A female American bullfrog can usually be identified by comparing her circular eardrum, called the tympanum, with her eye. In an adult female, the tympanum is approximately the same size as—or slightly smaller than—the eye. Females also usually have a white or cream-colored throat, while breeding males develop yellow throats. Scientifically known as Lithobates catesbeianus, the American bullfrog is a large, powerful aquatic frog native to eastern North America.
Female American Bullfrog Quick Facts
| Feature | Female American Bullfrog |
| Scientific name | Lithobates catesbeianus |
| Other scientific name | Rana catesbeiana |
| Tympanum size | About the same size as the eye |
| Throat color | White, cream, or pale |
| Adult length | Commonly 3.5–8 inches |
| Feet | Strong, extensively webbed hind feet |
| Main call | Does not normally make the male’s loud mating call |
| Reproduction | Lays eggs in a floating surface film |
| Egg number | Approximately 2,000–25,000 |
| Habitat | Ponds, lakes, marshes, reservoirs, and slow streams |
Size alone is not a dependable way to determine sex because males and females overlap greatly in body dimensions. The tympanum and throat color provide more useful clues in mature frogs.
What Does a Female American Bullfrog Look Like?
Female bullfrogs have broad heads, muscular bodies, smooth or slightly textured skin, and long hind legs. Their color varies from bright green to olive, brown, or gray, often with darker mottling.
Female Identification Features
- Tympanum approximately equal to or smaller than the eye
- White, cream, or pale throat
- Large, rounded body
- Green, olive, brown, or mottled upper surface
- Pale belly that may have gray or brown markings
- Large hind feet with extensive webbing
- No dorsolateral ridges extending down the back
- Fold of skin curving behind the tympanum
- No enlarged breeding pads on the thumbs
The absence of long dorsolateral ridges helps distinguish an American bullfrog from a green frog. In bullfrogs, the raised skin fold curves around the eardrum and ends near the shoulder instead of continuing along the back.
Female American Bullfrog vs Male
Adult bullfrogs display several visible differences, especially during the breeding season.
| Feature | Female | Male |
| Tympanum | About equal to the eye | Noticeably larger than the eye |
| Throat | White or cream | Usually yellow when mature |
| Advertisement call | Generally absent | Deep “jug-o-rum” call |
| Thumb pads | Not enlarged | Swollen nuptial pads when breeding |
| Territorial behavior | Usually less territorial | Defends calling and breeding areas |
| Main reproductive role | Selects mate and lays eggs | Calls, competes, and fertilizes eggs |
Tympanum Size
The tympanum is the round external eardrum positioned behind each eye. In an adult female, its diameter is approximately the same as the eye. A mature male commonly has a tympanum significantly larger than his eye and sometimes close to twice its diameter.
This is usually the best way to determine sex from a side-view photograph. However, the method is less reliable in juveniles because their adult sexual features have not fully developed.
Throat Color
A female normally has a cream, white, or lightly mottled throat. A sexually mature male commonly develops a yellow throat, particularly during the breeding season.
Lighting, mud, natural color variation, and the frog’s age can make throat color difficult to judge. Check the tympanum as well rather than relying on color alone.
Front Feet and Thumbs
Both sexes have four toes on each front foot and strongly webbed hind feet. During the breeding season, mature males develop swollen, grayish nuptial pads near the base of the inner thumbs. These pads help the male maintain his grip on a female during mating. Females do not develop the same enlarged breeding pads.
Do Female American Bullfrogs Croak?
Female American bullfrogs do not normally produce the loud, repeated advertisement call associated with males. The familiar deep call is made by males to attract females, communicate with rival males, and defend breeding territories.
Females are not completely silent. Research has shown that both male and female bullfrogs can produce release calls when grasped or disturbed. These shorter defensive sounds differ from the male’s powerful breeding call.
Therefore, hearing a bullfrog make a small grunt or release sound does not automatically prove it is male. Repeated, resonant calling from a breeding territory is much stronger evidence of a mature male.
Female Bullfrog Behavior
Female bullfrogs spend much of their time close to permanent or semi-permanent water. They often rest along muddy banks, among aquatic plants, beneath overhanging vegetation, or with most of their bodies submerged.
They are opportunistic predators and capture animals that can fit inside their mouths. Bullfrogs eat insects, spiders, crayfish, worms, smaller frogs, fish, and other small vertebrates. A recent dietary study found that adult females in two invasive Southern California populations contained more prey items than adult males, although body size did not differ significantly between the sexes in that study.
Female bullfrogs are generally less territorial than breeding males. Males occupy and defend shoreline calling areas, while receptive females approach breeding sites and select among available mates.
Female American Bullfrog Breeding
Breeding normally occurs during warm weather, although the exact timing varies with latitude, water temperature, and local climate. Males call from the water to attract females and warn competing males.
Mating and Amplexus
After selecting a mate, the female enters the male’s territory. The male climbs onto her back and grips her behind the front legs in a position called amplexus.
As the female releases her eggs, the male fertilizes them externally. The eggs spread across the water surface in a thin, floating film rather than forming a compact cluster attached beneath the female.
How Many Eggs Does a Female Lay?
A female American bullfrog may lay approximately 2,000–25,000 eggs during a spawning event. Washington wildlife authorities describe egg masses containing more than 6,000 eggs, while Minnesota records a broader potential range reaching 25,000.
The eggs hatch into aquatic tadpoles. Depending on climate, food, and water temperature, the tadpole stage may last through more than one growing season before metamorphosis.
Female American Bullfrog Habitat
Female bullfrogs occupy many freshwater environments, including:
- Permanent ponds
- Lakes and reservoirs
- Marshes and wetlands
- Farm ponds
- Slow-moving rivers
- Quiet stream margins
- Irrigation canals
- Artificial water features
American bullfrogs are native to much of eastern North America but have been introduced widely beyond their original range. In western regions, introduced populations may prey on native amphibians and other wildlife, making transport or release illegal in some jurisdictions.
Female Bullfrog or Green Frog?
Female bullfrogs are sometimes confused with female green frogs because both may have pale throats and similarly sized tympanums.
| Feature | Female Bullfrog | Female Green Frog |
| Back ridges | Absent | Usually extend along the back |
| Skin fold | Curves around tympanum | Continues behind tympanum |
| Adult size | Usually larger and heavier | Generally smaller |
| Body shape | Broad and heavy | More slender |
| Call | Female does not advertise | Female does not advertise |
The most useful distinction is the ridge pattern. A bullfrog lacks the paired dorsolateral folds running along the back, whereas a green frog normally has visible ridges extending behind the eardrum.
FAQs
How can you tell whether an American bullfrog is female?
Compare the eardrum with the eye. A female’s tympanum is approximately the same size as the eye, while a mature male’s is noticeably larger. Females also usually have white or cream throats rather than yellow ones.
Are female American bullfrogs larger than males?
Body size varies considerably, and the sexes overlap. Some populations may show average size differences, but size is unreliable for identifying an individual. Examine the tympanum, throat, and thumb pads instead.
Do female American bullfrogs make sounds?
Yes, females can make short release or defensive calls when grasped or disturbed. However, they do not normally produce the male’s loud, repeated “jug-o-rum” advertisement call used during breeding.
What color is a female bullfrog’s throat?
A mature female usually has a white, cream, or pale mottled throat. Adult males commonly develop a bright or dull yellow throat during the breeding season.
How many eggs can a female bullfrog lay?
A female may lay approximately 2,000–25,000 eggs in a thin film across the water’s surface. The exact number depends on her size, maturity, health, and breeding conditions.
