Invasive is a term used when the exotics become so successful they harm the environment, human health and/or the economy. In Louisiana, for example, millions of nutria, a semi-aquatic rodent native to Argentina, damage thousands of acres of wetlands each year.
In Illinois, Asian carp have invaded the state's rivers. Known as the big fish that jumps into boats and sometimes strikes boaters, these carp now make up more than 60 percent of the fish biomass in the Illinois River. Population surveys have found that as many as 2,800 can live in each mile of some rivers.
Perhaps the worst examples of invasive, exotic species are the rats that reached oceanic islands on shipwrecks. About half of the many extinctions of birds and reptiles on ocean islands are attributable to rats.
But wildlife need not be exotic to be invasive. Even native species can become pests. Too many white-tailed deer destroy forest ground cover and sapling trees. They kill about 200 people annually in deer-vehicle collisions. And insurance companies expect about 1.5 million deer-vehicle collisions annually that cost more than a billion dollars in claims. And let's not forget Canada geese. They damage vegetation in parks and on golf courses, and when struck in flight, they can take down airliners.
Even bullfrogs, native to eastern and central U.S. states, wreak ecological havoc. They have been introduced throughout the West, presumably to harvest them for their tasty legs. But they are ravenous predators that eat anything they can swallow -- turtles, snakes, birds, other frogs and even recently hatched alligators. In Arizona, bullfrogs eat the federally threatened Chiricahua leopard frog.
Like it or not, wildlife affects us all. And often its negative effects can be attributed to invasive, exotic species.
Send questions and comments to Dr. Scott Shalaway, 2222 Fish Ridge Road, Cameron, WV 26033 or by email at sshala...@aol.com.