Variations in the predictability of a stressor have pronounced effects on the behavioural and physiological effects of stress in rats. It is reasonable to expect that variations in the predictability of husbandry routines thought to be aversive to animals might have similar effects on stress indices. Similarly, variations in the predictability of positive events, of which feeding is an obvious example, may affect welfare. This review examines the behavioural and physiological effects of the predictability of aversive and appetitive stimuli, and the application of experimental findings to animal husbandry in practice. It is argued here that two distinct but overlapping types of predictability exist. 'Temporal' predictability describes whether an event occurs at fixed or variable intervals, whereas 'signalled' predictability relates to the reliability of a signal preceding the event. This review examines the effects of each of these types of predictability in relation to positively and negatively perceived events, and examines the link between predictability and control. Recommendations are made for relatively simple and inexpensive modifications to husbandry routines that may be easy to incorporate into the schedules of busy staff yet could have a profound impact on the welfare of animals in their care.

Male animals of many species use conspicuous coloration to attract mates. Among mammals, primates possess the most brilliant secondary sexual coloration. However, whether colour plays a part in primate female mate choice remains unknown. Adult male rhesus macaques undergo a hormonally regulated increased reddening of facial and anogenital skin during their mating season. We experimentally investigated whether red male facial coloration is preferred by simultaneously presenting female rhesus macaques (n = 6) with computer-manipulated pale and red versions of 24 different male faces. The duration and direction of gaze were measured to discern visual preferences. Females exhibited preferences for the red versions of male faces. It is proposed that male coloration might provide a cue to male quality.

Species comparisons of personality structure (i.e. how many personality dimensions and the characteristics of those dimensions) can facilitate questions about the adaptive function of personality in nonhuman primates. Here we investigate personality structure in the brown capuchin monkey (Sapajus apella), a New World primate species, and compare this structure to those of chimpanzees (Pan troglodytes), orangutans (Pongo spp.), and rhesus macaques (Macaca mulatta). Brown capuchins evolved behavioral and cognitive traits that are qualitatively similar to those of great apes, and individual differences in behavior and cognition are closely associated with differences in personality. Thus, we hypothesized that brown capuchin personality structure would overlap more with great apes than with rhesus macaques. We obtained personality ratings from seven sites on 127 brown capuchin monkeys. Principal-components analysis identified five personality dimensions (Assertiveness, Openness, Neuroticism, Sociability, and Attentiveness), which were reliable across raters and, in a subset of subjects, significantly correlated with relevant behaviors up to a year later. Comparisons between species revealed that brown capuchins and great apes overlapped in personality structure, particularly chimpanzees in the case of Neuroticism. However, in some respects (i.e. capuchin Sociability and Openness) the similarities between capuchins and great apes were not significantly greater than those between capuchins and rhesus macaques. We discuss the relevance of our results to brown capuchin behavior, and the evolution of personality structure in primates.

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Increasing evidence suggests that personality structure differs between species, but the evolutionary reasons for this variation are not fully understood. We built on earlier research on New World monkeys to further elucidate the evolution of personality structure in primates. We therefore examined personality in 100 family-reared adult common marmosets (Callithrix jacchus) from three colonies on a 60-item questionnaire. Principal components analyses revealed five domains that were largely similar to those found in a previous study on captive, ex-pet, or formerly laboratory-housed marmosets that were housed in a sanctuary.The interrater reliabilities of domain scores were consistent with the interrater reliabilities of domain scores found in other species, including humans. Four domains---conscientiousness, agreeableness, inquisitiveness, and assertiveness---resembled personality domains identified in other nonhuman primates. The remaining domain, patience, was specific to common marmosets. We used linear models to test for sex and age differences in the personality domains. Males were lower than females in patience, and this difference was smaller in older marmosets. Older marmosets were lower in inquisitiveness. Finally, older males and younger females had higher scores in agreeableness than younger males and older females. These findings suggest that cooperative breeding may have promoted the evolution of social cognition and influenced the structure of marmoset prosocial personality characteristics.