possible influence of social factors on shade-use is examined in this paper. Two measures of dominance were made on 39 Merino wethers. These were based on the hierarchy determined by butting during feeding and on priority of access to limited feed. Leadership was also assessed while driving the sheep to a woolshed and as the sheep entered weighing scales. These behavioural traits were compared with leadership to shade and shade-use observed on 9 days during summer in a small pastureless enclosure containing natural shade. Maximum ambient temperature on these 9 days varied between 29.0 and 39.5[degree sign]C. All behavioural traits examined were significantly repeatable. The two dominance ranks were negatively correlated (P<0.05). The butting hierarchy was correlated with shading behaviour; those sheep that butted the larger proportion of the flock were seen to shade for longer periods of time (P=0.05). This relationship became more significant as environmental temperature increased. Significant (P<0.05) differences in the amount of time each sheep spent shading were evident throughout the flock, but in particular seven individuals shaded much less than others. Shade-use increased in hot weather and was slightly more strongly correlated with radiation load than with air temperature. The non-shading leadership ranks were related neither to each other nor to the leadership to shade. However, the sheep that moved to shade first remained there longest (P<0.05). Reduced motivation to feed did not appear to explain early movement to shade. Few overtly aggressive or other interactions between animals were seen to be associated with movements to or within shade. Nonetheless, the results indicate that social forces do exert some influence on shade-use.

Abstract: The structure of the play of colts and fillies living on pasture was studied from birth (n = 15) for up to 24 weeks. Foal play was categorized as running and bucking alone, running and bucking in a group, interactive (contact or combat) play, play with an object, and play at an adult. The rate of play decreased with increasing age and ambient temperature. Fillies and colts played with equal frequency, but engaged in some different types of play at different rates. There was no difference between colts and fillies in the proportion of play bouts of running and bucking in a group or playing with an object. Fillies engaged in running and bucking alone more than colts. Colts engaged in interactive play and play at an adult more than fillies. While there was no significant difference between colts and fillies in the duration of either type of running and bucking play, the interactive play bouts of colts were significantly longer than those of fillies. Both mares and stallions were tolerant of foal play which involved use of their body as a play object, including mounting play. Both fillies and colts engaged in mounting play. Foals used various natural objects found in the pasture for repeated bouts of play with inanimate objects, a behaviour which may explain, from a developmental perspective, the occasional use of “tools” in adult equids. The sex differences in type of play were consistent with the social structure of unmanaged adults in which males must compete with each other in order to associate with females.

Abstract: For the past decade, the Washington Park Zoo, Portland, Oregon, has had an active behavioral research program. The research department is both a zoo-supported research facility for visiting researchers and staff, and an educational facility that teaches practical behavioral research methods to undergraduates. The research education program utilizes students from any of a dozen local colleges and universities. Students receive academic credit for their participation. Active keeper-participation plays a major role in many research projects. Not only does keeper-cooperation facilitate research, but their knowledge of the individual animals often proves invaluable. In addition to involvement in student projects, keepers have also conducted their own research projects.

Abstract: A simulation model of grazing mechanics in ruminants shows that, due to the allometric relations of bite size and metabolic requirements to body size, small animals are able to subsist on shorter swards than large animals. (2) The density of nutrients in the grazed horizon of the modelled swards markedly affected the ability of animals of a given body size to satisfy their energy requirements. (3) By extension, the allometric relationships would be expected to apply in selective grazing and browsing species in their choice of food items of different size and nutrient content. (4) The results support the argument that sexual segregation and habitat choice of dimorphic species is an effect of scramble competition for limited resources, the males thus being excluded from mutually preferred swards. (5) The model provides an explanation for two interspecific phenomena amongst grazers: grazing succession and grazing facilitation.