U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

July 2006


Invasive predators have had devastating effects on species around the world and their effects are increasing. Successful invasive predators typically have a high reproductive rate, short generation times, a generalized diet, and are small or secretive. However, the probability of a successful invasion is also dependent on the qualities of the ecosystem invaded. Ecosystems with a limited assemblage of native species are the most susceptible to invasion provided that habitat and climate are favorable. In addition, the number of invasion opportunities for a species increases the likelihood that the species will successfully establish. The list of routes of entry or pathways into many ecosystems continues to grow as transportation of goods into even the remotest areas become common. Species may enter new areas accidentally (e.g., hitchhikers on products) or as intentional introductions (e.g., sport fish). Pet releases, either accidental or intentional, are a growing area of concern as exotic pets become common and the desire for new or different species grows. Several invasive predators have had major effects on prey populations around the world (e.g., black rats, feral cats, mongoose) or have had devastating effects in isolated areas (e.g., brown treesnakes, Nile perch). Although management of established species has been a priority, eradication has been extremely difficult once a species has become widely distributed. However, little resources are directed toward interdiction efforts, removing incipient populations, or preventing new introductions. The regulation of animal movement in most countries and the inspection of products being moved were not developed to protect native ecosystems. Thus, species may be moved with relative ease between regions and countries. The most cost effective approach to invasive species management is to prevent new species from becoming established by providing funding for interdiction efforts, research prior to a species becoming widespread, and restricting the movement of species.