Are Eulemur species pair-bonded? Social organization and mating strategies in Eulemur fulvus rufus from 1988-1995 in southeast Madagascar.

Strong social relationships have been reported between adult male and female prosimian primates in the genera Eulemur and Varecia and have been referred to as "pair-bonding." It has been hypothesized that females benefit from these affiliative relationships with an adult male by having protection against infanticidal males, implying that the male member of the dyad also is the father of her offspring. I evaluated this hypothesis and whether or not the term pair-bond was appropriate by using field data collected on two groups of Eulemur fulvus rufus in southeastern Madagascar. Four predictions were tested: 1) male-female dyads will be stable throughout the year, 2) male-female dyads will be more prevalent during the mating season, and/or the birth season when infants would be most vulnerable to infanticide, 3) females should copulate either exclusively or most often with their male dyad partner than with other males during the mating and/or birth season, and 4) rates of aggression will be higher between males or between females and males who are not their dyad partner. Predictions 1, 2, and 3 were not supported and Prediction 4 was only partially supported. Adult male-female dyads however, were more prominent in feeding contexts during the mating season and food scarcity periods. Most aggression occurred during feeding between males and nondyad group members. Since female feeding rates were often higher when feeding near male dyad partners, adult male-female dyads may serve as a way of increasing foraging efficiency for the female, which in turn may influence reproductive success. All males who were dyad partners also copulated first and more frequently with all females. It is suggested that "dyad" is a better descriptive term than pair-bonding for the social patterns observed since dyads were comprised of same-sex individuals, were temporary, and did not exclusively serve a reproductive function.