Invading bullfrogs will eat almost anything!
Invading bullfrogs will eat almost anything! (Thinkstock / Reuters)
Invading bullfrogs will eat almost anything!
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An invasion of American bullfrogs that will eat just about anything, including each other, is spreading downstream along Montana's Yellowstone River. They pose a potential threat to native frogs, government scientists say.

Bullfrogs were found in surveys along a 66-mile stretch of the river from the Laurel area downstream to Custer, according to U.S. Geological Survey biologist Adam Sepulveda. The number of breeding sites for the frogs almost quadrupled between 2010 and last year, totaling 45.

"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 Sepulveda. He co-authored a study on Yellowstone River bullfrogs appearing in the journal Aquatic Invasions.

Bullfrogs as long as 12 inches when outstretched have been found. One that was caught near the Audubon Conservation Center in Billings last year had a bird in its stomach.

State and federal agencies initially tried to stop the invaders in their tracks by killing them all off. But they gave up after the number of bullfrogs overwhelmed the effort. They're now trying to come up with a strategy to at least contain their spread.

Bullfrogs are native to the eastern U.S. They were spread by humans to every state except North Dakota.

They've caused many problems. The bullfrogs prey on native frogs, out-compete other animals for food, and spread a fungus that's suspected of causing a widespread decline in amphibians, Sepulveda said.

They were first documented in eastern Montana in 1999. Scientists believe they descended from released pet frogs or bullfrog tadpoles used as bait by fishers.

The frogs have inhabited areas of western Montana since the 1920s. They likely were introduced by a farming operation, which sold their legs to be eaten, Sepulveda said.

Critical thinking challenge: Why do invading bullfrogs pose a threat to native frogs?

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  • Jacqueline20023
    10/07/2014 - 12:21 p.m.

    It is amazing what bull frogs can do. They can eat anything that they can fit in their mouth including other frogs! The article says that there are a danger to other native frogs and although people have tried killing them, there are way too many frogs.

  • Sydney7-24-02
    10/07/2014 - 12:21 p.m.

    I can relate to this story because I've been to Yellowstone Natanal Park and know what River they are in. I can also see why they are being a threat to other native animals, because they eat almost everything. I chose this article because I wanted to see if scientists are going to get rid of the killer frogs or keep them.

  • CoUrTnEyCC
    10/07/2014 - 12:27 p.m.

    When the bullfrogs started to grow in population they out numbered the native frogs. They are also eating anything that will fit in their mouths such as birds, or Mosquitos. But with federal agencies killing them to stop the growing of the population they can't be contained. This will hopefully stop when the farming operations seize.

  • jordanr-Orv
    10/07/2014 - 12:27 p.m.

    They should do something, I'm sad to say this but they should make it legal to hunt the bullfrogs not to were they are endangered.

  • Diego2100
    10/07/2014 - 12:54 p.m.

    The invading bullfrogs could extinct the native frog by eating all of them. It says right in the article that these bullfrogs will eat anything that will fit in their mouth. Since its mouth is so wide, it could eat all the native frogs in its path. Scientist are trying to find a way to catch them safley. If the bullfrogs eat all the native frogs before we can catch them, the native frogs will be extinct.

  • cheesedoodle9
    10/07/2014 - 12:54 p.m.

    I think that eventuality if they don't take out the frogs they will kill off 74.3% of all small animals in eastern America.

  • stbernardsam
    10/07/2014 - 12:56 p.m.

    These bullfrogs pose a threat to the native frogs because the bullfrogs are eating anything that fits in their mouths, so to the bullfrogs, the native frogs are food.

  • AngelMcFarland-Pet
    10/07/2014 - 01:01 p.m.

    What my opinion is that I think that they should just make an area where all the bull frogs can stay at so that they wont be in any body way. And also they should have food and water near them so that when they get hungry they can just stay there. What I learned is that bull frogs are very big and that they will eat anything that is in its way that it can fit in its mouth. My connection is that when I was at the beach with my sisters and mom we was swimming and someone had found a frog and it was very big. But someone didn't know that it was a frog and killed it by stepping on it.

  • ma2000dragonball
    10/07/2014 - 01:03 p.m.

    They might pose a threat to native frogs , because bullfrogs act differently then native frogs so therefore the native frogs will be confused and not know what to do with the bullfrogs. The frogs kinds act like humans in a way, like if you might be threatened by someone or something, you'll be afraid

  • robinbra000
    10/07/2014 - 01:03 p.m.

    I have never herd of one frog eating another frog but I guess it could happen if the frog was twelve inches long. I wonder what the biggest frog ever recorded was so we could use it to control the population.

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