Invading bullfrogs will eat almost anything!
American bullfrogs that will eat just about anything, including each other, are spreading. Their numbers are growing along Montana's Yellowstone River. They pose a potential threat to other types of frogs, scientists say.
Bullfrogs were found along a 66-mile stretch of the river. That's according to U.S. Geological Survey biologist Adam Sepulveda. The breeding sites for the frogs are expanding quickly.
"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 was involved in a study on Yellowstone River bullfrogs. The study appears in the journal Aquatic Invasions.
Bullfrogs as long as 12 inches when outstretched have been found. One that was caught near Billings last year had a bird in its stomach.
State and federal agencies initially tried to stop the invaders. They planned to kill them. But they gave up. There were simply too many bullfrogs. Now officials want to just contain the frogs.
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 frogs prey on other, native frogs. They take food from other animals. And they spread a fungus. The fungus can harm other amphibians.
The bullfrogs were first documented in eastern Montana in 1999. Scientists believe they descended from released pet frogs. Or they came from bullfrog tadpoles that were used as bait by fishers.
The frogs have lived in western Montana since the 1920s. They likely were introduced by a farming operation. It sold the frogs' legs to be eaten, Sepulveda said.