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Identifying the causes of differential reproductive success is key to understanding natural selection and the forces of selection operating on animals. Here we present results from a 9-yr (2004-2012) study of female reproductive performance in relation to mother's age and rank, presence of immigrant males, rainfall, and fig fruit abundance in four groups of gray-cheeked mangabeys ( Lophocebus albigena) in Kibale National Park, Uganda. We found that females had a rank- and age-specific reproductive pattern, with high-ranking females maturing earlier, having their first births earlier, and exhibiting significantly slower reproductive aging than low-ranking females. We also found that both immigrant and resident males were associated with higher birth rates. Finally, we found that reproduction was aseasonal and did not correlate with rainfall, but that births correlated positively with the abundance of fruits of Ficus spp. Our results show broad similarities between arboreal, forest-dwelling gray-cheeked mangabeys and their more terrestrial, open habitat-dwelling papionin relatives in the importance of dominance rank in estrous cycle initiation, first reproduction, and reproductive aging. [ABSTRACT FROM AUTHOR]

Body condition and reproductive maturation are parameters of reproductive success that are influenced by sexual hormones rising in the circulation during the time of puberty. Various endocrine systems can be programmed by conditions experienced during early life. Stress for instance is supposed to be capable of influencing fetal development, leading to adjustments of offspring's later physiology. We examined whether prenatal stress (induced by exposure to strobe light) during early- to mid-gestation was capable of affecting later reproductive parameters in guinea pigs ( Cavia aperea f . porcellus). Therefore, we measured the levels of testosterone and progesterone from the age of day 12-124 in prenatally stressed (PS, n = 20) and unaffected control animals ( n = 24). Furthermore, we determined the timing of puberty and growth. Body weight development revealed significantly faster growth in PS females compared to control animals. The onset of first estrus was slightly earlier in PS females, however not significantly so. Cycle lengths and levels of progesterone differed between groups over the course of time with higher progesterone levels and more constant cycles among PS females compared to control females who displayed marked differences between first and subsequent cycles. Levels of testosterone did not differ between groups. We conclude that prenatal stress accelerates growth and maturity in females, but not in males. [ABSTRACT FROM AUTHOR]

We assessed ovarian and endocrine function in 86 adolescents over a six month period. Postmenstrual estrone (E1) and estradiol-17 beta (E2) levels, premenstrual FSH levels and pre- and postmenstrual LH, testosterone (T) and androstenedione (A) levels decreased as the frequency of ovulation increased, while premenstrual E2, progesterone (P) and 17 alpha-hydroxyprogesterone levels increased. Both right and left ovarian volume and the per cent of multifollicular ovaries decreased with an increase in the frequency of ovulation. In the premenstrual phase P values correlated significantly with frequency of ovulation for FSH (r = -0.43: P less than 0.001), LH (r = -0.36: P less than 0.01), T (r = -0.31: P less than 0.05) and A (r = -0.26: P less than 0.05). Our data suggest that in the postmenarcheal period the progressive loss of immature endocrine and ovarian characteristics (high LH, FSH, and androgen levels and enlarged, multifollicular ovaries) is linked to an increasing number of ovulations. Progesterone plays a major role in the development of cyclic function characteristic of adult maturity. [ABSTRACT FROM AUTHOR]