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 and poses 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, rising to 45 total.

"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, who 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 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., but are known to have been spread by humans to every state except North Dakota.

They've caused problems elsewhere by preying on native frogs, out-competing other animals for food, and spreading a fungus that's suspected as a cause of 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, likely from a farming operation that 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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  • TR2001golden
    10/17/2014 - 01:02 p.m.

    It is crazy that a bullfrog can eat almost anything. If they can eat anything what is their favorite food? Who knows. Maybe we will never find out their favorite food. Oh well.

  • joshn-Koc
    10/18/2014 - 07:32 p.m.

    Invading bullfrogs pose a threat to native frogs because they eat anything. They even eat their own species. Native frogs are in danger because of cannibalism. As their numbers increase, the threat to other frogs increase as well.

  • KiaraMc-Wil
    10/19/2014 - 01:41 p.m.

    Although they have yet to hurt us as humans, in the animal kingdom, these guys could become a major issue. Once the frogs out-do the inferior species, the food chain could be totally different.Affecting the way animals in Montana live.

    10/23/2014 - 02:22 p.m.

    The invading bullfrogs pose a threat to native frogs because they are eating the native frogs. They are causing native frogs to go extinct by making them their prey.

  • MadisonSch
    10/26/2014 - 08:42 p.m.

    This would be a really cool pet to have one day. Just think, you do not have to spend a lot of money on pet food when you can give it your left overs.

  • Hallie_halpal
    11/05/2014 - 09:45 p.m.

    Well I have a few things on my mind about this topic. Such as maybe their just all hungry, not enough food. Maybe because they were made to do that, eat birds and eachother. The frogs are like cannibals. We shouldnt kill them off though just because they eat eachother and other frogs doesnt mean we need to kill them all. We, humans, sometimes have cannibals we generally kill them off or prison them but dont kill everyone. Right?

  • kenneth.holmes08
    2/03/2015 - 01:11 p.m.

    This is crazy! This article sounds like a horror movie preview. I had a pet bullfrog and I named him Jeffery. I fed him frogs from my creek because bullfrogs eat anything they can fit in their mouth.

  • kizariah-Che
    2/09/2015 - 11:54 a.m.

    Bullfrogs pose a threat to native frogs because the bullfrogs could possibly eat them and the native frogs might become extinct. I think bullfrogs should be contained and secured because I don't know what else they'll eat. the article did say that they eat anything that fits in their mouth

  • briannac-DiB
    3/01/2015 - 01:25 p.m.

    Bullfrog are pretty awesome of they can eat almost any think they want and it no be a problem for them. I really injoy learning about frogs. I love frogs so in makes me happy to see all the different types and what there do and eat.

  • Haley Patterson
    3/30/2015 - 01:51 p.m.

    This would be a really cool pet to have one day. Just think, you do not have to spend a lot of money on pet food when you can give it your left overs.

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