Proceedings of the Vertebrate Pest Conference

A growing interest in nonlethal methods for population control of nuisance or damaging species of wildlife has fostered research in reducing fertility of these overabundant wildlife species. Fertility may be reduced by interfering with the fertilization of the egg (contraception) or interfering with the implantation or development of the fertilized egg (contragestion). Research using injectable porcine zona pellucida (PZP) and gonadotropin releasing hormone (GnRH) vaccines has demonstrated that several mammalian species can be contracepted, reducing fertility for several years without revaccination. However, because vaccines currently require delivery by syringe or bio-bullet, there is a need for infertility agents that can be delivered orally. Researchers are therefore considering materials that have resulted in reduced reproductive rates in the agricultural industry. Because of the cost of getting new technology approved by the FDA, materials already approved for other purposes that can be redirected for use in wildlife infertility may have a better chance of getting approved as wildlife infertility agents. Two compounds used in the broiler chicken industry have been found to reduce hatchability if given to the layer. Due to the rapid increase of Canada geese in our parks, research is ongoing with these two compounds to reduce hatchability in the Canada goose egg. Research is also underway to test a cholesterol mimic that competes with cholesterol as the parent compound for steroid synthesis. This compound could reduce fertility in both mammalian and avian species and is currently being tested in rodents. Natural plant materials such as phytoestrogens and ergot derivatives that result in reproductive losses in domestic animals should be also explored as reproductive inhibitors in overabundant species of wildlife.