A comparative assessment of hand preference in captive red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos.

There are two major theories that attempt to explain hand preference in non-human primates-the 'task complexity' theory and the 'postural origins' theory. In the present study, we proposed a third hypothesis to explain the evolutionary origin of hand preference in non-human primates, stating that it could have evolved owing to structural and functional adaptations to feeding, which we refer to as the 'niche structure' hypothesis. We attempted to explore this hypothesis by comparing hand preference across species that differ in the feeding ecology and niche structure: red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos. The red howler monkeys used the mouth to obtain food more frequently than the yellow-breasted capuchin monkeys. The red howler monkeys almost never reached for food presented on the opposite side of a wire mesh or inside a portable container, whereas the yellow-breasted capuchin monkeys reached for food presented in all four spatial arrangements (scattered, on the opposite side of a wire mesh, inside a suspended container, and inside a portable container). In contrast to the red howler monkeys that almost never acquired bipedal and clinging posture, the yellow-breasted capuchin monkeys acquired all five body postures (sitting, bipedal, tripedal, clinging, and hanging). Although there was no difference between the proportion of the red howler monkeys and the yellow-breasted capuchin monkeys that preferentially used one hand, the yellow-breasted capuchin monkeys exhibited an overall weaker hand preference than the red howler monkeys. Differences in hand preference diminished with the increasing complexity of the reaching-for-food tasks, i.e., the relatively more complex tasks were perceived as equally complex by both the red howler monkeys and the yellow-breasted capuchin monkeys. These findings suggest that species-specific differences in feeding ecology and niche structure can influence the perception of the complexity of the task and, consequently, hand preference.

Coat condition, housing condition and measurement of faecal cortisol metabolites--a non-invasive study about alopecia in captive rhesus macaques (Macaca mulatta).

BACKGROUND: Previous studies have characterized alopecia in captive rhesus macaques (Macaca mulatta) by a mixed partial to complete alopecia in a bilateral symmetric pattern. METHODS: In this study, coat condition assessments were related to exogenous and endogenous factors in captive rhesus macaques under different housing conditions in order to identify disturbances in environmental factors controlling or influencing hair growth. Additionally, the degree of alopecia was investigated in relation to adrenal endocrine function as an indicator of social stress using faecal glucocorticoid measurements. RESULTS: Hair loss was found to vary with season and sex, was most pronounced in adult females during the winter and spring months. Generally, infants were not affected, but alopecia developed during adolescence. However, the housing system, available enclosure space and variations in group size and composition also appeared to influence coat condition. Levels of immunoreactive cortisol metabolites (11-oxoetiocholanolone) in faeces were significantly negatively correlated with alopecia, suggesting a relationship between hypothalamic-pituitary-adrenal (HPA) axis activity and hair loss in captive rhesus macaques. CONCLUSIONS: Although the present study demonstrates the influence of the HPA axis on coat condition, it is not known if hair loss is caused by abnormal behaviour or hormonal imbalances of the HPA axis itself. Our data suggest that alopecia in rhesus macaques is a highly complex multicausal disorder.

Early sexual maturity in male hamadryas baboons (Papio hamadryas hamadryas) and its reproductive implications.

We present data on sexual maturity in young hamadryas baboon males (Papio hamadryas hamadryas) and its reproductive consequences in a large captive baboon colony. Hamadryas baboons live in a multilevel social system, with one-male units (OMUs) as the smallest social entity. Male leaders of OMUs are believed to monopolize matings within their OMUs; hence mating is believed to be polygynous and monandrous. In a captive colony of hamadryas baboons, we found evidence that young males less than 4 years old fathered at least 2.5% of 121 offspring born subsequent to vasectomy of all adult males, and males aged 4-5 years fathered at least 16.5% of the offspring. Additional evidence that these young males are able to sire offspring came from a morphological comparison of sperm from hamadryas males of different ages. The sperm of a 48-month-old hamadryas baboon were morphologically indistinguishable from viable sperm from adult males, whereas sperm from a 45-month-old male showed some aberrations. If successful copulations by adolescent males constitute a regular pattern even in free-ranging hamadryas baboons, a hamadryas male's chances to reproduce would not be limited to his role as an OMU leader as previously assumed, and a male's reproductive career would consist of two phases: the adolescent phase, and the OMU leader male phase.

Dermatologic investigation of alopecia in rhesus macaques (Macaca mulatta).

Coat damage has been reported frequently in captive rhesus macaques (Macaca mulatta), and it is a serious health problem because the hair coat functions as an anatomic and physiologic barrier between the animal and the environment. The purpose of this study was to identify the pathogenesis of coat damage in this species and to exclude the most frequent causes of alopecia. The investigation included clinical, hematologic, bacteriologic, mycologic, parasitologic, and histopathologic evaluations. A broad systematic dermatologic investigation was performed on 156 rhesus macaques, kept under variable environmental conditions, at the German Primate Center, Göttingen. In addition, 27 animals from other primate facilities were incorporated into the study. Clinically, 126 animals showed partial alopecia of varying severity, with complete alopecia in the worst cases. In 88% of the cases, the disorder was bilaterally symmetrical. The back and extremities were most commonly affected. No gross clinical changes of the skin surface were detected. Histologic changes consisted predominantly of mild epidermal hyperkeratosis and mild perivascular dermatitis. The presence and severity of histologic lesions were not correlated to coat damage. Parasitic, bacterial, and mycotic causes of alopecia were ruled out. Overviewing these results, disturbances in environment and behavior controlling or influencing hair growth may lead to hair loss in captive rhesus macaques. Future studies should try to identify disturbances in extrinsic or intrinsic factors influencing hair follicle activity in rhesus macaques.

Food competition in captive female sooty mangabeys (Cercocebus torquatus atys).

We studied the social and foraging behavior of two captive groups of sooty mangabeys under two different spatial food situations. These food conditions were clumped (food was placed in a box) and dispersed (food was dispersed over the entire enclosure). In each group five adult females and two adult males were observed. As a criterion for food competition, individual differences in the relative food intake were used. Adult female mangabeys had a linear, stable, and unidirectional dominance hierarchy. Access to food was rank dependent among females only under clumped food distribution, as current models of the evolution of primate social systems predict. However, feeding success appeared to be mediated not by female but by male agonistic behavior toward females. High-ranking females received relatively less aggression from males and could, therefore, stay and feed longer in the feeding area. Male tolerance of higher-ranking females seems to mediate female feeding success under restricted food resources. The establishment of a special relationship with a high-ranking male might, therefore, be a strategy to get better access to food. This study demonstrates that female competition for access to food should not be analyzed separately from male influences on females and suggests that a more integral role of males in socioecological models of the evolution of primate social systems should be considered.