Timing of Birth, Female Reproductive Success and Infant Sex Ratio in Semifree-Ranging Barbary Macaques (Macaca sylvanus)

Abstract

Examined were 5 years of data on the reproduction of a semifree-ranging population of Barbary macaques (Macaca sylvanus). In this seasonally breeding species – birth season: mid-March to beginning of August – primiparous 4-year-old females gave birth significantly later in the year than older primiparous and multiparous females, respectively. Multiparous females without an infant from the preceding season gave birth significantly earlier than females who had raised an infant. 88.4% of birth intervals were approximately 1 year, 11.6% about 2 years. Infant loss did not influence the length of the interbirth interval, but after the birth of the next surviving infant the interval was significantly longer. The interval following the 1st infant was significantly longer than after subsequent infants. After the birth of daughters primiparous females had markedly longer birth intervals than after the birth of sons. Infant mortality was 9.1%. Neonatal mortality was influenced by rank and parity of the mother and sex of the infant. Allomothering and aggression by older group members are thought to be the main causes of infant mortality. Female reproduction rates were not dependent on rank. High-ranking females, however, bore their 1st infant significantly earlier than low-ranking females. Low-ranking females had more daughters than sons, in high-ranking females the reverse was found. Differences from findings of other species are discussed with regard to differences in social organization and the reproductive strategies resulting from them.

Female-Biased Maternal Investment in Rhesus Macaques

“…Thus, the findings of this study provide little support for either the LRC or the MQ hypothesis. In fact, only one prediction of the LRC hypothesis was empirically supported, namely that interbirth intervals following daughters are longer than those following sons [8,9]. The finding that infant mortality was higher for males than for females is more consistent with the MQ than with the LRC hypothesis, and also with patterns of infant mortality in other polygynous mammals [1].…”

Development and sexual selection in primates

“…However, even after the first birth, adolescent females may not be as fertile as adult females, with longer interbirth intervals than fully -grown females, most likely because they still investing in their own growth or body condition to some extent (e.g. Paul & Thommen, 1984;Itoigawa et al, 1992;see below).…”

Social Factors Affect Secondary Sex Ratio in Captive Japanese Macaques

“…However, the evidence reported in the literature is conflicting. Several au thors have reported data supporting the Trivers-Willard model [3,[7][8][9], whereas re sults of other authors support the Local Re source Competition model [10][11][12], Further more, some studies did not support either of the two models [13][14][15][16][17][18][19][20].…”