The Mating System
The cotton-top tamarin has a monogamous mating system with cooperative breeding. However, it has been found that not all groups of cotton-top tamarins’ are monogamous. In a rare occasion reported by researchers, there was two pregnant females within a social group. It is possible that the two copulations occurred as a result of competition for “reproductive sovereignty”, or the process of reproductive suppression failed in that case (Savage, 1990).
It is common for female tamarins to give birth to non-identical twins twice a year in the wild (Bridgeman, 2002). On average, it has been found that 80% of births produce twins. Cotton-top tamarins care for their young for about 8 weeks after birth and the young reach sexual maturity around 18 months for females and 24 months for males (Massicot, 2005). Additionally, they have an estrus cycle of 15 days and gestation lasts approximately 140 days (Bridgeman, 2002). The female ovulatory cycle is maintained by the presence of males; however, these males are never the female’s brothers (Savage, 1990). Such implications suggest that heterozygosity within the tamarin’s genes is important.
Within the cotton-top tamarin social group, the father, siblings, and subordinates care for the young. It is crucial for both males and females to get experience caring for the young because both sexes are involved in care-taking. The ability to care for the young is not an instinctual behavior it is learned. The care of the young by subordinates is important because breeding female tamarins face several energetic cost of reproduction (Savage, 1990). The infants are about 20 to 30 % of their mother’s weight. In addition, it is common for the mother to go through estrus weeks after she gives births which increases her chances of being pregnant while nursing her new-born (Savage, 1990). The energetic costs on the mother are very high, so she needs the assistance of her social group to raise the young.
Image courtesy of Lynn Davis
Within the mating system, females depend on male assistance because they need the male to help raise the young. As a result, the male is shown a lot of attention by females in order to establish a pair bond. When female tamarins are placed within the periphery of an unknown male tamarin, it has been observed that they increase their “affiliative behavior, copulations, and scent marking”. It is common to observe large amounts of contact, social huddling, and grooming between the pair. Male tamarins are groomed the most within the social group. In addition, it has been observed that juveniles play with each other more than adults. An increase in affiliative behavior is important in the establishment of pair bonds. Once the pair bonds are established, there is a decrease in affiliative behavior and the pair dedicates more time in caring for the young. However, their pair bond is still visible in territorial defense (Savage, 1990).
The behavior of male and female cotton-top tamarins exhibit little sexual dimorphism, but they differ greatly in behavior. Nevertheless, there are conflicting views about the differences in behavior among the sexes. Some researchers observed that males initiate contact, groom, and sniff their mates more than females. However, other researchers have found that there is no difference in the affiliative behavior but females initiated sexual behavior more than males (Savage, 1990).
