Abstract: 1. 1. The communication performance of 12 rhesus monkeys was investigated in a situation in which the rewards of both members of a pair of monkeys could not exceed chance levels unless the operator monkey responded to cues provided by the informant monkey which indicated the location of food. Each member of the pair was trained in both operator and informant roles in different phases of the experiment. Communication performance improved progressively to levels consistently above chance. However, communication learning appeared to be specific to the role in which the individual was trained, and when roles were reversed no evidence of transfer was obtained. Tests of foodsharing behaviour showed a substantial increase in the tendency to share food with the partner following communication training. This occurred however, only when the partner was the only social stimulus present; if another monkey was also present there was no evidence of preferential responses to the partner. In all phases of communication training, monkeys which were housed together performed more efficiently than did monkeys housed individually.2. 2. The acquisition of stimulus-producing responses was investigated by causing an opaque screen to remain in front of the informant unless the operator monkey pulled a vertical lever at the front of its restraining cage. Initially, operators responded immediately to the foodcarts, but with further testing there was a steady increase in the tendency to defer the response to the food-carts until the lever had been pulled, revealing the informant monkey.3. 3. Transfer of communication training was tested with new monkey informants, and with two inanimate stimuli, a mechanical puppet, and a stationary plaque. The latter two objects were placed behind the rewarded food-carts before each trial. There was clear evidence of positive transfer to each of these conditions, but marked differences among conditions were obtained. Performance with the monkeys averaged 76 per cent. correct, as compared with 62 and 40 per cent., with the puppet and the plaque, respectively.4. 4. To test the ability of trained operator monkeys to select the appropriate informant on the basis of behavioural cues, the communication situation was arranged so that two informant monkeys were present on all trials. However, on any trial only one of these informants could be rewarded, and the operator's rewards were contingent upon delivering food to this informant. Efficiency of discrimination began at approximately 45 per cent, (chance = 25 per cent. and improved progressively to levels above 75 per cent.

Abstract: We tested the responses of Bufo marinus to prey stimuli of varying visual complexity that were moved around the toads in either a clockwise or anticlockwise direction at 1.7 revolutions/min. Predatory responses directed at prey resembling an insect were frequent when the model insect moved clockwise across the visual midline into the right visual hemifield. In contrast, the toads tended to ignore such stimuli when they moved anticlockwise across the midline into the left hemifield. No such lateralization was found when a rectangular strip moved along its longest axis was presented in a similar way. The toads also directed more responses towards the latter stimulus than towards the insect prey. Hence, the results suggest that lateralized predatory responses occur for considered decisions on whether or not to respond to complex insect-like stimuli, but not for decisions on comparatively simple stimuli. We discuss similarities between the lateralized feeding responses of B. marinus and those of avian species, as support for the hypothesis that lateralized brain function in tetrapods may have arisen from a common lateralized ancestor.

Abstract: Models of inter-sexual selection generally assume heritable variation in mating preferences among females within populations. However, little is known about the nature of such variation. The aim of this study was to characterize quantitatively the phenotypic variation in female preference for a sexually selected male trait, body colour pattern, within a population of the Trinidadian guppy, Poecilia reticulata. Significantly more female guppies preferred the more brightly coloured of two similar-sized males presented simultaneously as potential mates. Mating preference scores for individual females were significantly and positively correlated between two repeated trials on successive days. Females were thus individually consistent in their particular choice of mates, and the calculated repeatability of their mating preference was relatively high. Notwithstanding the aforementioned, significant variation existed among females in the degree of their preference for brightly coloured males. Individual mating preference scores were not normally distributed, but were rather skewed to the right (i.e. towards greater values). These results suggest that additive genetic variation for mating preferences based on male colour pattern is maintained, and the opportunity for the further evolution of both bright male colour patterns and female preference for this trait appears to exist in the study population from the Quare River, Trinidad.

Abstract: Adrenal glucocorticoid (GC) secretion is an important component of the response to stress in vertebrates. A short-term increase in circulating GCs serves to redirect energy from processes that can be briefly curtailed without harm, allowing energy to be directed towards eliminating or avoiding the stressor. In contrast, prolonged elevation of GCs can cause a broad range of pathologies, including reproductive suppression. We examined whether social subordination in wolves leads to chronically elevated GC levels, and whether this [`]social stress' causes reproductive suppression of subordinates in cooperatively breeding species. Behavioural and endocrine data collected over 2 years from three packs of free-living wolves in Yellowstone National Park did not support this hypothesis. GC levels were significantly higher in dominant wolves than in subordinates, for both sexes, in all packs, in both years of study. Unlike other cooperatively breeding carnivores (e.g. dwarf mongooses, Helogale parvula, and African wild dogs, Lycaon pictus), high GCs in dominant wolves were not associated with high rates of aggression or agonistic interaction. Aggression increased for wolves of all ranks during mating periods, accompanied by a significant rise in GC levels. If chronic elevation of GCs carries fitness costs, then social stress in wolves (and many other social species) is a cost of dominance, not a consequence of subordination. The specific behavioural correlates of dominance that affect GC levels appear to vary among species, even those with similar social systems.