The American bullfrog is expanding into Yellowstone River in Montana. The invasive species, relatively new to this area, is expanding rapidly, eating everything in its wake, including, sometimes, other bullfrogs.

A new study about the American bullfrog's expansion into the habitat surrounding the Yellowstone River was published this week on October 1 in the journal Aquatic Invasions.

American bullfrogs are an insidious invasive species, found around the world. Bullfrogs spread because humans transported them to other places, often as pets. However, once the bullfrog takes root in another place, it can propagate out of control. These bullfrogs are dangerous to native ecosystems, because they will consume any animal they can swallow, especially other frogs.

"They are going to eat anything they can fit into their mouths. It doesn't matter if it's another frog or a bird or a mosquito," said Adam Sepulveda, a U.S. Geological Survey biologist, who co-authored the study.

American bullfrogs are native to the eastern coast of the US. They are so voracious that they might end up destroying a lot of creatures. Especially at risk is the native Northern leopard frog, Sepulveda said, because there was a great deal of overlap between the leopard frog's habitat and the bullfrog's habitat.

Bullfrogs can take over a natural ecosystem by reducing the natural amphibian population in an area through spread of amphibious disease, and by eating other frogs. The team behind the current study of the Yellowstone River did field studies in three years, 2010, 2012, and 2013, to see how far the frogs had spread and what damage they had done. The team found that the bullfrog is already well rooted in the Yellowstone River area, and can spread further to other nearby areas.

The area that the bullfrog population lived in almost doubled from 2010 to 2013, growing from an area of 37 miles to about 66 miles. This could be a significant threat to biodiversity in the area.

"Bullfrogs were likely introduced to the Yellowstone River region for food, recreational hunting, bait and pest control, and as released pets," said Sepulveda.

The authors of the study suggested educating the public to prevent further introduction of bullfrogs into the area, as well as taking action to remove bullfrogs from land. Officials or land owners need to act quickly to restore the natural ecosystem before permanent damage to biodiversity is done.