Bullfrog (Rana catesbeiana)

Description: The bullfrog is the largest of all North American anurans. Adults may reach a length of 20 cm (7.9") from tip of nose to vent. The dorsum of adults is generally uniform in color, ranging from light green or olive to a very dark green or brown. Individual color is variable since very dark individuals taken from deep, dark waters will lighten in color when removed to brighter, sunlit situations. The venter is usually a pearly or creamy white. Faint, darker spotting or mottling may be present on either the dorsum or venter. The throat of males is pale to bright yellow; in females, the throat is the same color as the rest of the venter. Also, the male's tympanum is obviously larger than the eye diameter; in females, the tympanum is equal to eye diameter.

The dorso-lateral fold is nearly absent except for a short fold beginning just behind the eye and curving down immediately behind the tympanum. The absence of a dorso-lateral fold serves to separate bullfrogs from green frogs, a similar species that overlaps the bullfrog in size. Mink frogs sometimes lack a dorso-lateral fold and could be confused with a small bullfrog. Other distinctive features, notably the musky odor and more boreal habits of the mink frog, can be used to separate the two species.

Bullfrog tadpoles are light to dark, mottled green or brown dorsally, with a bronze iridescence on the venter and sometimes extending to the sides. Their tails have black spots, some round and some dumbbell shaped. First season larvae measure 3-3.5 cm (1.2-1.4"); second season larvae (1 year after egg laying) measure 7.5-9 cm (3.0-3.5"); and third season larvae (2 years after egg laying) measure 10-14.5 cm (3.9-5.7").Third season larvae show well-developed hind legs prior to actual transformation.

Voice: The bullfrog's celebrated call is a low, resonant "rum" that carries far across the water and characterizes a summer evening almost as well as the spring peeper's peeping typifies a spring night. They also utter a stuttered series of "rum-rum-rum."

Audio: Bullfrog call (coming soon)