American Bullfrog: The Giant Frog With a Deep Call
What is an American bullfrog?
The American bullfrog is a large freshwater frog with the scientific name Lithobates catesbeianus. It is the largest frog species in the United States, and its deep call is one of the familiar sounds around warm ponds and lakes.
How big is an American bullfrog?
How large can this frog become? Adult American bullfrogs can reach about 8 inches in body length and weigh more than 1 pound. Their large head and powerful rear legs give them a heavy appearance compared with smaller North American frogs.
What color is an American bullfrog?
The American bullfrog has green or brown coloration, with darker markings across parts of the body. This coloring helps it blend with vegetation around ponds and other freshwater habitats.
What makes its body shape special?
The frog has a broad head, large eyes, strong hind legs, and fully webbed rear feet. Its rear legs provide the power for sudden jumps, while its webbed feet help it move through water.
Why are its eyes near the top of its head?
The eyes sit high on the skull, allowing the frog to watch its surroundings while keeping much of its body below the water surface. Frogs cannot turn their heads from side to side, so this eye position gives the bullfrog a wide field of view.
How can you tell a male from a female?
The round tympanum, or external eardrum, is larger than the eye in an adult male. In a female, the tympanum is about the same size as the eye or smaller.
Why does the male have a yellow throat?
An adult male develops a yellow throat during the breeding season. Females have white throats, making throat color a useful visual clue when identifying the sex of an adult bullfrog.
Where does the American bullfrog live?
The species is native to eastern and central North America. Its native range extends from Nova Scotia south toward Florida and west through parts of the central United States.
What habitats does the American bullfrog use?
American bullfrogs live around ponds, lakes, marshes, swamps, streams, rivers, and other freshwater habitats. Permanent water is especially useful because the tadpoles require a long period of development.
Where has the American bullfrog been introduced?
People have moved American bullfrogs outside their native range. Introduced populations occur in parts of the western United States, and the species has also been transported to areas outside North America.
Why are introduced bullfrogs a concern?
Large adult bullfrogs eat native amphibians and compete with smaller frogs for food and space. USGS researchers have studied these interactions in Washington, Oregon, Arizona, and other areas where the species was introduced.
How does an American bullfrog hunt?
The frog waits near water and watches for prey. When an animal comes within range, the bullfrog makes a fast movement and grabs it with its mouth and tongue.
What does an American bullfrog eat?
Its diet includes crayfish, water beetles, snails, dragonfly larvae, small fish, insects, worms, frogs, tadpoles, reptiles, birds, and small mammals. Larger bullfrogs also eat other bullfrogs.
Can an American bullfrog eat another frog?
Adult bullfrogs eat other amphibians, including frogs and tadpoles. This behavior becomes significant in places where bullfrogs have been introduced and native amphibians share the same ponds.
Can an American bullfrog eat a bat?
Animal Diversity Web records cases of bullfrogs eating bats. The species has a broad diet that reaches beyond insects and other small aquatic prey.
Do American bullfrogs eat their own species?
Cannibalism occurs in American bullfrogs. A large individual can swallow smaller bullfrogs and tadpoles.
What animals eat American bullfrogs?
Predators include snapping turtles, herons, foxes, raccoons, water snakes, and other animals that live around freshwater. Young bullfrogs and tadpoles face additional predators in the water.
Why do bullfrog tadpoles have an unusual defense?
Most fish avoid eating American bullfrog tadpoles because of their unpleasant taste. This gives the tadpoles protection from a predator that eats the larvae of other frog species.
When does the American bullfrog breed?
Breeding occurs during the warmer months. In northern parts of the range, breeding takes place from May through July, while southern populations have a longer breeding period.
How does the male attract a female?
The male produces a deep call that sounds like “jug-o-rum.” The call attracts females and also communicates ownership of a breeding territory.
How far can an American bullfrog call travel?
The deep male call can travel more than 1 kilometer under suitable conditions. The sound carries across open water and helps females locate calling males.
How large is a male bullfrog territory?
Animal Diversity Web reports defended shoreline territories ranging from 3 to 25 meters. Males can fight other males that enter these areas.
How many eggs does a female American bullfrog lay?
A female can produce about 12,000 to 20,000 eggs in a floating egg mass. The eggs remain near the surface of calm freshwater during early development.
How are the eggs fertilized?
Fertilization takes place outside the female's body. The female releases eggs into the water while the male releases sperm over them.
How fast do American bullfrog eggs hatch?
Under suitable conditions, the eggs hatch after about 4 days. The young emerge as tadpoles with tails and gills adapted for life in water.
How long does the tadpole stage last?
The tadpole stage is long compared with that of several other frogs. American bullfrog tadpoles can spend about 2 winters in the water before completing metamorphosis.
When does an American bullfrog become sexually mature?
Sexual maturity is reached at about 3 to 5 years. Growth speed differs between populations because temperature, food availability, and local conditions affect development.
How long does an American bullfrog live?
American bullfrogs live around 8 years according to the National Park Service. Animal Diversity Web lists a captive lifespan reaching 16 years.
How does an American bullfrog survive winter?
The frog enters a period of reduced activity during cold weather. It can remain beneath mud or other wet shelter while temperatures are low.
Can an American bullfrog breathe underwater?
The frog does not use its lungs to breathe underwater. It also absorbs oxygen through its moist skin, which allows gas exchange directly between the water and its blood.
Why does the bullfrog's throat move so much?
Frogs do not have a diaphragm or ribs that work like the human breathing system. Their throat movements push air into and out of the lungs.
Are American bullfrogs harmless?
An American bullfrog is not considered dangerous to people under normal conditions. It is a predator, however, and an adult can swallow animals that are surprisingly large compared with its own head.
Is the American bullfrog dangerous to native wildlife?
The answer depends on location. In its native range it is part of the local ecosystem, while introduced populations have been associated with predation and competition involving native amphibians.
Can American bullfrogs carry disease?
American bullfrogs can carry pathogens such as the amphibian chytrid fungus Batrachochytrium dendrobatidis. USGS research has examined bullfrogs as hosts and possible sources of pathogens affecting native amphibians.
What did researchers find at 233 sites?
A USGS-led study examined 233 sites in the southwestern United States and Sonora, Mexico, during 2016 to 2018. Chiricahua leopard frogs were detected at 32% of sites without bullfrogs compared with 4% of sites where bullfrogs occurred, while Western tiger salamanders were detected at 36% and 18% of those site groups respectively.
Does every study show the same effect?
No. The USGS study found clearer negative associations for two native amphibians, while evidence for two leopard frog species was less clear. Habitat overlap and differences in detection affected the results, so the relationship between bullfrogs and native amphibians is not identical at every location.
Why are American bullfrogs difficult to control?
The species produces large egg masses, reaches a large adult size, and uses permanent freshwater habitats. USGS researchers are studying removal methods in places where introduced bullfrogs threaten native amphibians.
What happened after bullfrogs were removed in Arizona?
One USGS study examined 19 bullfrog-removal sites and 18 control sites between 2016 and winter 2020–2021. Bullfrogs were successfully eradicated from 94% of the treatment sites, while two pathogens disappeared from the treated sites along with the bullfrogs.
What should you do if you find an American bullfrog?
Leave the frog where it is if you are simply observing wildlife. Do not move it to another pond or release it into a new waterway.
What if the frog is outside its native range?
Contact the local wildlife agency or invasive-species program before moving the animal. Local regulations differ, and transporting an introduced frog can help spread the species or pathogens.
Why should people avoid releasing pet bullfrogs?
A released bullfrog can establish a population in freshwater habitat where the species did not occur naturally. The U.S. Geological Survey identifies pet releases and fishing bait among human pathways that can introduce bullfrogs.
Are American bullfrogs endangered?
The American bullfrog is listed as Least Concern by the IUCN. It is widespread across its native range and has established populations outside that range.
When did American bullfrogs reach the western United States?
Introductions into western parts of the United States began during the early 20th century. Human activities then helped the species spread into additional freshwater habitats.
What is the older scientific name for this frog?
Older scientific literature frequently used the name Rana catesbeiana. Modern taxonomic treatment places the American bullfrog under the genus Lithobates, giving the current name Lithobates catesbeianus.
Who photographed the American bullfrog used with this article?
The Wikimedia Commons photograph titled “Stanton Lithobates catesbeianus 3.jpg” was photographed by Rstanton13 on 16 July 2024. The file is published under the Creative Commons Attribution-ShareAlike 4.0 International license.
Photo source: Wikimedia Commons — Stanton Lithobates catesbeianus 3.jpg
Sources:
- Animal Diversity Web — American Bullfrog
- National Park Service — American Bullfrogs Fast Facts
- U.S. Geological Survey — American Bullfrog and Native Amphibians
- U.S. Geological Survey — American Bullfrog Invasion and Impacts
- U.S. Geological Survey — Bullfrog Eradication and Pathogens
Source: Animal Diversity Web
0 Comments