Introduction

Invasive Species Defined

What's Being Done

 National Invasive Species Information Center

Submodule 5: Invasive Animals

Leading Problem Animals

The brown tree snake (Boiga irregularis), a native of Indonesia, Australia, and surrounding areas, has changed the fauna of Guam by eliminating birds, lizards, and small vertebrates. The snake was introduced to Guam between World War II and the mid-1950s, probably as a stowaway on imported cargo. With no natural predators on Guam, the snake quickly became established on the island. In addition, the snake has killed pets and livestock, and is known to inflict painful, mildly venomous bites. It has numerous opportunities to be transported to other Pacific islands since Guam is a shipping hub in the Pacific. Hawaii, being close to Guam, has implemented or is studying many stringent, innovative controls in an effort to keep the snake out of its territory including:

• Funding research to study eradication (such as by trapping and fumigation) and detection methods, and the possibility of biological control by introducing tree snake diseases and parasites
• Educating the public and private sector on the dangers of the snake
• Increasing knowledge of snake biology in hopes of possibly introducing sterility into the invading population

Nutria (Myocastor coypus), a semi-aquatic rodent from South America’ was originally introduced into the U.S. in 1889 for the fur trade. In the 1940s, nutria were released into the wild when the fur market declined. The rodents, found in fresh and salt water, were also intentionally released for weed control. Subsequently, it was noticed that nutria cause serious damage to native vegetation and native wetlands. Now established in roughly 20 states, nutria populations continue to increase because of a high reproductive rate and lack of natural predators. Nutria are known to damage sugar cane, corn, millet, and other crops grown along the Gulf and Atlantic coasts, and to cause a decline in the numbers of native animals. The rodents are also a danger to public safety since they harbor diseases such as tuberculosis and also transmit parasites. Damage from Hurricane Katrina in 2005 is thought to have been compounded by previous coastal destruction by nutria. Control measures include trapping and bounty hunting.

Round gobies (Neogobius melanostomus) are aggressive bottom-dwelling fish that were introduced into the Great Lakes from central Eurasia via ballast water around 1990. Gobies have been able to successfully compete with native bottom-dwelling fish for resources thereby removing these native fish from the food chain. They have also been identified feeding on the eggs of an important food fish, lake trout. A beneficial consequence of goby infestation is that they feed on zebra mussel, a major deleterious invader of the Great Lakes waterway. It is expected that the invasion range of goby will increase since the fish has entered the Mississippi waterway.

Asian clam (Corbicula fluminea), native to SE Asia, has been in North America since the 1920s and is thought to have been imported by Chinese immigrants for food. It is now found throughout the U.S. Due to a high reproductive rate, the Asian clam infests waterways blocking drainage canals and irrigation systems. It alters native invertebrate populations and interferes with nutrient cycles in native habitats.

Cane (or Giant) Toad (Bufo marinus) – Native to tropical America, this toad has invaded parts of Florida and southern Texas. These extremely large toads congregate nightly around homes and other sources of lights to feast on bugs. Cane toads have been intentionally introduced in tropical environs like Hawaii to feed on crop pests. The problem is that they are severely toxic because of chemicals produced in skin glands. Dogs and other animals that bite or simply touch these toads have become ill and even died.

Red-Eared Slider Turtle (Trachemys scripta elegans) – This turtle is native to the Mississippi, Tennessee, and Cumberland Valleys of the U.S. Starting in the 1940s, it is thought that pet enthusiasts released these turtles in the West and Deep South, where they became established. Red-eared slider turtles are highly adaptable and are able to hibernate over the winter to survive in the wild. Because they are aggressive and can be meat-eaters throughout their lives, they have caused imbalances in the ecology of their new habitats. Also, they are able to hybridize with native turtles damaging the integrity of the native species and introducing new pathogens to native animals. Relatively successful attempts to control these turtles include hunting, trapping, and destroying eggs.

Asian Swamp Eel or Rice Eel (Monopterus albus) – The Asian swamp eel, native to eastern and southern Asia, has become established in Hawaii, Georgia, and Florida. It arrived in Hawaii in the early 1900s and on the continental U.S. in the 1990s. It is thought that these eels were introduced as food from Asian immigrants, and as releases from aquariums. Swamp eels are highly adaptable and can breathe in or out of water. They are predators that consume crayfish and tadpoles, therefore leading to a decline in native species. Because they have no known predator in the U.S., their invasive threat is high. Research is underway to determine a method of containment, but with no success to date.