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An analysis of the stomach contents of thousands of American bullfrogs


Baby painted turtles found in the stomachs of bullfrogs. New research shows invasive American bullfrogs will eat birds, shrews, baby turtles, and their own species. (Credit: Stan A. Orchard)


An analysis of the stomach contents of thousands of American bullfrogs on Vancouver Island shows that the invasive pests are prone to eating just about anything -- including songbirds, baby painted turtles, and juveniles of its own species.

The American bullfrog is native to eastern North America, but has spread to other parts of the continent pet owners and recreational fishermen, among others. Their lack of predators and robust appetite and breeding patterns allow the species to spread wildly.

Out of 18,814 identifiable remains in the stomachs, there were 15 different classes of animals identified. It probably won't come as a surprise that insects, particularly wasps, dragonflies, and damselflies were the most common class of creatures the bullfrogs consumed.

But the study also found 24 shrews, 16 voles, and nine Coho salmon during the investigation.

Several had consumed baby painted western turtles, which are endangered on Vancouver Island.

One bullfrog had four adult Pacific treefrogs in its stomach. Another had eaten a songbird whole. 

There were 51 instances of cannibalism of baby American bullfrogs.

These results, the authors say, reiterates the widespread opinion that invasive American bullfrogs are causing ecological harm to their adopted habitats.

The work was funded by the Capital Regional District Departments of Water and Parks in Victoria and the municipalities of Langford, Metchosin, and Highlands. It was published in the open-source journal NeoBiota.

Kate Allen is the Star's science and technology reporter. Find her on Twitter at @katecallen.




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