Demographic and descriptive studies at La Parguera, Puerto Rico.

The La Parguera facility was established in part to contrast the social behavior of free-ranging groups with that in enclosures, as well as to compare the seasonal events linked to reproduction with those at Cayo Santiago. Onset of breeding was correlated with onset of the rainy season at both sites. Male rank in new social groups was correlated with seniority, and males often joined groups containing older brothers. Dominant males had little influence on group movements or group rank. Maternal rank influenced the likelihood that male offspring would survive and reproduce: sons of dominant females had higher survival. High-ranking females and high-ranking groups produced more sons than daughters at birth. Observational techniques employed at La Parguera demonstrated the biases of using ad lib. field notes and the need to correct for observability of individuals as a function of their age, sex, and social rank. Although social behavior was qualitatively similar in enclosed and free-ranging groups, significant quantitative differences existed. During its 18 years of existence the La Parguera colony proved to be a fertile site for both descriptive and experimental studies. In this paper we briefly review behavioral and ecological findings from the free-ranging population, review the demographic analysis of a cohort of monkeys born early in the colony's history and followed until death, and, finally, focus on methodology in the study of free-ranging primates.

Food deprivation affects reproduction in adult female mice (Mus musculus) and the age of puberty for their female progeny.

Three experiments were designed to test the effects of food deprivation during various phases of the reproductive cycle on fertility and fecundity of the dams and on the age of sexual maturation and body growth of their female progeny. Food deprivation consisted of removal of all food every other day. Animals were deprived of food either during the period prior to pairing, during the period between pairing and conception or during gestation. Both fertility and fecundity were affected by food deprivation in some, but not all manipulations. The female progeny of food-deprived females reached puberty significantly later than the progeny of non-deprived dams when the food deprivation occurred during the week prior to pairing and up until successful insemination after pairing with a fertile male, but not when food deprivation occurred at other times during the reproductive cycle. Body growth did not differ in the daughters of food-deprived dams across the treatments for any of the experiments.

Food availability and secondary sex ratio variation in wild and laboratory house mice (Mus musculus).

Female house mice deprived of food intermittently for 1 week before mating gave birth to fewer male young, but litters of females deprived of food for 2 weeks did not differ from control litters. Since mean weights of females did not differ between the two treatments, our results suggest that females were initially stressed by food deprivation, but recovered in the second week.

Premating and gestational effects of maternal nutrition on secondary sex ratio in house mice.

Pregnant female house mice maintained on a consistent low-food diet give birth to a lower proportion of males than do control females fed ad libitum. Because house mice may experience daily fluctuations in food availability, we tested whether intermittent feeding during gestation influences the sex ratio of the offspring. In addition, we tested whether intermittent feeding has asymmetrical effects on the masses of adult male and female offspring. Females deprived of food every other day one week before mating and those deprived every third day during gestation produced a lower proportion of males than did control (fed ad libitum) females. Males born to females that were deprived of food during gestation had the same body mass at birth as males born to control females, but as adults their mass was lower than that of control males. There were no differences in the birth or adult body masses of female offspring. Because males of low body mass may have relatively low lifetime reproduction, our results support the Trivers-Willard model of sex ratio variation.