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American bullfrog’s loud deep call a classic in Hutto

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Posted: Saturday, September 29, 2012 11:10 am

When we first moved to Hutto, one of my favorite night sounds was the bullfrog’s low, beautiful call.

The American Bullfrogs (Rana catesbeiana) is the largest North American frog. It is considered a “true” frog because of its long legs, and powerful jumping ability.

Females can get as large as eight inches long compared with males at seven inches. The external eardrums (tympanum) are circular and found just behind the eyes. The male tympanum are as large as the eyes, while the female eardrums are smaller.

The bullfrog call is actually a love song to attract a mate. The loud deep call can be heard up to a mile away.

Males have several mating opportunities each year, but the females only mate once or twice. She has to be very selective in choosing the most dominant male in order for her offspring to be strong enough to survive.

Older females sometimes sing making the competition stiffer among the males.

The female lays up to 20,000 eggs, which hatch into tadpoles. The eggs are attached to underwater plants and taste bad to predators.

Tadpoles eat mostly algae and underwater plants, but occasionally eat small aquatic invertebrates or tadpoles of other species. Bullfrog tadpoles can grow up to five inches in length. The tadpoles also have a bad taste, but snakes, turtles, fish and birds will eat them.

Metamorphosis can happen in a matter of weeks or can take up to two years. The length of time before metamorphosis determines the size of the adult bullfrog.

Adult bullfrogs are aggressive predators eating any animal they can swallow, including insects, crayfish, worms, minnows, other frog species, small turtles, snakes, baby birds, and even mice.

They hunt by ambush, quietly watching and waiting for prey to pass near, and then lunging with their powerful hind legs capturing the prey with their wide, open mouths. Great blue herons and raccoons catch and eat adult bullfrogs.

Bullfrogs prefer to live around permanent water sources such as lakes, ponds, rivers, and streams.

While bullfrogs are native in the central and eastern parts of the United States, they are considered an invasive species in other parts of the country because they eat other smaller native amphibian species.

Sometimes they are released accidentally during trout stockings. They have been introduced both by fishermen who use tadpoles as bait and when people want to raise bullfrogs to harvest for frog legs, a delicacy food for humans.

In Texas, bullfrogs are on the White List for nongame wildlife. To possess more than 25, one must purchase a nongame wildlife permit. There is also a dealer nongame permit to sell nongame wildlife.

Bullfrogs are used for medical research and also for dissection in many high school biology labs.

Texas has an Amphibian Watch citizen science program that monitors amphibians around the state.

For those interested in learning more about Texas amphibians such as the cricket frog, leopard frog, and Gulf coast toad, there is a monthly Amphibian Watch at Berry Springs Park in Georgetown.

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