Complete Guide To The Bullfrog
Bullfrog Images
How To Identify Bullfrogs
Bullfrog Notes
Bullfrog Classification
Quick Facts About Bullfrogs
|
Scientific Name |
Lithobates catesbeianus (formerly Rana catesbeiana) |
|
Common Name(s) |
American Bullfrog |
|
Animal Type |
Amphibian |
|
Diet |
Carnivore |
|
Lifespan |
5 years or more in the wild (Tyning 1990) |
Bullfrog Image Gallery
How To Identify Bullfrogs
- Bullfrogs are the largest type of frog in North America and can grow up to 8 inches (20.3 cm) long.
- Females grow larger than males and have smaller tympanums, and slimmer forearms (Martof et al. 1980).
- Most of the largest individuals are females, since males are more active out in the open and thus, more exposed to predators (Tyning 1990).
- They are stout-bodied and have:
- Green heads.
- Males have yellow throats; females have throats that are pale yellow to white.
- Gold eyes with black pupils.
- Very large tympanums.
- Male tympanums are larger than their eyes; female tympanums are about the same size as their eyes.
- A thin ridge of skin that runs behind each eye, behind each eardrum, and ends at the base of each fore leg.
- Brown, green, or olive green bodies.
- The base of the thumb on male forelegs is dark and enlarged compared to that of females.
- Smooth backs that lack dorsolateral ridges seen in other frog species.
- Hind legs either banded or blotched in brown and green.
- Long, muscled hind legs tipped with feet that are fully webbed except for the last joint of their longest toe.
- Green heads.
- Like the adults, Bullfrog tadpoles are the largest tadpole in North America. They grow startlingly large.
- The tadpole pictured in the photo gallery was about 6 inches (15.2 cm) long and had a head about the size of a golf ball.
How To Find Bullfrogs
Look for Bullfrogs in ponds, lakes, and slow-moving streams throughout North Carolina during the summer months.
Bullfrogs are most active at night. They rest partially submerged out in the open during the day but spook easily and from some distance away. I’ve found it almost impossible to sneak up on a Bullfrog. I recommend using binoculars or a telephoto camera lens to search the banks of ponds and lakes, especially areas with lily pads or aquatic plants that stick up out of the water.
Otherwise, you’re likely to hear only the distinctive “ker-plunk” these large amphibiams make as they disappear into the watery depths.
What Bullfrogs Eat
Adult Bullfrogs prey mostly on insects, crayfish, small fish, and other frogs, like the Green Frog (Lithobates clamitans). But some individuals can grow large enough to catch and eat young snakes and even small birds (Behler and King 2020).
Bullfrog tadpoles eat bacteria and microorganisms that live in the material on pong bottoms and along underwater plant stems.
What Eats Bullfrogs
Bullfrogs are, in turn, eaten by many larger predators, such as:
- Birds, like Great Blue Herons (Ardea herodias) and Great Egrets (Ardea alba)
- Reptiles, especially Snapping Turtles (Chelydra serpentina)
- Mammals, like Raccoons (Procyon lotor), Northern River Otters (Lutra canadensis) and Minks (Mustela vison).
Bullfrogs make very attractive meals for their predators, thanks to their large size. So Bullfrogs live in large ponds and lakes that have lots of vegetation in which they can hide, and are very quick to swim or jump away from anything they consider threatening.
Bullfrog Behavior And Life Cycle
Bullfrogs breed from early spring to late fall in North Carolina.
Male Bullfrogs entice females to mate by singing loud choruses, especially at night, and by maintaining the best territories. Males compete for breeding territories that range in size between six and twenty feet in diameter. Bullfrogs prefer to communicate dominance through their songs but will fight physically if the vocal warnings don’t convince encroaching males to back off.
Physical fights between male Bullfrogs can be dangerous for both combatants. Bullfrogs wrestle and try to gouge each other with their thumbs. Fights can last for several minutes and usually end with one of the combatants hopping off in defeat (Tyning 1990), sometimes with significant injuries, especially to their eyes.
Smaller males invading the territories of large, dominant males may be either not challenged at all or chased out of the territories quickly without much physical contact.
Female Bullfrogs watch and listen to the males’ behavior very carefully throughout the breeding season and select the males with whom they breed carefully. Reproduction is costly for female Bullfrogs because each female lays approximately 12,000 eggs. Males clasp the females tightly and fertilize their the eggs as the females release the eggs into the water (Tyning 1990).
Bullfrog eggs hatch after about five days and the tadpoles metamorphose into adult frogs a year later (Martof et al. 1980).
Fun Facts About XXXX
Humans have introduced the Bullfrog into areas beyond its traditional, native range for food production and through irresponsible pet trade and pet owner practices.
The biological invasion of non-native animals usually hurts native animal populations in some way, such as out-competing the natives in some way, predating the native species, or carrying diseases for which the native species have no natural immunity.
Unfortunately, Bullfrogs tick all these boxes.
First, because they are so big throughout each of their life stages, Bullfrogs are voracious eaters that consume a great deal of food, and can consume creatures up to nearly their own body size. This includes their smaller frog cousins, like Green Frogs (Lithobates clamitans), and even other Bullfrogs.
Second, Bullfrogs carry a pathogenic, chytrid fungus called Batrachochytrium dendrobatidis (“Bd” for short) that kills other amphibians (Miaud et al. 2016).
However, nature is always more complex than it appears at first glance, and the invasion of Bullfrogs into non-native environments is no exception. Some animal species seem to be helped by invasive Bullfrogs.
In one study of invasive Bullfrogs in Uruguay, three fish species in family Characidae appeared to be positively affected by the presence of Bullfrogs, possibly because these fish are not consumed by Bullfrogs (unpublished data). The fish in ponds that included Bullfrogs grew substantially larger than the fish in ponds that included only native species:
- Cheirodon interruptus grew 16% larger
- Hyphessobrycon anisitsi grew 30% larger
- Astyanax laticeps grew 47% larger (Gobel, Laufer, and Cortizas 2019, https://doi.org/10.1007/s00027-018-0604-1).
Bullfrog Classification
|
Phylum |
Chordata |
|
Class |
Amphibia |
|
Order |
Salientia |
|
Family |
Ranidae (True Frogs) |
|
Genus |
Lithobates (formerly Rana) |
|
Species |
L. catesbeianus (formerly R. catesbeiana) |
Binomial Name |
Lithobates catesbeianus (formerly Rana catesbeiana) |
