Saturday, October 08, 2016

Coastal BC Animals: America Bullfrog

American Bullfrog

An American Bullfrog on Powell Lake BC.
Invasive species? Illegal immigrant? Whatever you want to call it, the Bullfrog is not native to British Columbia, and it's not benign. Here in Powell Lake we have the American Bullfrog.

Bullfrogs are native to eastern North America from Canada to Florida. Much like fish farming, Bullfrogs was imported to farm for their meaty legs. From there, they spread throughout the southern mainland and southeast Vancouver Island.


Females are larger than males and can grow to be 20 cm long and 750 grams in weights (8"/1.5 lbs). Males have a large tympanum (ear) behind the eye. Females have a smaller one. This is probably a female.


One way to distinguish a Bullfrog from a Green Frog (also invasive) is the fold of skin over the typanum. A Bullfrog's wraps around the tympanum, but the Green Frog's forms a long skin fold along the back.


Bullfrog tadpoles are large, dark-green, and can grow up to 15 cm long. They can stay in the tadpole stage for up to two years. For this reason, Bullfrogs need to breed in water sources that remain filled all year. Bullfrogs can live up to ten years.



The biggest problem with Bullfrogs is that they take over the territory of native species, often by eating their rivals. They are voracious and will eat anything that will fit in their mouths. That would include the beautiful little Pacific Chorus Frog I saw earlier this summer. Large Bullfrog tadpoles also present a problem, taking food sources away from tadpoles of native frog species.


You can help their further spread. Do not transport either live adults or tadpoles. If you notice a new colony of Bullfrogs developing, contact BC Frogwatch. -- Margy

Reference: B.C. Frogwatch Program (online)

14 comments:

  1. "Voracious" is an understatement - unfortunately there's no way to stop their spread, they've already decimated Cranberry Lake.

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    1. I know they say we should kill the ones we see, but that is so hard. I even hate killing a fish to eat. We usually catch and release, then go to the grocery store. - Margy

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    1. They do get big, but I've seen a garter snake gobble one down for dinner. - Margy

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  3. That is interesting about the bull frogs, hoping there is some way to control the spread of them, but it seems like it is going to be hard.

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    1. Seems to be hopeless. Hopefully they won't spread too far. - Margy

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  4. Hello, wonderful information on the bullfrog. I loved the photos and post. Thank you for linking up and sharing your post. Happy Sunday, enjoy your weekend!

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    1. Thanks for helping us share out posts. - Margy

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  5. Mine co-exist in our frog pond. Only problem, frog pond died. I don't know what happened to the frog tadpoles. We'll see next year. I don't know if they can go into torpor.

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    1. Since our lake doesn't freeze or dry up they only have to find a place to wait out the winter months. Hope you pond rejuvenates in the spring. - Margy

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  6. I've heard about those nasty B.C. Bullfrogs!

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    1. Has your area avoided them? - Margy

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  7. Very informative and great photos. We have only seen small frogs here, cute critters!

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    1. Small frogs are cuter. - Margy

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