Monday, July 7, 2008

About Bullfrogs

We have a small pond put in for the purpose of attracting frogs. Since it's not very large, we've had mostly Green Frogs in residence with other toads and frogs using it for mating. Back in Alabama we had a bit larger pond and did attract a bullfrog for a few years. They take dominance over a pond, so we didn't see much else those years.

The Bullfrog (Rana catesbeiana) is the largest Virginia native frog measuring from 3-1/3 inches to almost 8 inches long not including the legs which can be from 7-10 inches long. They are also the largest frog in North America. They are a drab brownish-green color on top with a yellowish white coloring below. The large circles behind the eyes are their eardrums with the females being about the size of the eye and males being considerably larger than the eye.

Territories are emphatically established with calls, postures, chasing, jumping and fighting if necessary. Their distinctive call is said to sound like a distant roar or bellow of a bull.

Bullfrogs will eat almost anything living that it can at least partially swallow. They are voracious predators, feeding on any small animal they can catch, including big and small insects, crayfish, other frogs and bullfrogs, fish, worms, turtles and even small snakes.

There are records of bullfrogs feeding on birds and baby alligators. They have teeth on the roof of their mouth and a tongue capable of flipping prey into their mouth. Bullfrogs can leap up to 6 feet in distance. They help to keep down mosquito populations but they can also have a negative effect on other species of frogs since they don't really have any natural predators.

They can secrete nasty toxic substances from their poison glands (called paratoid glands) that can poison a dog if it tries to eat one. (NOTE:  Read comments below article relating to this statement.)

This frog species prefers larger bodies of water, but will take the territory of a small backyard pond. Warm, calm, shallow waters are their favorite places. They can be found at lakes, ponds, rivers, or bogs.

They breed from May to August in Virginia. During breeding season the throat of the male Bullfrog is yellow, and the female's is white. Male bullfrogs chorus at breeding ponds and females give aggressive calls responding to the breeding calls of the males. The females are attracted to males with territories that provide the most food.

Fertilization is external, with females depositing up to 20,000 eggs in quiet and protected water. The egg mass is a large floating mat with a foamy film up to a yard wide. Fertilization is then accomplished usually by one male.

Tadpoles emerge about four days after fertilization and tadpoles may remain in the tadpole stage for almost 3 years before transforming into frogs. The longer the better for the frog since they will be bigger and have a better chance of survival. Adults reach sexual maturity after 3 to 5 years and have been recorded to live up to 7 years.

2 comments:

Anonymous said...

Bullfrog - Rana catesbeiana doesn't give of poisons. Stop spreading internet rumors.

Donna Watkins said...

The resource I took that tidbit of information from was allaboutfrogs.org. In searching just now, I don't see much else scientific that agrees with it.

There's a lot of talk about it on forums with people's opinions which of course are questionable.

On this PDF download about bullfrogs from conservancies.org, it states that bullfrogs are NOT poisonous:
Bullfrogs

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