Number of ovulations in the marmoset monkey (Callithrix jacchus): relation to body weight, age and repeatability.

The relation between number of ovulations and body weight, age or maternal identity was examined in 69 ovarian cycles from 29 captive-born common marmoset monkeys (Callithrix jacchus). Specifically, we addressed the following questions: was there high repeatability of ovulation number? Most of the variation in ovulation number was within, rather than between subjects. Repeatability in number of ovulations was 0.081 (n = 20 females with 2-6 ovulatory cycles per female); was age related to number of ovulations? There was no relation between age and number of ovulations, either within or between subjects; and was weight related to number of ovulations? Weight was related to number of ovulations. When the relation between number of ovulations (1-2 versus 3-4) and weight was examined through a logistic regression, there was a significant relation. Also, of the 11 subjects which had a variable number of ovulations across cycles, 90.9% were heavier when ovulating 3-4 than when ovulating 2. These results are discussed as the basis for the proposal that callitrichid primates may have been selected for potential variation in reproductive output and that this variation may be related to energy availability.