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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COMMENTS (293)
  • 21amtrud
    10/07/2014 - 12:07 p.m.

    This article was very cool to read! Bullfrogs are causing so many problems in lots of states. Bullfrogs will fit anything in their mouth! Bullfrogs as long as 12 inches or a foot long has been found in some states!

  • wirzbcla000
    10/07/2014 - 12:09 p.m.

    That's so weird they ate bird, that's kind of sad. I wonder if theirs a way to contain them but not put them in extinction. They pose a threat to native frogs to because if they will eat other frogs, anything they can put in their mouth. Its a really bad thing that should be fixed.

  • k02snappy
    10/07/2014 - 12:11 p.m.

    That is a lot of bullfrogs! They need to do something fast of the bullfrogs will kill off all the other frogs and birds. those frogs must be huge to eat a bird!

  • Wikipedia84
    10/07/2014 - 12:18 p.m.

    I'd like to see one of these close up, just to see how big their mouth is. I can't believe it ate a bird though, but, that leaves me to wonder.. How did it ever catch a bird...

  • Adi5667
    10/07/2014 - 12:18 p.m.

    I find this article interesting because this is a non-manmade catastrophy that could posssible destroy the entire Yelllowstone environment. It is also amazing that this bullfrog will eat anything from a bird to another frog.

  • Adi5667
    10/07/2014 - 12:18 p.m.

    I find this article interesting because this is a non-manmade catastrophy that could posssible destroy the entire Yelllowstone environment. It is also amazing that this bullfrog will eat anything from a bird to another frog.

  • Annapie3
    10/07/2014 - 12:19 p.m.

    This article is really interesting because this was the first time I saw an article about frogs eating everything including each other. I think this is really odd and is this cannibalism for frogs? This article is so weird I think it is fake. For example: '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.'

  • Morgan_Br0
    10/07/2014 - 12:19 p.m.

    The invading bullfrogs pose as a threat to the native frogs because the bullfrogs will eat anything that can fit in their mouth and the native frogs are food to the bull frogs.

  • LucaL123
    10/07/2014 - 12:19 p.m.

    Wow it's crazy how bull frogs can eat anything! If the government doesn't do anything the whole frog population could go extinct, the entire food chain will soon be falling apart. Hope the crises will soon be resolved.

  • aija
    10/07/2014 - 12:20 p.m.

    I think that it is very interesting that there are bull frogs that eat anything. Well, anything that they can fit in their mouths. I am surprised that they have been settling in the eastern U.S.. The article says that they have been spread by humans except to North Dakota. The article says that they prey on other frogs too, that's messed up.

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