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Bullfrog

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Bullfrog
North American Bullfrog.jpeg
Scientific Classification
Scientific Name

Lithobates catesbeiana

Male North American Bullfrog.jpg
Male North American Bullfrog

The American Bullfrog is a species of frog known by the scientific name Lithobates catesbeiana. They are perhaps best known for their large size and loud, signature croaks. Their croaks are so powerful that they can be heard from miles away. Some people say it sounds like a cow mooing - thus their name bull-frog. Bullfrogs are three to six inches in length and weigh 750 grams.

They are also known for being the world's most dangerous invasive species on the planet. They can adapt to almost any environment and can eat about anything from insects to birds. The males mate with the females during early summer. The females will lay up to 20,000 eggs. [2]

Body Design

North American Bullfrog Eardrum

The North American Bullfrog has many amazing characteristics. Bullfrogs can range between 3.6 and 6 inches in length, with their legs adding another 7-10 inches. That's a 16 inch maximum length! They weigh up to one pound and are the size of an adult male's hand. To tell if a bullfrog is a male or a female look at the bullfrog’s eyes and if the eardrum (tympanum) is larger than the eyes than it is a male. If the eardrum (tympanum) is smaller, it is a female.[3] Refer to the image on the right. Male and female bullfrogs have different colored throats during their mating season. The male has a yellow throat and the female has a white throat. Bullfrogs have either brown or gold eyes and it doesn’t matter if it is a male or a female. [4]

A bullfrog’s legs are so powerful that they can soar up to three to six feet in the air. [3] Bullfrogs do not have many predators, because their skin produces a toxic waste when threatened. [5] They do not breathe under water with their nostrils, but they can breathe through their skin. The bullfrog's tongue is attached at the front of its mouth unlike a human tongue which is attached at the back. Their tongue moves as fast as a blink of an eye.

Life Cycle

North American Bullfrog Tadpole

The Life cycle of the North American bullfrog begins when the female lays masses of 20,000 to 25,000 eggs in the water. The eggs clump together to form what looks like a "floating white sheet". These eggs are subject to much predation as many are eaten before they are able to hatch [6] . After a few days, the surviving babies hatch from the eggs as tadpoles or polliwogs. The tadpoles have a long tail and slender body that they use to swim through the water, and gills that they breathe water through. After about one year of eating plants they begin metamorphosis and grow legs, and then shortly after that, grow arms. The tadpole's tail then begins to shorten and develops lungs as its gills begin to disappear, but still remains in the water. The tadpole, now called a froglet, is almost fully mature, It can walk on land and breathe oxygen and still has a small tail. After 2-3 years of metamorphosis, the frog is mature and lives on land. [7]

The North American bullfrog mating season begins in May to July in the North, and February to October in the South. Reproduction is external, and begins with the male laying on top of the female and wrapping its arms around the female's abdomen. The female will then release its eggs into the water as the male releases its sperm into the water, fertilizing the eggs. After fertilization, the male stays behind to protect the eggs and to mate with the females once hatched. [8] Bullfrogs were named for their loud croak, because it sounds like the roar of a bull. [9] Bullfrogs are also reclusive, and rarely interact with other members of the same species outside of mating. Bullfrogs are also very territorial, and aggressively attack any intruding on their Home Range (territory). [10] In the fall or winter, bullfrogs may burrow in the mud until spring, however, in some warm climates, bullfrogs may stay active all year. Bullfrogs are fierce predators and prey on snakes, worms, insects, crustaceans, tadpoles, aquatic eggs of fish, and even salamanders. Bullfrogs are also cannibalistic and will not hesitate to eat members of their own kind. [11]

Ecology

map of North American Bullfrog habitats throughout America

North American Bullfrogs like to eat live insects, such as crickets, spiders, slugs, etc. [12] They are particularly greedy; if they are capable of eating something, they will. Some of their stomachs have been found to contain small rodents, turtles, snakes, birds, and even, on rare occasion, bats. Cannibalism is common among this species. They also eat aquatic animals and plants, since it lives particularly in aquatic surroundings. In tadpole form they are mostly herbivorous, feeding on algae and other aquatic-related vegetation. One of the primary roles that they perform in their environment is to help control excessive populations of particular insects, which are a large part of their diets.[13]

They live in aquatic environments such as lakes, rivers, ponds, slow-moving streams, etc., and have been introduced to different continents (Asia, Europe, South America, etc.) other than North America. Bullfrogs are becoming more common in areas that humans continue to build in; the construction often causes water temperatures and vegetation growth to go up. Bullfrogs prefer such conditions. These habitats are good for the reproduction and maturation of bullfrogs. [14] They keep away from cold or dry conditions since water is essential for breeding. Its predators include humans, who hunt them for their legs, and a wide variety of different animals depending on the environment it lives in. Of course, as mentioned before, they also will not hesitate to eat their own kind. Fish often avoid North American Bullfrog tadpoles because of their unpleasant taste. [15]

Invasive Species

Location and Method of Introduction

There were different methods of accidental introduction of the North American Bullfrog. They have thrived in California, though their original home is in the eastern part of North America. They sometimes invade fish hatcheries in their greediness to eat. While inside the ponds, their larvae are occasionally separated with the fish that are routinely stocked in areas where they are scarce. Some are kept as pets but are then released into the wild. Others are placed in different habitats intentionally for the sake of commercial hunting. As mentioned earlier, the bullfrogs are welcome to eat anything they can fit down their throats, and so are put into habitats that are overcome by insect or rodent pests for population control. As mentioned before, bullfrog tadpoles taste bad to fish that inhabit the same waters they do, and so they increase because of the lack of predators. [16]

Environmental Impact

The bullfrog is dangerous to North America because of its aggressiveness and lack of predators. The bullfrog is a predator to garter snakes, other frogs, fish, insects and water birds. Also, disgustingly enough, they will eat other bullfrogs. Bullfrogs can easily adapt to any environment, even one that is polluted by humans. The bullfrog mating seasons is from late May to July and lay up to 20,000 eggs per season. Since they don’t have predators the tadpoles have a higher chance of living, which increases the population. [17]

Control Methods

Their lack of predators, and ability to relocate has made the North American Bullfrog an especially difficult species, and no single method has proved effective. Some toxic chemicals, such as Rotenone can be applied to bullfrog infested waters, but bullfrogs can avoid it by simply jumping out of the water. However, some researchers at the Buenos Aires National Wildlife Refuge have found success in draining Bullfrog infested ponds, killing the tadpoles, and rounding up the remaining Bullfrogs. When Monsoon season comes, the drained ponds fill up, and the researchers can reintroduce Native species such as Leopard frogs.[18]

Video

The North American bullfrog diet and hunting tactics

References

  1. Lithobates catesbeiana Wikispecies. Web. Last edited March 25, 2017. Unknown Author.
  2. American Bullfrog Nature Mapping Foundation. Web. Accessed November 13, 2017. Unknown Author.
  3. 3.0 3.1 Hall, Madeleine The Characteristics of a Bullfrog Cuteness. Web. Accessed November 5th 2017.
  4. American Bullfrog Pace. Web. Accessed November 5th 2017. Unknown Author.
  5. American Bullfrog Facts Softschools. Web. Accessed November 5th 2017. Unknown Author.
  6. The Bullfrog Lifecycle. SK Creations, Inc. Web. November 5th, 2017 accessed. Author unknown.
  7. Bullfrog Lifecycle. Wordpress. Web. November 5th, 2017 accessed. Author unknown.
  8. Bruening, S. 2002. Lithobates Catesbeianus. Animal Diversity Web. Web. November 5th, 2017 accessed.
  9. Reproduction. Weebly. Web. November 5th, 2017 accessed. Author unknown.
  10. American Bullfrog Lithobates catesbeianus. The Regents of the University of Michigan. Web. November 5th, 2017 accessed. Author unknown.
  11. Bruening, S. 2002. Lithobates Catesbeianus. Animal Diversity Web. Web. November 5th, 2017 accessed.
  12. The American Bullfrog Information Sheet. Mircosoft Word. Web. November 5th, 2017 accessed. Author unknown.
  13. American Bullfrog Fact Sheet. Jessie Hale - Blog. Web. November 5th, 2017 accessed. Author unknown.
  14. Bruening, Sandra . Lithobates Catesbeianus American Bullfrog. Animal Diversity Web. Web. November 5th, 2017 accessed.
  15. American Bullfrog. Wildscreen. Web. November 5th, 2017 accessed. Author unknown.
  16. Murphy, Martin. Introduced Species Summary Project North American Bullfrog (Rana castebeiana). Web. February 17th, 2003 last edited.
  17. Murphy, Martin Introduced Species Summary Project Columbia. Web. Last edited February 17, 2003.
  18. Invading Bullfrogs Appear Nearly Unstoppable. Web. Accessed November 7th, 2017. Author Unknown.