COMPUTER-SIMULATION OF VASECTOMY FOR WOLF CONTROL

Recovering gray wolf (Canis lupus) populations in the Lake Superior re gion of the United States are prompting state management agencies to c onsider strategies to control population growth. In addition to wolf r emoval, vasectomy has been proposed. To predict the population effects of different sterilization and removal strategies, we developed a sim ulation model of wolf dynamics using simple rules for demography and d ispersal. Simulations suggested that the effects of vasectomy and remo val in a disjunct population depend largely on the degree of annual im migration. With low immigration, periodic sterilization reduced pup pr oduction and resulted in lower rates of territory recolonization. Cons equently, average pack size, number of packs, and population size were significantly less than those for an untreated population. Periodical ly removing a proportion of the population produced roughly the same t rends as did sterilization; however, more than twice as many wolves ha d to be removed than sterilized. With high immigration, periodic steri lization reduced pup production bid not territory recolonization and p roduced only moderate reductions in population size relative to an unt reated population. Similar reductions in population size were obtained by periodically removing large numbers of wolves. Our analysis does n ot address the possible effects of vasectomy on larger wolf population s, but it suggests that the subject should be considered through model ing or field testing.