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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COMMENTS (30)
  • tyreasewb4
    10/09/2014 - 02:13 p.m.

    no that do not eat nunthing they eat flys and all kinds of insexs like flys and evey things like that and i like tthis one was the best one i did to day

  • marvellh-Orv
    10/09/2014 - 08:11 p.m.

    It's pretty crazy how these frogs are eating anything in there way it's pretty crazy but at the same time it's cool.Because i have never heard of a frog that eats everything that it can fit in it's mouth.

  • BrandonT-4
    10/09/2014 - 08:23 p.m.

    In the yellow stone river bullfrogs will eat pretty much anything, even themselves. They are starting to take over and need to be tamed. I also think that they should decrease them because they will eventually die out cause of not enough resources.

    I think this is a serious problem that needs to be fixed soon. If not their should be bullfrog hunting season.

  • Damikus123
    10/13/2014 - 12:55 p.m.

    From point of view i thought frogs are vegiterians, also i thought they only ear insects. Even though this is a type of frog doesnt mean they eat what regular frogs eat , they don't have the size for nothing. American Bullfrogs have been exposed that they will even eat each.

  • 22103
    10/14/2014 - 01:20 p.m.

    There is an invasion of bull frogs going on in Montana. One good thing about this is that there are more of the little froggies than ever. However, a bad thing about this is that the bullfrogs are eating other frogs and scaring them off. One thing that i find interesting is that scientists are capable of tracking that many organisms. In short bull frogs are invading a non indigenous area and getting rid of the rest of the frogs.

  • TaylorHartman-Ste
    10/14/2014 - 01:21 p.m.

    I am personally not a huge fan of any type of frogs whatsoever, so this article really grosses me out. I think that they are dirty, loud creatures.

  • r2000soccer
    10/16/2014 - 08:41 a.m.

    bullfrogs pose a threat to native frogs by preying them competing other animals for food, and spreading a fungus that's suspected as a cause of a widespread decline in amphibians.

  • ws2001wrex
    10/16/2014 - 01:02 p.m.

    The invading bullfrogs pose as a threat because, the Bullfrogs are willing to eat anything and or everything. Which can could be food that other frogs eat and or the other frogs themselves. So, these pose a threat to those frogs for these reasons.

  • martinshark3
    10/16/2014 - 02:40 p.m.

    That is so cool that bullfrogs can eat birds. But what I do wonder is how does it manage to fit a bird in it's mouth?

  • devonm-3
    10/17/2014 - 01:10 a.m.

    Bull frogs are taking over Montanias Yellow stone river and eat everything. Birds, mosquitoes, and even other frogs are being eatin by this extreme frog. These frogs are pretty large some up to a foot long. With their massive size it allowes them to eats massive creatures, like an entire bird. The population is getting to large and the Bull frogs are going away from the river to more civilized areas now. The frogs spread fungus and are knocking down many other speices numbers by how much food they consume. These frogs are crazy they eat everything and are very large . I would love to see one in real life but not have them in Hermosa Beach they would take over the green belt. These frogs seem to be harmless as long as they stay out of civilization and in their swamp.

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