ABSTRACT
Vertebrates have been among the most spectacularly destructive alien species transported by humans, with many species creating huge losses to native species, ecosystems, human health, and economies in the regions to which they've been introduced (Morgan and Woods 1986; Ebenhard 1988; Case and Bolger 1991; Henderson 1992; Pimentel 2002; Pimentel et al. 2000, 2005; Blackburn et al. 2004; Jenkins et al. 2007; Kroeger 2007). Progress has been made in recent years toward reversing some of these impacts by removing certain of these species from some invaded regions (e.g., Nogales et al. 2004; Campbell and Donlan 2005; Clout and Russell 2006; Howald et al. 2007). In most instances, however, perpetual control of widespread or abundant alien vertebrates is required to minimize damage to especially important areas or resources. However, such eradication and control operations are achieved at high cost and can only be successful in limited circumstances, making them an unreliable foundation upon which to base a nation's ecological future. A much more efficient and cost-effective means of managing alien species is to prevent their introduction in the first place. This remains an important goal in alien-vertebrate management because the majority of the world's vertebrate fauna has not yet been introduced everywhere, and most invaded regions are still afflicted by only a relatively few species. Furthermore, prevention is far more cost-effective than post hoc response (Naylor 2000; Touza et al. 2007). Consequently, prevention of future invasions should form the centerpiece of any region's alien species management program.
