An evaluation of the suitability of contraceptive methods in golden-headed lion tamarins ( Leontopithecus chrysomelas ), with emphasis on Melengestrol acetate (MGA) implants: (I) effectiveness, reversibility and medical side-effects

Finding a responsible method of population control that does not compromise animal welfare is a pressing problem for zoological institutions and conservation breeding programmes. This is exemplified by the conservation breeding programme of the golden-headed lion tamarin. The number of golden-headed lion tamarins in captivity is currently being limited by, among other means, the use of contraception. In a study on the effects of contraceptive methods used in golden-headed lion tamarins, data were collected through the distribution of a survey. The use of melengestrol acetate (MGA) implants in females was by far the most widespread contraceptive method. It was very effective in preventing reproduction, provided that females were not pregnant at the time of implantation. Pregnancies that had commenced before MGA implantation were carried to term and resulted in viable infants, as far as noted. However, the degree of reversibility was very low and, if females did conceive after MGA implantation, infant survival was lower than expected. The widespread use of MGA implants in golden-headed lion tamarins (and probably other species) should be seriously reconsidered. Alternative methods of population control should be investigated. Possible options include the use of other contraceptive methods, limiting the number of offspring through natural factors and the use of euthanasia under very strict conditions. Animal welfare implications associated with the use of euthanasia are discussed.