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Alien Encounters is part of the National Amphibian and Reptile Recording Scheme (NARRS)
Coordinated by Amphibian and Reptile Conservation |
North American bullfrog (Lithobates catesbeianus) |
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This is a huge frog which can grow to 15 cm long. It is wary and can be difficult to get a good look at. However, it calls loudly on warm nights during the summer making it easily identifiable - it sounds reminiscent of cattle. Due to the ecological threats posed by this species, its import into the EU has been banned. As such, the chances of finding bullfrogs in the UK are now slim. Nevertheless, a population did go unreported for some years in southern England so it is important to maintain vigilance with regard to this frog. |
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Bullfrog tadpoles (upper right) can spend several years in the water, hence they grow very large, relative to common frog and toad tadpoles (lower left). By the time
they reach metamorphosis, bullfrogs are already almost the size of
an adult common frog.
Bullfrogs
are potentially confused with marsh frogs (also large frogs which
call loudly). However, there are some features that
distinguish the two species. |
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Identification tips |
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(A) When calling, bullfrogs inflate a single vocal sac under the throat rather than the two sacs on either side of the head like the marsh frog. (B) Bullfrogs do not have dorsolateral ridges which are usually prominent in marsh frogs. (C) The calls of the two species are different; bullfrog calls are reminiscent of cattle while marsh frog calls are more likely to be mistaken for waterfowl. |
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Alien Call Sign |
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| Bullfrog | |||
To hear this you may need to click here to install the appropriate plugin. |
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| Information from the GB Non-Native Species Secretariat's Non-Native Species Information Portal. | |||
