ANNUAL REPORT 2006 - Denver Zoo

Birth Control in ZooMammalsLynn W. Kramer, D.V.M.Vice President for Biological ProgramContraception is the deliberateprevention of pregnancy in mammals.Why do we need to control breedingin zoos? Today, accredited zoos areat their carrying capacity for manyspecies and most holding spaces arefilled. Animal collections are nowcarefully planned and managed toensure that populations do not exceedtheir available space. Consequently,cooperative breeding programs havebeen instituted to maintain geneticallyhealthy populations of zoo mammals.Denver Zoo utilizes a variety ofcontraceptive methods to manage ourmammal collection. The simplest isto just keep males and females apart.We also use permanent contraceptivemethods that require surgery such asvasectomies, spaying and castrations.The most innovative techniquesinvolve hormonal therapies thatprevent ovulation and are reversible.The most commonly used hormonaltherapy involves a drug that is in asterile implant for female mammals.The implant is surgically insertedunder the skin between the shoulderblades where animals cannot removethem. A new implant is inserted everytwo years. These implants offer areversible form of contraception. Whenwe want to resume reproduction ofa certain species we can remove theimplant and most females begin tocycle in about six months.This drug is also available in a liquidform and in grain impregnated with thedrug, thereby allowing us to deliver thecontraceptive orally on a daily basis.There was an industry-wide needto coordinate the use of the variouscontraceptives in zoo animals. In 1999,the Association of Zoos and Aquariumsestablished the Wildlife ContraceptionCenter (WCC) at the St. Louis Zoo.The WCC maintains a databasethat monitors all contraceptives inall mammalian species. You can beassured that Denver Zoo’s team ofanimal managers and veterinarians arechoosing and administering the mostappropriate contraceptive methodsavailable.19