It's a frog eat frog world!


     Why are frogs so happy?
(see bottom of page for answer!)

Picture a garbage disposal.  Got it?  Well, that pretty much sums up the American Bullfrog.  This species of frog is known for eating practically anything that moves in front of it.  They are mostly carnivorous nocturnal feeders that love to eat invertebrates and vertebrates alike.  Some of their favorites include: house mice (Mus musculus), garter snakes, small birds, and even their fellow frogs! Yes, they actually can be cannibalistic. Bullfrogs also play a very important part in keeping the insect population down, like mosquitoes.  The only thing adult bullfrogs will not eat is the algae that their young tadpoles enjoy.

Image of Rana catesbeiana (North American bullfrog), credit to David Blank

Being one of the more dominant predators in its environment, bullfrogs will usually partake in a "sit-and-wait" way of feeding.  Adults tend to sit quietly on their lily pads until some sort of prey comes by.  When close enough, the bullfrog will use its legs to hop on its dinner, wrestle with it if needed, and use its extraordinarily strong tongue to keep it down.  Once they have full control, they start enjoying their meal.

Digestion for the bullfrog, begins in its mouth.  Then the food will pass through the esophagus into the stomach of the frog.  Here digestive enzymes will start to breakdown food molecules.  Traveling next through the small intestine, most of the actual digestion will take place here.  The nutrients are absorbed in the intestine and waste products are passed through cloaca vent for excretion.

Amphibians in general, have a double circulatory system.  The bullfrog is no exception.  It has a heart with three chambers, consisting of one ventricle and two atria.  The oxygenated blood is pumped from the left atrium into the rest of the body, while poorly oxygenated blood is pumped from the right atrium into the lungs.  When in the water, the bullfrog can stop the circulation of blood into the lungs, but continues the circulation of blood within the skin.  Since frogs can breathe partially via their skin, this enables the frog to continue breathing underwater without the aid of gills.

Image of Amphibian Circulatory System, credit to


Answer: Because they eat whatever bugs them!

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