Managing an Overabundant Koala Population for Conservation of Riparian Habitats on Kangaroo Island, South Australia

The koala population on Kangaroo Island, South Australia has increased from 18 individuals, released in the 1920s for conservation purposes, to an estimated 27,000 in 2001. The selective browsing pressure of koalas on some eucalypt species, particularly rough-barked manna gum, has resulted in significant detrimental impacts to the riparian habitats of the island. In 1997, a management program was initiated to reduce koala densities and restore damaged habitats. Due to the iconic status of koalas, lethal control measures were rejected in favor of a program based on surgical sterilization and translocation. To date, around 6,000 koalas have been sterilized with around 2,700 of those translocated to suitable habitat in the koala’s former range in southeast South Australia. Although criticized as an expensive approach, the Koala Management Program has resulted in reduced population densities and improved tree condition in areas of intensive management. The Koala Management Program has been adaptive to match improved understanding of koala distribution, population size, and ecology on the island. This paper provides an overview of the koala issue on Kangaroo Island, and the management program implemented to restore damaged riparian habitats.