Bullfrog (Rana catesbeiana) 



Description: The largest of North American frogs, adult Bullfrogs may reach 8 inches in body 

 length. The skin is smooth. Adults are usually pale to dark green or brownish green with 

 darker spots or blotches. There are a series of black bands across the legs. The underside is 

 cream to yellowish with gray mottling. No dorso-lateral folds are present, however there is a 

 prominent ridge running from the eye over the tympanum to the shoulder. Males have 

 extensive yellow pigment on the underside, especially in the throat region, and swollen 

 thumbs. The diameter of the tympanum is larger than the diameter of the eye in males but 

 about the same size in females. 



Eggs and Tadpoles: Egg masses are a 1-2 egg thick film of thousands of eggs and may reach 

 several feet across. Tadpoles may reach 4.5" in total length and are olive green with 

 numerous black spots dorsally; the belly is white to creamy with varying amounts of dark 

 mottling. 



Similar species: Other Montana Ranid frogs have dorso-lateral folds. 



Habitat and Habits: Bullfrogs are rareK' seen far from the water's edge and are usually in the 

 water. They are associated with larger bodies of quiet water such as ponds, lakes or 

 backwaters of streams, usually with extensive emergent vegetation such as cattails or reeds. 

 They emerge in the spring only after air and water temperatures have warmed considerably 

 and insect populations are beginning to proliferate. Breeding takes place in June when males 

 attract females to their territory by a series of very deep, loud "brr-umps." The large mass of 

 eggs tend to float on the surface when first laid, but sink into the water prior to hatching 

 (Hammerson 1982a, Nussbaum et al. 1983). Tadpoles over-winter in the Pacific Northwest, 

 transforming during their second summer (Nussbaum et al. 1983, Leonard et al. 1993). The 

 bullfrog is a voracious feeder, eating anything smaller than itself, including ducklings, fish, 

 mice, frogs, and small turtles. Bullfrogs have been implicated in extirpations of native ft"ogs 

 and turtles, and declines in waterfowl production (Hammerson 1982b, Leonard et al. 1993). 



Surveying: Both tadpoles and adults can be easily detected visually or sampled by using a 



dipnet; both may be found from spring through fall. Capture success of adults is enhanced by 

 night sampling using a headlamp, as they are very war>' and do not allow close approach 

 during the day. Eggs are also easy to detect when laid in the early summer. 



Status: Bullfrogs are native to the eastern and central U.S. and have been introduced to the 

 western states. There are two historic records from 1970 in the Long Pines (Appendix 4). 

 They were introduced into western Montana prior to the 1 960's, but the date when they were 

 first brought to southeastern Montana is unknown. Bullfrogs were not recorded on our 

 surveys; however, the specific sites of the 1970 collections were not re-surveyed. They 

 should be watched for in ponds, lakes, or slow streams on the Sioux-CNF. Any located on 

 the Sioux-CNF should be well-documented. 



Montana Natural Heritage Program rank: G5 SE4 



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