The brachial plexus in the chacma baboon (Papio ursinus)

Abstract: The brachial plexus in each of ten embalmed, mature chacma baboons was dissected to document the structure and branching pattern of this nerve plexus in this increasingly used research animal. In general, the brachial plexus in the chacma baboon was similar to the plexuses in the vervet and other Old World monkeys. However, several aspects were comparable to those observed in domestic animals. Thus the bipedal and quadrupedal abilities of the chacma baboon were reflected in the structure of its brachial plexus.     

Molar enamel thickness in the chacma baboon, Papio ursinus (Kerr 1792)

Modern humans exhibit increasing relative enamel thickness from M1 to M3. Some biomechanical (basic lever) models predict that the more distal molars in humans encounter higher occlusal forces, and it has been postulated that this provides a functional explanation for the observed gradient in relative enamel thickness. However, constrained three-dimensional models and experimental observations suggest that there is a reduction in bite force potential from M1 to M3, which would be consistent with the tendency for humans to reduce the size of the distal molars. In this regard, it has been postulated that the distal increase in enamel thickness is a consequence of crown size reduction; thus, it is unnecessary to invoke functional scenarios to explain this phenomenon. We assess these competing proposals by examining relative enamel thickness in a catarrhine primate (Papio ursinus) that exhibits crown size increase from M1 to M3. The molar row of P. ursinus is positioned relatively far forward of the temporomandibular joint, which results in the baboon being able to exert relatively greater muscle forces during posterior biting in comparison to modern humans. Thus, a significant distalward gradient of increasing enamel thickness would be expected in P. ursinus according to the hypothesis that posits it to be functionally related to bite force. The present study reveals no significant difference in relative enamel thickness along the molar row in P. ursinus. This finding lends support to the notion that the relatively thicker enamel of human distal molars is related primarily to their reduction in size. This carries potential implications for the interpretation of enamel thickness in phylogenetic reconstructions: the relatively thick molar enamel shared by modern humans and some of our fossil relatives may not be strictly homologous, in that it may result from different underlying developmental mechanisms.     

Inbreeding and reproductive success in a natural chacma baboon,Papio cynocephalus ursinus,population

Six of 19 male chacma baboons living in a natural environment in Botswana were born in troops where they attained alpha status. At least three of these six males sired young in their natal troops. Nine other paternal males were immigrants, hence they were more distantly related to their mates, who were all natal. Offspring of natal and immigrant parents survived equally well to 90 days. These observations suggest that for this and other mammalian species the evolutionary history of a population may determine inbreeding costs.     

The effects of captivity stress on the blood chemical values of the chacma baboon (Papio ursinus).

Baboons were trapped and transported to the colony within 3 days of being captured. Blood was collected on Tuesdays and Fridays for blood chemical determinations. The changes in albumin and globulin resulted in marked changes in the albumin: globulin ratio. Cholesterol values showed a sudden and marked drop and the values were still below normal at the end of 9 weeks. Blood sugar values increased to significantly elevated levels and marked changes occurred in the enzyme activity and plasma corticosteroid activity. Male and female animals differed in their response with regard to the values found in some parameters. A period of adaptation or conditioning of 8 weeks was found to be required for an animal to reach stability in its blood chemical values.     

Distribution and population estimate for the chacma baboon (Papio ursinus) in KwaZulu-Natal, South Africa

We report the current species distribution and population estimate for the chacma baboon (Papio ursinus) in KwaZulu-Natal Province (KZN), South Africa, based on an analysis of estimated area of occupancy and estimated home range size. This estimate suggests a total population size of approximately 11,000 individuals for KZN. Much of the province is uninhabited, with a density in occupied areas of approximately 1.8 animals per km(2). The current population size may be more than an order of magnitude smaller than historical population size. Chacma baboons now exhibit a highly fragmented and discontinuous distribution in KZN, with 58% of the population residing within protected areas, and more than half of these troops reside in areas >1,500?m above average sea level. The small population and highly fragmented distribution of chacma baboons in KZN, combined with rapidly increasing human population size and transformation of natural habitat, suggest this species requires greater conservation attention.     

The influence of physical and chemical restraint on the physiology of the chacma baboon (Papio ursinus)

The chacma baboon (Papio ursinus) is extensively used in South Africa for biomedical research. Being a large primate, it is always necessary to apply some measure of chemical or physical restraint. The physiological effects of placing an animal in a restraint chair are compared with the effects of various chemical agents, such as ketamine, halothane, and ketamine/xylazine combination over 90 min. It was found that ketamine and thiopentone infusion were a satisfactory chemical restraint agent that gave a stable physiological state over 90 min.     

Female perineal swelling and its effects on male sexual arousal: An apparent sexual releaser in the chacma baboon (Papio ursinus)

The function of the periodic perineal swelling that females of some primate species show in relation to their menstrual cycle has long puzzled many scientists. A role in female attractiveness was suspected, but fluctuations in female behaviors concomitant to these changes in female appearance have always prevented its assessment. By attaching a plastic reproduction of a fully swollen perineum to ovariectomized female chacma baboons, it has finally been demonstrated that the sexual swelling hasan important function in the sexual communication of this species. It induces sexual arousal in male conspecifics. The way the perineal swelling acts and other characteristic aspects of this feature appear to qualify it as a releaser for sexual behavior.     

Gastro-intestinal helminth parasites of the chacma baboon, Papio cynocephalus ursinus, from the coastal lowlands of Zululand, South Africa

An examination of 191 faecal samples from Papio cynocephalus ursinus from Mkuzi Game Reserve, Natal, South Africa, has revealed low prevalence rates for a high diversity of gastro-intestinal helminths. This high diversity, including the first evidence for an acanthocephalan infection in South African baboons, is compared to that from montane baboons studied previously.     

Rank and density correlates of inclusive fitness measures in a natural chacma baboon (Papio ursinus) troop

Some demographic characteristics of a group of chacma baboons (Papio ursinus)in a natural environment in northern Botswana were monitored for an 8-year interval. The group size ranged from 73 to 43 individuals. After 3 years at a high density, the group size declined over a 2-year interval, then stabilized again at reduced numbers (−41 %) and biomass (−40%) for over 2 years. The reduction in group size and biomass was followed by an increase in fecundity, greater for high-ranking than for low-ranking females. At the larger group size, survival was lower for infants born to low-ranking than to high-ranking females. Infant survival rates by female rank were equal at the lower density. The mean weight of adult females increased as the density decreased, but there was no correlation between female rank and body mass. We conclude that there is a negative relationship of density to individual condition and reproductive success and that there are fitness advantages to high female rank.     

Capture-release field observations of free-ranging chacma baboons,Papio ursinus,focusing on the behaviour of the sub-adult male segment of the baboon social unit

An adult female and three age-graded male chacma baboons,Papio ursinus, were captured and then artificially introduced into a recipient troop of free-ranging baboons of the same species. Two of the transplanted individuals, the youngest juvenile male and the sub-adult male, were accepted into the troop while the oldest juvenile male and the adult female were aggressively chased off by the sub-adult and adult males of the troop, and they subsequently returned more than 10 km to their home troop. Acceptance of the first two individuals was dependent on the gradual reduction of aggressive behaviour of the sub-adult males. This suggested that successful troop transfers in the wild, occurring more frequently than traditionally believed, may be at least partially contingent on the behaviour of the sub-adult male segment of the baboon social unit. Supported by a Graduate Research Grant from the University of Cape Town.     

An experimental examination of the colour component in visually mediated sexual arousal of the male chacma baboon (Papio ursinus)

Male chacma baboon ( Papio ursinus ) sexual arousal response as gauged by the coagulated seminal emissions resultant from masturbatory activity was experimentally assessed. Males were initially exposed to an ovariectomized female prior to and during daily oestradiol benzoate treatment. Males were then re-exposed to the same female prior to and during the wearing of a thermoplastic model of a swollen female perineum. A total of eight different colours were sequentially applied to the model. It was only the red model that elicited a response similar to that shown to the oestradiol-treated female. The behavioural data collected from the stimulus female supported the view that it was model colour that determined the differential male response.     

Bone loss in the ovariectomized baboon Papio ursinus: densitometry, histomorphometry and biochemistry

To develop a non-human primate model of systemic bone loss after ovariectomy, 24 ovariectomized (OVX) and eight control (non-OVX) female baboons Papio ursinus were investigated over a period of 48 months using bone mineral density (BMD), iliac crest bone histomorphometry, bone turnover markers, and variables of calcium metabolism. Lumbar spine (L1-L4) BMD measured by dual energy X-ray absorptiometry (DXA) decreased in OVX animals in the first 12 months (-7.6%) and showed a slow trend towards recovery after 24 months. Controls showed a slow increase in spinal BMD over 4 years (+9.7%). Total hip BMD decreased slowly up to 48 months in all animals (OVX -12.6%versus controls -10%); this indicated that OVX had a limited effect on total hip BMD. Forearm BMD did not change. The significant decrease in trabecular bone volume (TBV) of the iliac crest from baseline to 12 months was followed by some recovery. Microarchitectural deterioration of trabecular bone in OVX animals was demonstrated by a decline in trabecular number and an increase in trabecular spacing. These changes were also evident on sections of whole vertebrae, proximal femora and iliac crests. Changes in iliac TBV reflected spinal but not hip BMD changes in the OVX animals. Static and dynamic histomorphometric variables indicated that bone turnover was increased for 36 months following OVX. Controls showed no changes in histomorphometric variables. Bone specific alkaline phosphatase (ALPs) in OVX animals remained elevated throughout the study; osteocalcin (OC) was significantly elevated only at 6 and 12 months, and deoxypyridinoline (Pyr-D) was elevated at 12 months but declined after 24 months. ALPs was thus more sensitive to the long-term effects of OVX than were OC or Pyr-D. Controls showed no changes in bone turnover markers. This study showed consistent deleterious changes in lumbar BMD, bone histomorphometry with microarchitectural deterioration together with altered biochemical markers of bone turnover in the first 12 months after OVX. Since these changes resemble those in post-menopausal women, the non-human primate Papio ursinus is suitable for the study of bone loss in post-menopausal women.     

The glomerular filtration rate,effective renal plasma flow,and renal blood flow in the adult male chacma baboon (Papio ursinus)

Abstract: The radionuclide determination of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) has been validated in man, but not in the primate. GFR, ERPF, and renal blood flow (RBF) were measured in a group of 12 adult male chacma baboons using radiopharmaceuticals. GFR was determined using ^99mtechnetium-labelled diethylenetriamine-pentacetic acid. ERPF was measured with ¹³¹iodine-labelled hippuran. RBF, body surface area, and kidney weights were calculated using standard formulae. GFR was 49 ± 11 ml/min and ERPF was 237.9 ± 54.2 ml/min. Calculated RBF was 430.7 ± 111.9 ml/min and 507.4 ± 138.4 ml/min/100g of renal tissue. The results are in agreement with those obtained using more laborious nonradioisotopic techniques such as para-aminohippurate (PAH) and creatinine clearance and could serve as baseline normal values in the adult male chacma baboon.     

Observations on the ascending aortic fold in two chacma baboons (Papio hamadryas ursinus)

Baboons (Papio) were used to study the ascending aortic fold. The fold was present in two out of 20 hearts examined. Its position and shape was comparable to that observed in human subjects. The principal difference was the absence of paraganglia. The functional role of the baboon fold is unclear.     

Progressions of adult male chacma baboons (Papio ursinus) in the moremi wildlife reserve

It has been suggested that the sociospatial organization of baboon progressions has a protective function in which the most physically powerful troop members, the adult males, play a key role. This theory implies regularities in adult male progression order for different species of savannah baboons with similar social systems. Quantitative progression data are available from two such similar baboon species, olive and yellow, but not from the third, chacma. The order of movement of 15 adult male chacma baboons was determined from 40 progressions observed at the Moremi Wildlife Reserve, Botswana. The chacma males were most often found in the front sixth of progressions, next most often in the second sixth, and about equally often from there to the rear. As expected from the protection theory, this frontal positioning is consistent with available quantitative data from other species of savannah baboons.