Abstract
Starting with 4 pairs of marmosets, 204 young were successfully reared during 6 years. They were kept in family groups of 2-10. Litter size varied from 1-4; singletons (2%), twins (35%), triplets (55%), and quadruplets (8%). The mean annual increase of weaned young was 3·24 per pair.
The median interbirth interval was 154 days. Of 46 pairs of marmosets, 8 failed to produce young.
Approximately 11% of young born were stillborn and a further 32% of all young born died within 3 weeks; perinatal mortality is largely a result of the failure of parents to rear more than 2 young. In only 2 of 68 triplet births did the parents rear the young unaided.
53% of young born were males but differential mortality reduced the final sex ratio for live young to 50·5% males. Females did not accept and rear the young after caesarian sections.
The linear regression of the growth curve from 5-17 months (where y = weight in grams and x = months) could be expressed as y = 16·6x + 163·6.
The data from 4 marmoset colonies are compared and the relative efficiency of breeding methods discussed.