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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  • SalvadoRH-Har
    10/07/2014 - 11:38 a.m.

    When did they start eating anyithing that fits in there moutth.Its pretty cool that they can do that ,but animals can become extinct because of the bull frogs.

    • 21zfmcro
      10/07/2014 - 12:08 p.m.

      all I have to say is that is a lot of bull frogs invading yellow stone national park frogs better hope that they get a lot bigger so they don't eat them

  • AutumnL-Cal
    10/07/2014 - 11:38 a.m.

    Wow, those frogs certainly have an appetite. These frogs have inhabited areas of western montana the 1920's and where probably introduced by farmers so they could sell their legs to be eaten. if i was a farmer and i had those frogs, i would want them to control the pests on my crops.

    • MatthewL-Cal
      10/08/2014 - 06:52 p.m.

      OK, I get what your saying, but what happens when they breed and breed and breed, yeah sounds fun does it not? Good luck with that!

  • JadeT-Cal
    10/07/2014 - 11:44 a.m.

    I can't believe the bullfrogs will eat everything.It's crazy how they will eat each other. I cant believe there a threat. Can they eat dogs.

  • SeanD-Cal
    10/07/2014 - 11:44 a.m.

    These bullfrogs are being bad to the environment. he bullfrogs are killing nature and destroying food. Just put them in a cage with food. 5They're an animal too you know. They may be killing nature, but killing is not a solution. Killing isn wrong, you should round mopst of them up and put them in a good habitat.

  • gesjamie
    10/07/2014 - 11:49 a.m.

    That is cute frog. Is it rile or is it a sculptor of a frog because I did not know a frog could leave its mouth open that long so you could take a picture of it.

  • geskaylee
    10/07/2014 - 11:56 a.m.

    That is crazy, I don't think a frog from around here did that! Well at least I think so. If I see one I wiil capture it and take it as a pet.

  • 21gaware
    10/07/2014 - 12:05 p.m.

    This is a very interesting type of frog, but this frog could cause many problems. One of the problems the frog may cause is eating native frogs. They also spread a fungus that's suspected of causing a widespread decline in amphibians.

  • 21ajmich
    10/07/2014 - 12:06 p.m.

    I myself love to catch frogs, snakes, and turtles. But I did not know that bullfrogs were causing problems. I also did not know that they would eat each other. I hope pretty soon they can control the American bullfrog population.

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