Induced fertility as a wildlife management tool

Abstract

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.

GnRH Single-Injection Immunocontraception of Black-Tailed Deer

“…Since deer do not usually reproduce their first year, have a small number of offspring, and have a life span of 10-12 years, sterilization would be less effective in reducing their population than lethal removal (Dolbeer 1998). Sterilization is best suited for species with a short life span and a high reproductive rate (Dolbeer 1998, Miller andFagerstone 2000). Seagle and Close (1996) used population modeling based on white-tailed deer (Odocoileus virginianus) population estimates to simulate the results of contraception as a management tool.…”

“…Strong site fidelity and smaller home ranges offer greater opportunity for contraception as a management tool for urbanized deer populations, without immigration completely negating the benefits. Sterilization may be most effective to maintain deer herd size after initial herd reduction via another means (Neilson et al 1997, Miller andFagerstone 2000), when a long-term population decline is desirable, or to prevent overabundance in a population.…”

Review of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human‐wildlife conflicts in North America

“…Ornitrol (DiazaCon) is a cholesterol mimic that has a chemical structure similar to cholesterol (Miller & Fagerstone 2000). It inhibits formation of pregnenolone, the parent compound of steroid hormones, preventing formation of testosterone and progesterone.…”

Delivering and registering species-tailored oral antifertility products: a review

“…80224-5 and OvoControl-P), is the only active that confers any targeting as it affects only egg layers (Fagerstone 2002;Yoder et al 2005Yoder et al , 2006. Although effective, their mode of action and pharmacology is dependent on repeated intake of active doses before or during the breeding season (Miller and Fagerstone 2000;Yoder 2000;Fagerstone et al 2008). In this respect DiazaCon and OvoControl use patterns reflect a trade off between achieving efficacy and reducing potential hazards.…”