How we know so much about frogs

"The next time you want to release a pet where it doesn't belong, don't."

This is really a story about invasive species. An invasive species is a type of plant, insect, fish, reptile or animal that comes from somewhere else (such as another country) and is brought in to a new area where it overtakes and harms the ecosystem. Invasive species survive because they can live in the ecosystem's climate. Also, they have no predators and usually breed quickly. So their population grows fast and they eat too much of the food that is needed by the other species living there. In some cases, the invasive species can even cause other species to become extinct.

Some invasive species arrive by accident: Tiny bugs can hide in the cracks of people's muddy shoes when they fly home from another country. Water organisms cling to the bottom of ships or survive in the boats' ballast water, moving along with the ships as they travel to new waters where the organisms don't belong. Experts believe that more and more invasive species are arriving in America because people and boats are moving between foreign countries and America more than ever before.

Some invasive species arrive on purpose: people bring exotic birds, animals and snakes home to keep as pets or give as gifts; then the pet gets too big, the person lets the creature out into nature, and suddenly the pet becomes a danger to the ecosystem. For example, in Florida, invasive Burmese pythons are hurting the delicate Florida Everglades ecosystem, gobbling up fish, birds and mammals. This is why there are laws against bringing plants, insects, birds and animals into the country from foreign places. It is also why it is never a good idea to release an animal into the wild when you don't know how it will affect the local environment.

The African-Clawed frog is an example of an invasive species. The African-Clawed frog comes from southern Africa. It has a very big appetite and eats lots of living things, including fish, frogs and insects and the eggs of fish, frogs and turtles. In North America, it doesn't have many predators and can survive in different temperatures. In San Francisco, the frogs have overtaken Golden Gate pond. Scientists are worried they will move on to other water ecosystems and eat up the creatures that live there as well. No one knows how the African-clawed frog got into Golden Gate pond in the first place. Because of the frog's power to destroy delicate pond systems, it is illegal to own the African-Clawed frog in many states.

Here are some other examples of invasive species:

Purple Loosestrife: This plant has invaded North American wetlands. Each plant can produce up to 2.7 million seeds every year. The seeds spread across up to one million acres of wetlands each year. Because local animals do not eat the plant, it keeps spreading and takes over an ecosystem, choking out other plants, which fish, mammals, reptiles and birds need for food.

Zebra mussels: Having arrived accidentally by boat from Asia into the Great Lakes, these mussels attach themselves to hard surfaces, including boat bottoms, and are clogging up pipes, which is causing a problem for people getting water to their houses and buildings. They are also over cleaning the water so that more and more sunlight is getting through to the bottom of the lakes. The result: organisms that depend on darkness to survive are dying off.

The brown tree snake: This snake comes from the South Pacific and Australia. On the island of Guam it has destroyed 10 out of 13 of the native bird species, 6 of 12 native lizard species, and 2 of 3 bat species.

The northern snakehead fish: Originally from China, Russia and Korea, this large fish has begun to invade rivers and lakes in New York State. Hungry and with sharp teeth, this fish eats other fish, frogs, insects and crayfish. It also can breathe out of water, which means it can survive for days out of water as long as conditions are damp. This fish is upsetting the native wildlife populations in New York waters.

The Asian longhorned beetle: Arrived accidentally in cargo from China, this beetle is destroying North American hardwood trees.

Check out these Web sites. (That's how we learned all of this!):