Reproduction in the vervet monkey (Cercopithecus aethiops): I. Testicular volume, testosterone, and seasonality

Abstract

To test whether the male could contribute to the birth peak seen in both wild and captive vervets, testicular volume and peripheral testosterone concentration were measured monthly in nine adults throughout a 14‐month period. Volume was an average of 15% greater during the months of June to September, the period of natural breeding activity in the wild, than at other times of the year. Testosterone concentration rose throughout the time period but did not correlate with testicular volume. Quarterly biopsies of the right testis in animals either used for or withheld from breeding revealed the presence of spermatozoa and the existence of spermatogenesis throughout the year. There was no correlation of testicular volume with breeding status or biopsy. If these results from individually caged animals are representative of group‐caged and wild animals, then such small seasonal changes are unlikely to affect year‐round breeding. Therefore, a physiological contribution by the male to natural birth peaks seen in the wild and captivity is not readily apparent.

Anthropogenic food enhancement alters the timing of maturational landmarks among wild savanna monkeys (Chlorocebus pygerythrus)

“…Along with an earlier significant increase 421 in body mass, peri-pubertal males in !Gariep show significantly larger relative testis volume than 422 in Soetdoring in dental ages 5 and 6 (Fig 3), ultimately leading to similar relative testis volumes 423 by adulthood. Increases in testosterone levels accompanied by a 15% increase in testis volume 424 in captive vervets during the breeding season suggest that a larger testis volume may confer a 425 higher chance of fertilization (Eley et al 1986;Eley 1992). Sample collection was limited to June 426 through August, which is just after the peak breeding season, characterized as April to June 427 throughout South Africa (Blaszczyk 2016;McFarland et al 2014).…”

Morphometric data for adult lion‐tailed macaques (Macaca silenus)

“…Morphometric data from nonhuman primate species have been used for a variety of purposes. These have included basic applications, such as establishment of normative growth rates, studies of the effects of nutrition or rearing conditions on development (Fooden and Izor, 1983;Glassman and Coelho, 19881, documentation of sexual maturation (Dixson et al, 19801, and tracking of morphological changes related to breeding seasonality (Eley et al, 1986;Glick, 1979;Sade, 1964). Other a plications have inle, morphometric sexual dimorphism has Eeen related to a variety of ecological and social variables among primate species (Glutton-Brock et al, 1977;Kenagy and Trombulak, 1986; Leuteneg er and Kelly, among variables such as testes size, bo y size, and breeding systems have generated hypotheses regarding mating competition and sexual selection in nonhuman primates (Harcourt et al, 1981;Harvey and Harcourt, 1984;Moller, 1988).…”