The American Bullfrog (Lithobates catesbeianus) is a large amphibian found across North America. Known for its size, this species thrives in various aquatic environments such as ponds, lakes, and slow-moving streams. American Bullfrogs are highly adaptable predators with opportunistic feeding habits, consuming a broad spectrum of prey.
Typical Prey
Adult American Bullfrogs eat a diverse range of prey, focusing on invertebrates and smaller vertebrates. Insects are a substantial part of their diet, including beetles, grasshoppers, crickets, and flies. They also eat spiders, worms, mollusks, and crustaceans like crayfish. Crayfish are a significant food item, often making up a large percentage of their diet, especially for larger individuals.
Beyond invertebrates, bullfrogs frequently prey on smaller vertebrates. This includes small fish, such as goldfish or koi. Other amphibians, including smaller frogs and tadpoles, are common prey. They are generalist carnivores, eating a variety of amphibians. Their diet also includes aquatic eggs of fish, frogs, insects, or salamanders.
Beyond the Usual Diet
Their diet extends far beyond common insects and small aquatic life, highlighting their highly opportunistic predatory nature. These frogs are known to consume almost anything they can fit into their mouths, demonstrating a “eat anything that moves” approach. This can include small mammals such as mice and shrews, and even small birds. Reports also indicate they may prey on snakes, small lizards, and occasionally bats.
Their feeding habits can also include consuming venomous animals, such as certain millipedes and salamanders. Cannibalism is observed in bullfrog populations, particularly in environments with limited resources. They readily prey on smaller bullfrogs. This behavior underscores their role in their ecosystems, especially in areas where they are an invasive species.
How They Hunt
American Bullfrogs use an ambush strategy to capture food. They remain motionless, waiting for prey to come within striking distance. Once prey is close, the bullfrog launches a rapid attack, often leaping short distances. Their powerful, sticky tongue, attached at the front of their mouth, allows them to quickly ensnare prey.
The tongue’s unique saliva can transition between a watery and a thick, sticky texture, enabling it to effectively hold onto captured prey. Bullfrogs swallow prey whole, as they do not chew their food. For larger items, they may use their forelimbs to help stuff the prey into their wide mouths. Their strong jaws and wide gape allow them to consume surprisingly large animals.
Dietary Changes Throughout Life
The diet of American Bullfrogs changes significantly as they mature from tadpoles to adult frogs. Bullfrog tadpoles are primarily herbivorous, feeding on algae, detritus, and various aquatic plant material found in their watery habitats. This plant-based diet supports their growth and development in the initial stages of their life cycle.
As they undergo metamorphosis into froglets and then into adult frogs, their diet gradually shifts from herbivorous to carnivorous. This transition involves a change in their digestive system and feeding mechanisms, allowing them to consume animal prey. The size and type of prey they consume directly correlate with their increasing body size, meaning larger adult bullfrogs can tackle a broader range of larger food items compared to juveniles.