Sifaka females give birth during the dry season, when little food is available. Pregnancy and the ensuing demands of lactation push lemur mothers to the nutritional edge. Male sifakas, scientists speculate, defer peacefully so that their mates and, more importantly, their potential offspring might survive. In species where females suffer fewer ecological hardships, males can get away with less chivalry. But even in species characterized by female harems, such as mandrills and gorillas, male dominance doesn t mean absolute control.
Females play the field, sneaking off for a tumble in the jungle with peripheral males.
In chimpanzees, whose troops include multiple adults of both sexes, females disappear for days at a time. Genetic fingerprinting shows that more than 50 percent of chimps are fathered by males outside the troop. Ambiguous paternity elicits wider male support for a female and her infant from the alpha male she s mated with publicly, and from any pretenders to the throne she s mated with surreptitiously. For bonobos, sex is a way of life, their version of the handshake. Bonobo researcher Frans de Waal estimates that 75 percent of bonobo sex has nothing to do with reproduction there s sex between males, between females, between juveniles, often to reduce tension over food competition.