Egg fertility among vasectomized and non-vasectomized male resident Canada geese at the Wildlife Conservation Park/Bronx Zoo

Abstract

In 1991, a vasectomy program was initiated at the Wildlife Conservation Park/Bronx Zoo to minimize the population growth of resident Canada geese (Branta canadensis). Sixty-nine males were vasectomized over a 6-year period. From 1994 to 1998, egg fertility was examined in females paired with vasectomized and non-vasectomized geese. Of the 340 eggs laid by females paired with vasectomized males, 12% were fertile. In comparsion, of the 526 eggs laid by females paired with non-vasectomized males, 90% were fertile. The vasectomy procedure was easier to perform on males captured during the breeding season than on those captured during molt owing to the enlarged size of the vas deferens. Where resident Canada goose populations are small and resources available, the implementation of a vasectomy program can be effective in reducing population growth. Zoo Biol 19:35–40, 2000. © 2000 Wiley-Liss, Inc.