What Do Bullfrogs Eat?


What is inside an invasive frog? Bullfrog diet of the Mora River


Bullfrog Diet: Percent of Stomach Contents, 2012


Bullfrogs (Lithobates catesbeianus) are aquatic frogs that live in and near permanent sources of water. An adult bullfrog can weigh as much a 0.5 kg and grow to more than 40 cm in length!
American Bullfrogs
were introduced in northern New Mexico in the 1940s and are now considered an invasive species. In this study, researchers are trying to find out how the presence of bullfrogs impacts native species like the
Northern Leopard Frogs (Lithobates pipiens) are aquatic frogs about 10 cm long and covered with spots.Northern Leopard Frog.
Bullfrogs can have a significant detrimental impact on native species through direct predation, competition for resources, and as reservoirs for disease such as the chytrid fungus.

This study was started in February 2012 when researchers identified two stretches of the Mora River. One is the experimental area where the bullfrogs were eradicated using different methods; the other is the control area where the bullfrog population was left undisturbed. Researchers analyzed the stomach contents of 268 adult bullfrogs found in the experimental area. 


Jesús Rivas, Steven A. Salinas, Micah Daboub, Justin Saíz, Robert E. Ortega, Adrian Carter, New Mexico Highlands University, New Mexico, USA

Rio Mora at Wind River Ranch

Mora River
About the Researchers: 

Students enrolled in Dr. Rivas' Field Biology 494/594 course participated in this on-going bullfrog research. Dr. Jesus Rivas is a biology professor at New Mexico Highlands University. Dr. Rivas is a Venezuelan-born wildlife biologist with an international reputation for his anaconda research that spans 19 years. He founded the Anaconda Project in 1992 and published his doctoral dissertation, The Life History of the Green Anaconda, in 2000. He earned his Ph.D. from the University of Tennessee.


Reading the Graph

1.What makes up the largest percentage of the diet of a bullfrog at Rio Mora?

2. What is surprising about the diet of a bullfrog?

Making Inferences

3. Is there evidence that bullfrogs are cannibalistic?

4. How would you characterize the diet of a bullfrog?

Digging Deeper

5. It is commonly believed that the decline of Leopard Frogs is due, in part, to predation by bullfrogs. Does the data support that idea? Why or why not?

6. Crayfish are not native to the Rio Mora but they are now very abundant. In what way do you think that the bullfrog eradication will impact the Crayfish population?

click here to view the answers.