Defined by the authors as animals that have established and spread outside of their native range, many invasive species become economic and ecological burdens. Successful invaders can displace native animals through resource competition, predation or disease-- ushering in biodiversity loss. Globally, invasive species are the second leading cause of animal extinction, preceded only by habitat loss.
Not all introduced animals become invasive. When moved into a foreign environment, many animals find conditions unfavorable and fail to establish. In an effort to gain insight into how frequently introduced animals become invasive, Drs. Jeschke and Strayer analyzed bird, mammal and freshwater fish introductions between Europe and North America. Jeschke comments, "We focused our study on larger vertebrates because there are better historical records about their introductions, which were often done purposefully for human use."
While motivations vary-- some animals make great pets, others have valuable pelts-- humans have been moving animals between Europe and North America for hundreds of years. Enterprising furriers imported American mink into Europe, where the animals escaped from captivity and spread prolifically. European mink have been suffering ever since. Other animals have been introduced unintentionally. Rats were stowaways on the first vessels sailing from Europe to North America. They now flourish in urban and agricultural areas, causing a
Contact: Lori M. Quillen
Institute of Ecosystem Studies