Older maternal age is associated with relatively higher risks of perinatal mortality/morbidity, although the absolute rate of such outcomes is low.

Demography provides critical data to increase our understanding of the evolution, ecology, and conservation of primate populations. The chimpanzees of the Mahale Mountains National Park, Tanzania, have been studied for more than 34 yr on the basis of individual identification and standardized attendance records. From this long-term study, we derived the following demographic data: The major cause of death was disease (48%), followed by senescence (24%) and within-species aggression (16%). Fifty percent of Mahale chimpanzees died before weaning. The median ages of female life history variables were: first maximal swelling, 10.0 yr (n = 5); emigration, 11.0 yr (n = 11); and first birth, 13.1 yr (n = 5). The median period of adolescent infertility was 2.8 yr (n = 4) when calculated from the age at immigration to that at first birth. Female fecundity was highest between 20 and 35 yr of age, with an annual birth rate of 0.2. Twenty-six females that were observed from a young age (10-13 yr) to death at various ages (15-40 yr) gave birth to an average of 3.9 and weaned an average of 1.4 offspring. Twenty-five females that were observed from middle age (18-33 yr) to death in older age (31-48) gave birth to an average of 2.7 and weaned an average of 2.0 offspring. The post-reproductive lifespan for female chimpanzees was defined as the number of years that passed from the year when the last offspring was born to the year when the female died, minus 5. Twenty-five percent of old females had a post-reproductive lifespan. The interbirth interval after the birth of a son (x = 72 mo) tended to be longer than that after the birth of a daughter (x = 66 mo). The extent of female transfer, which is a rule in chimpanzees, is influenced by the size and composition of the unit group and size of the overall local community.

ABSTRACT. A longitudinal study of nematode infection in chimpanzees was conducted between 1989 and 1994 on the M group chimpanzees of the Mahale Mountains National Park, Tanzania during two annual dry and rainy season periods and a third rainy season. Chemical and physical antiparasite properties of medicinal plant use against the strongyle nematode Oesophagostomum stephanostomum have recently been reported at Mahale. Here, the incidence of nematode infections were analyzed for seasonal trends to elucidate the possible influence of parasite infection on previously reported seasonality of medicinal plant use and to test the hypothesis that the use of these plants is stimulated by O. stephanostomum. The number of chimpanzees infected by O. stephanostornum was significantly higher in the rainy season than in the dry season of both 1989-1990 and 1991-1992. However, the incidence of Trichuris trichiura and Strongyloides fuelleborni showed no seasonality. Reinfection of individuals by O. stephanostomum occurred in synchrony with annual variation in rainfall: there was a sharp rise in the occurrence of new infections per individual within one to two months after the beginning of the first heavy rains of the season. This pattern coincides with the reproductive cycle of this nematode species. O. stephanostomum (95~ infections were associated significantly more frequently with medicinal plant use than either T. trichiura (50~ or S. fuelleborni (40~ infections. These observations are consistent with previous reports for the increased use of these plants during the rainy season and are consistent the hypothesis that medicinal plant use is stimulated by O. stephanostomum infection.

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This population-based, retrospective cohort study of very low birth weight infants was undertaken to: 1) identify factors associated with nonattendance for follow-up, 2) estimate the prevalence of cerebral palsy at age > or = 18 months, and 3) model the prognostic association between prenatal and perinatal risk markers and cerebral palsy. The sample included 496 surviving very low birth weight infants born in 32 hospitals in Southwest Ontario between January 1982 and December 1986. Multivariate analyses were performed using the proportional odds regression model. Loss to follow-up was more likely among those with mothers < 20 years of age, those with unmarried mothers, and those not born in a tertiary center. Loss to follow-up was less likely for those with neonatal anemia and those of lower birth weight. Motor development of the 369 children who were followed at least 18 months was classified into one of three categories: normal, suspect, or cerebral palsy. Multivariate analysis revealed that factors predictive of poorer outcome were intraventricular hemorrhage, unmarried mother, male sex, recurrent apnea, and hydrocephalus. The finding that unmarried status was associated with loss to follow-up and was also an important predictor of cerebral palsy suggests that it is important for follow-up clinics to identify ways of assisting this population to remain in contact with the clinic.