Protect Our Parks

Invasive American Bullfrog at Home in Yellowstone

A New Three-Year Study

2013 was a good year for the American bullfrog, an invasive species that has established itself in the Yellowstone River floodplain.

A recently released study in the publication “Aquatic Invasions”* indicates the American bullfrog has spread from a 60-kilometer range in 2010 to a 106-kilometer range in 2013 in just this part of Montana. The number of breeding sites over the same time period has increased from 12 to 45. The deep ponds and backwaters of this region are particularly amenable to bullfrog reproduction and maturation, as the frogs use the deep pools for larvae to mature over a cold winter season.

A Threat to Native Frogs and Other Amphibians and Reptiles

The bullfrog’s size (large), eating habits (non-specific), bathroom habits (voluminous), and mobility (high), in addition to being a host for various diseases, has led to their success as an invasive species. The study posits that humans have contributed to the growth in their population by harboring and releasing American bullfrogs for a number of reasons. High water flow in 2011 as well as optimal breeding conditions in the summer of 2012 likely also contributed to the growth in numbers.

As the population continues to grow Yellowstone land management officials will have a challenging task on their hand. A public, popular locale like the Yellowstone River, which is vast and undamned, is a haven for these bullfrogs and there is no easy solution for stopping their spread.

*”Invasion of American bullfrogs along the Yellowstone River”, Adam J. Sepulveda

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