The American bullfrog is the largest true frog in North America. Adults usually measure 9 to 15 cm (3.6 to 6 inches) from snout to vent and can weigh up to 500 g (1.1 pounds), with rare giants reaching 800 g. Males get their name from a deep, bellowing call that sounds like a bull. Bullfrogs eat nearly anything they can fit in their mouths, their tadpoles can take up to three years to change, and they’ve become an invasive species in more than 40 countries.
Here are the details.
What is an American bullfrog? #
The American bullfrog, Lithobates catesbeianus (some sources still use the older name Rana catesbeiana), is a large aquatic frog native to eastern North America. According to Wikipedia’s bullfrog article, it’s found in every U.S. state east of the Mississippi River, and its native range reaches north into Canada’s Maritime provinces.
Bullfrogs live in and around permanent water: ponds, lakes, marshes and slow rivers. They need water that lasts all year, because their tadpoles take so long to grow.
How big do bullfrogs get? #
| Measure | Typical adult | Large adult |
|---|---|---|
| Snout-to-vent length | 9 to 15 cm (3.6 to 6 in) | Up to 20 cm (8 in) |
| Weight | Up to 500 g (1.1 lb) | Up to 800 g (1.8 lb) |
Legs are extra. A big bullfrog with its hind legs stretched out is a lot longer than those body measurements suggest.
Why is it called a bullfrog? #
Because of the male’s call. During the breeding season, males make a low, droning bellow that people compare to a bull. It carries a long way across still water on summer nights, and it’s the sound many North Americans picture when they think of a pond at night.
You can tell males from females by the eardrum, the round disc behind the eye called the tympanum. In males it’s bigger than the eye. In females it’s about the same size as the eye.
What do bullfrogs eat? #
Almost anything. Bullfrogs are generalist carnivores that sit and wait, then lunge at whatever moves within range. Their diet includes:
- insects and other invertebrates
- crayfish
- other frogs, including smaller bullfrogs
- snakes
- rodents
- birds
Cannibalism has been observed where food is scarce. That appetite is a big part of why bullfrogs cause problems outside their native range.
How long do bullfrog tadpoles take to become frogs? #
Longer than most frogs. Bullfrog tadpoles take anywhere from a few months in the warm south of their range to three years in the north. That’s why they need permanent water: a pond that dries up in summer would kill a tadpole that still has two winters to go. For comparison with other frogs, see how long it takes a tadpole to become a frog.
How many eggs does a bullfrog lay? #
A lot. A female can lay between 1,000 and 40,000 eggs, which form a thin floating sheet on the water that can cover half a square meter to a full square meter. The eggs hatch in 3 to 5 days. Most of the tadpoles get eaten, but the sheer numbers mean a pond can fill up with bullfrogs quickly.
What eats bullfrogs? #
Plenty of animals, especially when bullfrogs are young. They’re an important prey item for many birds, particularly large herons, and for North American river otters and predatory fish. Other amphibians, including bigger bullfrogs, eat them now and then too.
How long do bullfrogs live? #
Wild bullfrogs are estimated to live 8 to 10 years at most, and one in captivity lived almost 16 years.
Why are bullfrogs invasive? #
People moved bullfrogs around the world on purpose, mostly as a source of food and sometimes as a form of biological pest control. They’ve now been introduced to more than 40 countries, and within North America to much of the western U.S., including California, Arizona, Oregon and Washington.
Once established, they’re hard to stop. Their huge clutches let populations grow fast, and their appetite means they eat or outcompete native frogs, turtles and snakes. Introduced bullfrogs have also been known to spread chytrid fungus (Batrachochytrium dendrobatidis), a pathogen that has hit amphibian populations hard. That’s why many regions ask people not to release bullfrogs, and some actively remove them.
Are bullfrogs good or bad for a garden pond? #
In their native range, a bullfrog in a big pond is part of a normal ecosystem. In a small garden pond, a bullfrog can eat your fish, your other frogs and anything else it can catch. Outside their native range, wildlife agencies generally ask people not to move or release them. Check your local rules before moving any frog from one pond to another.
Is there a bullfrog in Frog Pond? #
Yes, and it’s one of the first frogs you’ll hire. In Frog Pond, a cozy idle game about building a pond full of frogs, the Bullfrog is the second worker tier: “Croaks loudly, eats faster than you’d think,” which fits the real animal well. It arrives at Pond Level 2, costs 100 coins and makes 1 coin a second, and its Tap Charge ability makes a tap worth 10 times as much every 30 seconds, sooner the more Bullfrogs you own. Our Frog Pond tips for beginners explain why it’s the best early buy. The game’s other tiers include tree frogs, glass frogs and poison dart frogs.
Frequently asked questions #
What is the biggest frog in North America? #
The American bullfrog is the largest true frog in North America. Adults usually measure 9 to 15 cm in body length and can weigh up to 500 g, occasionally more.
Do bullfrogs eat other frogs? #
Yes. Bullfrogs eat other frog species and even smaller bullfrogs, along with crayfish, snakes, rodents, birds and invertebrates.
How can you tell a male bullfrog from a female? #
Look at the round eardrum behind the eye. On males, it’s larger than the eye. On females, it’s about the same size.
Why do bullfrogs croak at night? #
Males call during the breeding season to attract females and claim a spot. Summer nights are when you’ll hear the bull-like bellow most.