Behavioural, pharmacological, and physiological evidence supports an association between displacement activities and anxiety in macaques. Information is scarce in other primate and non-primate species. This study contributes to the understanding of the relation between displacement activities and emotional states by investigating the correspondence between self-directed behaviour and an inherently stressful situation in chimpanzees (Pan troglodytes). Data were collected on 81 captive chimpanzees housed in conditions varying from indoor single caging to indoor/outdoor enclosures containing up to 14 individuals. Observation of gentle and rough scratching, self-grooming, and yawning were used to test predictions concerning the response of individuals to neighbour vocalisation (i.e. the calls and noisy displays produced by neighbouring groups of chimpanzees), which has been previously demonstrated to increase the likelihood of intragroup agonistic behaviour. In socially-housed chimpanzees rough and gentle scratching and yawning were significantly more common after neighbouring individuals vocalised or displayed than before, but the effect lasted longer for rough-scratching. In addition, during periods characterised by higher levels of neighbour vocalisation, socially-housed chimpanzees performed rough scratching at higher rates. Self-grooming was not affected by the level of neighbour vocalisation. Single-caged chimpanzees, for whom neighbour vocalisation carries no risk of aggression by group members, showed no increase in self-directed behaviour when neighbour vocalisation level was high, suggesting that the risk of intra-group aggression, rather than neighbour vocalisation itself, elicits anxiety. While our study suggests that rough scratching is the most reliable indicator of anxiety in chimpanzees in the context of neighbour vocalisation, it also provides evidence that gentle scratching and yawning can be considered displacement activities in this species.

The emerging paradigm that MSCs are immune privileged has fostered the use of “off-the-shelf” allogeneic MSC-based therapies in human clinical trials. However, this approach ignores studies in experimental animals wherein transplantation of MSCs across MHC boundaries elicits measurable allo-immune responses. To determine if MSCs are hypo-immunogeneic, we characterized the immune response in rhesus macaques following intracranial administration of allogeneic vs. autologous MSCs. This analysis revealed unambiguous evidence of productive allo-recognition based on expansion of NK, B and T cell subsets in peripheral blood and detection of allo-specific antibodies in animals administered allogeneic but not autologous MSCs. Moreover, the degree of MHC class I and II mismatch between the MSC donor and recipient significantly influenced the magnitude and nature of the allo-immune response. Consistent with these findings, real-time PCR analysis of brain tissue from female recipients administered varying doses of male, allogeneic MSCs revealed a significant inverse correlation between MSC engraftment levels and cell dose. Changes in post-transplant neutrophil and lymphocyte counts also correlated with dose and were predictive of overall MSC engraftment levels. However, secondary antigen challenge failed to elicit a measurable immune response in allogeneic recipients. Finally, extensive behavior testing of animals revealed no main effect of cell dose on motor skills, social development, or temperament. Collectively, these data indicate that allogeneic MSCs are weakly immunogenic when transplanted across MHC boundaries in rhesus macaques and this negatively impacts durable engraftment levels. Therefore the use of unrelated donor MSCs should be carefully evaluated in human patients.

Introducing singly housed rhesus macaques (Macaca mulatta) into isosexual pairs is widely considered to improve welfare. The population of laboratory rhesus macaques is heterogeneous on a variety of factors and there is little literature available to directly evaluate the influence of many of these factors on the benefits of pair housing. Subjects were 46 adult female and 18 adult male rhesus macaques housed at the Tulane National Primate Research Center and the Yerkes National Primate Research Center. Behavioral data totalling 859 h and serum cortisol levels derived from 312 serum samples were analyzed for main effects of housing condition, comparing single housing to pair housing. In addition, a series of analyses were performed to test for interactions between housing condition and seven independent variables: sex, age, prior duration of single housing, presence or absence of a history of self-injurious behavior, and dominance rank, levels of affiliation and agonism in the paired setting. After the collection of 4–8 h of baseline data and three serum cortisol samples, pairs of individuals were introduced to one another and data collection was repeated, no earlier than 4 weeks after introduction. In pair housing both female and male subjects showed decrease in abnormal behavior (females: 54% reduction; P = 0.001; males: 18% reduction; P = 0.0007) and anxiety-related behavior (females: 35% reduction; P = 0.0001; males: 41% reduction; P = 0.0001), and increases in locomotion (females: 41% increase; P = 0.0001; males: 76% increase: P = 0.002). In pair housing, there were no significant sex differences in social behavior. Descriptively, paired females spent 12% of samples engaged in affiliative behavior and 0.5% engaged in agonistic behavior (back-transformed arcsin square root means). The corresponding values for males were 12% and 0.3%. No interaction effects were detected with any of the independent variables tested in this study. Cortisol values varied with sex but did not differ between housing conditions; no differences were detected when any of the above variables were included in the statistical model. Results support the general consensus among those studying the welfare of captive primates that social housing is a potent means for promoting behavioral indicators of the psychological well-being of laboratory primates. These results are of considerable practical significance and include information that refutes common perceptions about the unsuitability of males as socialization candidates, perceived negative

Pair housing of laboratory macaques is widely considered to lead to positive changes in well-

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