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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  • jordanm-tri
    10/09/2014 - 03:11 p.m.

    bullfrogs are invading decause they are ateing frogs and bsird or mosquito if they strat ate more they going to make more bullfrogs they will make moren grops and take over

  • kiac-tri
    10/09/2014 - 03:14 p.m.

    bullfrogs pose a threat to native frogs because the bullfrogs eat almost anything also other bullfrogs,also bullfrogs were found in surveys along a 66 mile stretch of the river

  • marangeler-tri
    10/09/2014 - 03:14 p.m.

    bull frogs pose a threat to native frogs because the bull frogs species are dieing thats why the bull frog is posing a threat to the native frog also the frogs inhabited to western montana since 1920s thats why the bull frogs are posing a threat to native frogs.

  • ksadat-5
    10/09/2014 - 07:21 p.m.

    This is very interesting! American Bullfrogs are a threat to native species of animals in all states excluding North Dakota. These frogs will eat anything they find to the point where they will actually eaten their own kind. These American Bullfrogs pose a threat to other native species of animals because if the Bullfrogs eat the prey, there will be no food left for the predators. This will cause other species to slowly die out.

    I can not believe that American Bullfrogs will eat anything they can. This is very weird that they would actually eat another frog! It is disgusting that they found an actual bird in ones stomach! When I hear the word "Bullfrog," I usually never give it a second thought. But now, I will.

  • NikkiS-5
    10/09/2014 - 07:29 p.m.

    The invasion of the Bullfrogs has begun. Along the Yellow Stone River, Bullfrogs are spreading like wild fire. They will eat anything that fits into their mouths; including, birds, bugs, and fellow frogs. Bullfrogs may grow up to twelve inches long. Many state agencies have tried to stop the spread of these amphibians because local species are being out run. These attempts failed. I believe these bullfrogs should be relocated. If they are not, many local amphibians will start to vanish due to the amount of food, shelter, anf fungus being spread by these weird creatures.

  • BeckettN-2
    10/09/2014 - 09:12 p.m.

    This article is about bullfrogs who have been breeding out of control and eating everything in their way, including birds and other frogs. Federal Agents have tried to stop them by killing them off, yet some still survived and overran their efforts. The Agents are now trying to contain their spread. I think that the advancement of frogs could endanger species already close to extinction.

  • addyl-Bla
    10/09/2014 - 09:19 p.m.

    This story is called invading bullfrogs will eat almost anything. Did you know that bullfrogs eat anything that they can fit in to there mouth they will even eat other frogs that is weared right and bullfrog carry a bad disye that is bad if they tech you. The scientists are trying to kill the bullfrogs but that did not work so they now are trying a know plain and studying them.

  • DylanT-5
    10/09/2014 - 10:14 p.m.

    American bullfrogs will eat practically anything they can fit into their mouths, including themselves. Tons of bullfrogs are spreading downstream Yellowstone River in Montana. Native frogs there are threatened by these bullfrogs, according to scientists. Bullfrogs can eat things ranging from a mosquito to a bird. Bullfrogs can outstretch up to a massive twelve inches. In 2006, a bullfrog was caught with a bird in its stomach. Federal agencies tried to stop the invasion by hunting down bullfrogs and killing them off, but their numbers increase too drastically. They are now trying to come up with a strategy to contain the spreading of bullfrogs.

    I think bullfrogs pose a major threat to farmers, small-pet owners, and wildlife. If they can fit things up to twelve inches in their mouths, they can probably eat medium sized birds or even a small squirrel. The fact that they are breeding and spreading rapidly is a huge problem. It is critical to stop the spreading of bullfrogs.

  • HenryS-3
    10/09/2014 - 11:54 p.m.

    This article is about an invasion of American bullfrogs in the U.S. They will eat just about anything, including each other, and are in every state except North Dakota. I like all animals, but then again, not all animals eat each other. Come on, 12 in., that's truly scary! I hope I never have to encounter one.

  • JesseE-2
    10/09/2014 - 11:59 p.m.

    American bullfrogs are currently spreading their rapidly increasing population along the Yellowstone River in Montana. The American bullfrog is an invasive species that has populated western Montana since at least 1920s and has been spread to almost every state in the U.S., naturally and by humans. The bullfrogs will supposedly consume any animal within reason and size constraints. Because of this, the bullfrogs now pose a threat to the ecosystem of Yellowstone River, as they could supposedly out-compete other animals for food, prey on various local animals, and spread a fungus that is possibly dangerous to other amphibians.

    I found this article to be enticing in that it provided readers knowledge of a natural phenomenon that is not usually explored or discussed in news media. The structure was also clean, albeit slightly abnormal, and the writing style was highly informative and clear.

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