Abstract
In the cooperative breeding system of cotton-top tamarin (TCB; Saguinus oedipus) "expectant" males gain weight during the last months of pregnancy of their partners as a way to cope with energy costs of reproduction. This phenomenon was described only in humans as a symptom of "Couvade syndrome". As after infants' birth, TCB male and female helpers lose weight, the same as fathers do, it might be expected that previously, they also gain weight. In 8 groups of TCB, we explored body weight changes of the three categories of individuals, in periods of six months, under three different reproductive conditions: control (no pregnancy and without offspring), pregnancy (pregnancy and without offspring), and raising (with offspring). We found that across pregnancy, TCBs increase their weight in the last trimester of that period while across breeding TCBs reduce their weight in the first trimester. Expectant males and also helpers could be preparing during pregnancy in relation to the weight losses they experience when raising their young.
