Even when habitat is present for native wildlife, animal populations can be seriously impacted, or even eliminated, as a result of the introduction of exotic or non-native species. Exotic plants and animals are mainly introduced in an area by people. For example, about 25 million homes in the US have exotic birds as pets – 85% of which have been imported. Exotic pets are no problem, as long as they remain pets! Its when they escape, become unwanted, or get too big and are dumped in the woods or flushed down the commode that they become a problem!
Most exotic species do not survive in the places in which they have been introduced, but some DO and become a form of “Biological Pollution” mainly impacting native animals by:
- Killing Native Species (some to the point of extinction!):
- Nene Geese and Mongoose
- Brown Tree Snake and Guam Rat
- Sea Lamprey (Great Lakes 1829) wiped out Lake Trout
2. Competing with Native Species for Habitat:
- House Sparrow from England (1853)
- Russian Wild Boar (1912) – Feral hogs compete with deer, turkey, squirrels for mast
- Argentine Fire Ants (1918 from Brazil) destroys native ants, damages crops, found to enhance mortality of quail chicks
- Carp (from Germany 1877) competes with and replaces native fish
- Walking catfish (Florida) destroys bass, bluegill, and other fish
3. Altering the Habitat or Food Web in such a way as to make it difficult for native species to survive
- Opossum shrimp in Flathead Lake, Montana
4. Introducing Disease or Parasites
- Chestnut blight (fungus) from Chinese Chestnuts brought to New York City early in the century – blight killed off American Chestnut
- Dutch Elm Disease (fungus) deadly for American Elm Trees
- Newcastle’s Disease in Parrots – deadly disease to domestic poultry
Here is a classic examples of what can happen with introduced exotic species:
Introduced European Rabbit in Australia
- 24 European rabbits were introduced in Australia in 1859
- In 10 years they numbered in the millions
- Competition with native species resulted in extinctions
- In 1950’s officials introduced a virus that killed off 99% of population; 1% were resistant to virus
- Through Natural Selection this 1% group repopulated the country – now they have 200 million+ rabbits causing an estimated $75 million in damage/year
Heres another example a little closer to home:
- Arrived in 1986 in the Great Lakes
- No known natural enemies and multiply extremely rapidly
- 1990 Lake Erie had densities of 700,000 per square meter
- It cost the Great Lakes basin $500 million/year. How? Clogged pipes!
- They deplete food supply for other aquatic species
- May drive other species of mussels to extinction!
- Have now invaded other rivers, lakes, and streams in other states
What are some exotic species impacting your area? Pythons in Florida have been making the news recently and is a big exotics issue. Do you have kudzu or invasive carp in your waterways? Honeysuckle in your management area? There are things we can all do to combat exotic species from taking over and destroying our native plants and animals.
Take a look in your area and see what doesn’t belong. You may be surprised at what you’ll find!