Females of both species of chimpanzee, Pun troglodytes and P. paniscus, exhibit conspicuous anogenital sex swellings that are useful external markers for assessing ovarian cyclicity. A new, quantitative method for describing these swelling cycles was refined during laboratory studies of four P. paniscus and nine P. troglodytes and was used to analyze variability in swelling patterns. Clear-cut anatomical changes of the perineum were found to have both interindividual and interspecific reliability. The swollen phase of the cycle was defined as the period when the medial surfaces of the labia minora are pressed against each other so the aperture leading to the vagina appears as a slit (labial occlusion). When defined with this precision, comparisons within and between the species revealed two types of cycle for both species; swollen phases of P. puniscus were about 24 or 39 days in duration, on average, whereas those of P. troglodytes were about 14 or 18 days. Urine samples from the P. troglodytes were collected and analyzed for luteinizing hormone (LH) (34 cycles), estrone glucuronide (E,G), and pregnanediol-3-glucuronide (PdG) (18 cycles). When the two types of cycle were separated in analysis, it was found that the day when labial occlusion occurred served as a predictor of the preovulatory LH peak in the cycles with a long swollen phase. Levels of E,G correlated closely with swelling scores in multiparous females regardless of phase lengths, suggesting that the new swelling scores are a reliable indicator of E,G excretion in multipara. Cycles with long swollen phases had relatively high levels of PdG during the luteal phase, whereas cycles with short swollen phases had relatively low levels of PdG and a shorter luteal phase. The marker of labial occlusion and the duration of the preswollen phase defined by the marker appear to be potentially useful in studies of reproduction in Pan, for monitoring female fertility, and in artificial insemination procedures. If it is confirmed that swelling pattern predicts progesterone levels during the luteal phase, it would make interventions possible in the case of low levels so that a potential pregnancy could be maintained to term.
Genetic mechanisms have been proposed to explain the pervasive representation of right-handedness in humans, whereas random, nongenetic factors have been posited to explain the lack of population-level right-handedness in nonhuman primates. We report evidence that hand preferences in chimpanzees are heritable, even among related individuals raised in different environments. Furthermore, we report that the degree of heritability is modified by factors associated with developmental instability, notably, offspring parity. The data are interpreted to reconcile both genetic models for handedness and hypotheses suggesting that developmental instability influences variation in handedness.
The relationship between sex hormone concentrations and female genital swelling during the menstrual cycle in the monogamous gibbon was comparable with that of polygamous female primates, such as the chimpanzee, which live in multimale groups and have larger swellings. The data, therefore, support the hypothesis proposed by C. R. Carpenter more than 50 years ago, that the gibbon's genital swelling, like that of other female primates, reflects basic physiological processes associated with progress of the menstrual cycle. Genital swelling increased during the follicular phase with increasing concentrations of oestradiol and oestrone glucuronide, reached maximal swelling in association with the mid-cycle peaks in the oestrogens and LH and began detumescence with the initial increases in progesterone during the luteal phase. The data also suggest that the menstrual cycle of the gibbon is shorter than previously reported, since cycles of 19-22 days exhibited hormone patterns that are consistent with ovulation. The genital swelling of the female gibbon is a useful marker for monitoring progress of the menstrual cycle and the presumptive time of ovulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.