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How does a bullfrog tadpole grow into a frog? | Ponds & Lakes Q&A


How does a bullfrog tadpole grow into a frog?

Q: How does a bullfrog tadpole grow into a frog?

Dan – Clovis, CA

A: What would a pond or lake be without bullfrogs? These croaking amphibians – which can grow to 8 inches in length and weigh up to 1½ pounds – reside near water sources, like lakes, ponds, rivers and bogs. The brown-green frogs with the scientific name Lithobates catesbeianus prefer warm, still, shallow water.

Through their seven- to nine-year life cycle, bullfrogs pass through several stages of development. Ever wonder what happens during those stages? Keep reading, because here’s what you need to know.

From Eggs to Tadpoles

Bullfrog breeding, which happens externally, takes place in May to July in the north and from February to October in the south. The female adult bullfrog, which sports a white throat during the mating season, deposits as many as 20,000 eggs in a foamy film in quiet, protected waters; the male, which has a yellow throat during mating rituals, then fertilizes them. Four days later, tiny tadpoles emerge. The little guys are able to fend for themselves right away and will stay in their tadpole stage for almost three years before transforming into adults.

Pollywog Waltz

While they’re in their tadpole – or pollywog – stage, the tiny gilled critters live exclusively in the water and nibble on water plants for nourishment. At first, their bodies, which can measure up to 6¾ inches long, are long and narrow and include a tail where they store fat when food is in short supply during the winter months. After about one year, the tadpoles will start to grow legs. Shortly thereafter, they grow arms. And then, their tails shorten, they develop lungs, and their gills disappear. The tadpoles have transformed into froglets.

From Aquatic to Terrestrial

After that two- to three-year tadpole-to-frog developmental period, the bullfrog ’s final growth stage is when the froglet hops from the water to dry land. Thanks to its fully developed lungs, the now-carnivorous and aggressive frog can now breathe oxygen, and that gives it the freedom to emerge from its watery first home to the shore where it can hunt for anything that will fit in its mouth, including insects, small mammals, birds, fish and other frogs. The adult bullfrog rests by day, and defends and hunts its 3 to 25 meters of shoreline territory by night.

Finally, after three to five long years of growth and development, the tadpole has become an adult bullfrog and reached sexual maturity – and the life cycle begins again. Bullfrogs in the wild live to about 7 to 9 years old; in captivity, they can live as long as 13 years.

Now the next time you hear your bullfrogs croaking, you’ll have a new appreciation for them!

Pond Talk: What’s your favorite part of having bullfrogs in your lake or pond?

13 Responses

  1. Oddly, I unearthed a live tadpole in our koi pond while trying to clean out leaves!!!! And this is in, or below, the low 30 temps at night here in zone 7 in Upstate SC and warming to the mid 50’s to low 60’s in the daytime. I couldn’t believe it and have no idea whether he will survive. We had tens of thousands in the spring and less during the summer but this little guy was wiggling around live as could be!

  2. I read that frogs will travel up to a mile if they like the pond location. Proof was in our taking 8 adults to a pond way behind our house so they would have a safe place to spend the winter and all 8 were back in a couple of days. These little guys, though, were only about 1″ long when they all appeared. A lot of traveling for a bunch of little guys. I love checking on our ‘children’ every day. The are now exploring the lower pond and also lining up on the rock edge around the pond. Have taken many photos. Very entertaining.

  3. WE HAVE A VERY LARGE BULLFROG THAT LIVES AROUND OUR BACKYARD POND. I JUST DONT KNOW WHERE HE DISAPPEARS IN THE WINTER. DO THEY BURY DOWN INTO THE DIRT FOR THE WINTER?

  4. I forgot to mention…some of the ‘froglets’ are brown and some are tinged with a lime green on the bottom half of their bodies.

  5. I once stopped my car to make sure a bullfrog got across the road safely.

    My question is about normal ‘pond’ frogs. We have 12 ‘babies’ but never saw any tadpoles. How can that be? Are all frogs tadpoles first? They certainly are entertaining!

    • They probably came to you originally as adults, as ours did from another pond and creek about a quarter of a mile away. We had the pond empty for a year while deck was built then relined it. So they had to come as adults as I didn’t put them there-LOL

  6. My husband likes them as they give interesting life to out large pond. I hate them! They ate all the fish that I bought and now there are none.

    • It is so funny that you should say this, I have had people tell me that they will eat my Koi, never has this happen ever!! I had to re-locate chipmonks, as they were eating my frogs left and right. But, when day breaks the bullfrogs leave my pool, hop on over to my Koi pond, and rest assured they leave my Koi alone. I feed my Koi, with the frogs on my lilly pads, or off to the side, and they have never yet attempted to cash in on my fish, be advised I live in Southern New Hampshire, on the Massachusetts line. Not sure if that makes a difference

      • Your frogs may currently be getting their meal from an easier source. If it comes down to it, and they need to eat, they will not think twice about eating a koi or bird. I wouldn’t have believed it if I hadn’t seen it with my own eyes, but they can do it.

  7. I love my bullfrogs. I have an inground pool that is next to my fish-koi pond, just when it starts to get dark, I have 3 that sit on the stairs of my pool, and eat all the bugs that land in the night, the results, hardly any bugs in my pool!!!!

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