Wonders of Wildlife: American Bullfrog

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American Bullfrog

Scientific Name: Lithobates catesbeianus

Found in Alabama: common statewide

Diet: Herbivore (eats plants) as tadpoles
Carnivore (eats animals) as adults

American Bullfrog in Habitat – Public Domain Photo

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Classification

IDENTIFICATION

Adaptations

Life Cycle

Basic Needs

Ecological Role

CLASSIFICATION

Scientists use basic traits to
group animals into different taxonomic
classes.

For a taxonomic classification chart comparing key traits of common backyard wildlife,
CLICK HERE!

What type of animal am I?

I am a vertebrate (an animal with a spine or backbone).
I am cold-blooded, so I cannot control my body temperature.
I do not have scales, feathers, or fur, so I have smooth skin.
When I am a larva (tadpole), I breathe using gills, and when I am an adult frog, I breathe using lungs.
I have 4 legs.

The American Bullfrog is an AMPHIBIAN!

IDENTIFICATION TIPS

American Bullfrog – Wikimedia – Will Brown

ADULT AMERICAN BULLFROG

Largest frog in the United States with body size ranging from 3.5 – 8 inches long (18 inches with legs extended)
Brownish green on back and greyish white on belly
Large tympanum (eardrum) and webbed hind feet

FEMALE

Throat is less yellow in coloration
Tympanum (eardrum) appears around the same size as the eye

Female and Male American Bullfrogs – Wikimedia – B. Kimmel

MALE

Yellow coloration on the throat
Tympanum (eardrum) appears larger than the eye

EGGS

Under 0.5 inches in diameter

American Bullfrog Eggs – Dreamstime

TADPOLES (Larvae)

Up to 6.75 inches in length

American Bullfrog Tadpole – Wikimedia – Dave Huth

FROGLETS

Range from size of tadpole to
8-inch-long body

American Bullfrog Froglet –
Tyler Burgener

PHYSICAL AND BEHAVIORAL ADAPTATIONS

Frog Life Cycle – Dreamstime
Click To Enlarge

PHYSICAL ADAPTATIONS

American bullfrogs have webbed hind feet:

The hind feet of American Bullfrogs are fully webbed, allowing them to easily move around in their aquatic (water) habitat.

American bullfrogs have specialized ears:

Frogs do not have ears like humans’ ears. We have flexible (bendable), external ears on the outside of our head, and then down inside our ear we have eardrums (tympanums) that collects sound. (CLICK HERE for more details.)
Frogs do not have external ears like ours, but you can see their tympanum (eardrum) as it is the round, circular shape on both sides of their head which allows them to hear.

American bullfrogs have tongues that help them capture prey:

The tongue of an American bullfrog is long and is attached at the front of the mouth, allowing it to launch as far as possible to capture prey (animals they eat).
Frog tongues are made of extremely soft tissues, giving them the ability to hold on to the prey.
Their tongues are not “sticky” like a piece of tape. Instead, their saliva is able to convert back and forth between a liquid watery texture and a thick, sticky texture.
When a frog is at rest, the saliva is watery and not sticky. As a frog sticks out its tongue to capture prey (animal that it eats), the liquid saliva that surrounds the animal becomes thicker and stickier, trapping the animal.
Once the animal is inside the frog’s mouth, the frog uses its eyes to push against the food item to help release it from the tongue, allowing the frog to swallow its food.

American bullfrogs have four teeth to hold their prey in their mouths:

American bullfrogs have teeth in the middle of the roof of their mouth and in the front of the top of the mouth.
They use these teeth to keep their prey (the animals they eat) from escaping while they can swallow them.

BEHAVIORAL ADAPTATIONS

American bullfrogs are cathemeral:

They are active during the day and night (cathemeral).

American bullfrogs hibernate:

he American Bullfrog is cold-blooded and does not produce its own body heat like we do.
During cold winter months, it protects itself by hibernating or becoming dormant as if it is in a deep sleep.
Their breathing and heartbeat slow down during hibernation like your breathing and heartbeat slows down while you are asleep.
Adult frogs hibernate in a burrow or cave-like structure that it builds in the mud at the bottom of a pond (or other water source) or under leaf litter.
They emerge and become active when the weather is warm and food sources become available.

American bullfrogs communicate with one another:

The main form of communication happens in the warm summer months during the breeding season when the male frogs want to mate with the female frogs.
Males sit in shallow water and make a deep call that sounds like “jug-o-rum”.
When an American bullfrog is captured by a predator that wants to eat it, it makes a loud screeching sound to warn other frogs about the predator.

Male American bullfrogs are territorial:

Male American bullfrogs are territorial and will agressivly defend their territory where they live.
They defend their territory by making loud sounds or vocalizations, using physical displays like puffing up their throat, and chasing or wrestling with other male frogs who are competitors competing for the females.
Females select males that have the territories with the most food.

American Bullfrog Eating
a Northern Leopard Frog – Alison Ainsworth – Project Noah

American bullfrogs are predators:

American Bullfrogs are sit-and-wait predators that wait for prey (animals they can eat) to come near them rather than actively hunting.
When prey comes close to a bullfrog, the bullfrog will leap using its long hind legs, jumping up to 10 times their body length. This is equivalent to a 6 foot tall human jumping 60 feet or to the top of a tall tree!
Once the prey is captured, they use their strong tongues to flip the prey into their mouths.
They also have teeth on the roof of their mouth to help prevent the prey from escaping once captured.

LIFE CYCLE

American Bullfrog Metamorphosis – Tyler Burgener

Metamorphosis is the process of physical change that some animals go through as they transform from a larvae into an adult.

Four Life Cycle Stages of the American Bullfrog

Stage 1: Egg

Females lay up to 2,000 soft-shelled eggs each breeding season.
Eggs are laid in a foamy film on top of quiet, still waters.

Stage 2: Tadpole

Once the larvae (tadpoles) emerge from the eggs, they are independent and can live in an aquatic (water) habitat as a tadpole for up to 3 years.
Tadpoles do not have lungs.
They do not breathe like we do.
They have gills like fish for breathing.

Stage 3: Froglet

As a tadpole undergoes metamorphosis
(physical changes)
from tadpole to adult, it grows hind legs and front legs
as the tail begins to shorten.
The gills will reduce as the lungs begin to enlarge.
During this transition, the American Bullfrog goes through
the froglet stage where they begin to resemble the adult
but have not fully developed all of the adult features.

Stage 4: Adult

Adult American bullfrogs have fully formed legs and lungs and are able to live on land.

Lifespan

American bullfrogs have a lifespan of 7-9 years.

HABITAT NEEDS

Natural Habitat Needs	Adults	Young
Food	Will eat nearly anything that they can fit in their mouth including insects, other frogs, salamanders, small snakes and turtles, and even small birds. Are cannibalistic (eat other bullfrogs).	Feed on aquatic plants and algae that live in ponds, streams and other bodies of water.
Water	Absorb water through their skin like a sponge. Live in or near bodies of freshwater including lakes, ponds, rivers, and bogs (a type of wetland). (Note: They will die in saltwater like ocean.) Prefer warm, calm, shallow waters.	Absorb water through their skin like a sponge. Live in or near bodies of freshwater including lakes, ponds, rivers, and bogs (a type of wetland). (Note: They will die in saltwater like ocean.) Prefer warm, calm, shallow waters.
Shelter	Hide in vegetation around water source or underwater.	Tadpoles live in bodies of water. Aquatic vegetation (plants) may provide a source of protection.
Places to Raise Young	Deposit eggs in most bodies of freshwater with vegetation (aquatic plants). Prefer warm, calm, shallow waters are preferred. After hatching from the eggs, tadpoles remain in the water until they develop and grow legs and lungs.

If you want to offer resources in your backyard habitat for this species, consider the suggestions below.

Backyard Habitat Needs	Adults	Young
Food	Provide a shallow pond that will attract insects that lay their eggs in water like dragonflies, and they will eat the insect eggs and larva (baby insects) called macroinvertebrates. Provide aquatic (water) plants, terrestrial (land) plants, and habitat that attract insects, frogs, salamanders and small birds for the bullfrogs to eat. See AWF's Frog Habitat Project Plan for a list of materials & plant suggestions.	Provide a shallow pond that is able to support algae and aquatic vegetation (plants).
Water	Provide a water source such as a shallow pond that is able to support algae and aquatic vegetation (plants).	Provide a water source such as a shallow pond that is able to support algae and aquatic vegetation (plants).
Shelter	Plant marginal plants around or aquatic plants in sources of water such as a shallow pond. If in danger, they are likely to seek shelter in grassy areas or by jumping in the water.	Provide a water source such as a shallow pond with aquatic vegetation (plants) where the tadpoles can hide.
Places to Raise Young	Provide a source of water such as a shallow pond in which females can lay their eggs.

ECOLOGICAL ROLE

Food Source:

Bullfrogs are a food source for a variety of animals including herons, egrets, turtles, water snakes, racoons, kingfishers.
Fish typically do not eat bullfrog tadpoles because they taste bad.
Humans also hunt bullfrogs and eat their hind legs.

Insect Population Control:

Bullfrogs eat a lot of insects which helps control the insect populations and reduce the number of insects.

Human Use:

Humans use bullfrogs as a food source.
Humans also use them quite often for medical research because their skeletal, muscle, digestive, and nervous systems are similar to those of other animals.

Indicator Species:

The thin skin on adult American bullfrogs and other amphibians makes them susceptible to absorbing toxic materials and pollutants present in the environment.
A decrease in population size might indicate an increase in harmful chemicals in an ecosystem.

Invasive Species:

Bullfrogs are very tough and can survive in most habitats.
This has led to them being invasive in many locations where they have been introduced (including the western U.S.).
They have such big appetites and are such successful predators that their presence can lead to the decline or elimination of other amphibian species and some reptile species.

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