Sex and helping: reproductive strategies of breeding male and female cotton-top tamarins, Saguinus oedipus

Abstract

Female marmosets and tamarins typically give birth to twins, and appear to need considerable assistance from the male and from other group members if they are to rear the young successfully. To ensure that male help is available, females would be expected to increase the time they devote to the pair relationship shortly before birth. Males, however, should devote most time to their relationship with the female after birth, when she is most likely to conceive. These predictions were tested in a study of five captive pairs of cotton-top tamarins for 3 months before and 3 months after the birth of infants, a period covering the second half of pregnancy, lactation and postpartum oestrus. Female investment in the pair relationship, measured by grooming and promotion of proximity, was greatest shortly before birth, while male investment in terms of promotion of proximity and affiliative behaviour such as nuzzling was greatest during the first weeks postpartum. Females showed more proceptive behaviour and were more receptive to males' mounts before they gave birth than after, but were more attractive to the male after birth. These results confirmed the predictions, and suggested that female tamarins use strategies aimed at gaining male assistance in rearing infants, while males, in addition to investing in their current offspring, adopt strategies for maximizing their chances of fathering future offspring.