Do Frogs Mate With Fish?

Frogs are amphibians, meaning that they are born in water but can also live on land as adults. Therefore, frogs may interact significantly with other aquatic species such as fish. After explaining frog reproduction to other people, I often get the question if frogs can mate with fish. It’s not a crazy question, and you may be surprised by the answer.

Frogs and fish do not mate together and could not have viable offspring. Depending on their size, frogs and fish are each other’s predators. Frogs may grab fish in amplexus during mating season in an attempt to find a suitable female of the same species.

Frogs and fish do not reproduce together and if they did they would probably not have viable offspring. So why do you sometimes see a frog clasping a fish as if it wants to mate with it?

Let me explain this strange, yet explainable phenomenon.

Frogs And Fish Are Each Other’s Predators

Depending on their size, frogs and fish are each other’s predators. Large frogs eat smaller fish, and large fish eat smaller frogs. Frog tadpoles and fish guppies are also known to feed on each other’s eggs.

Big game fish including snook, redfish, pike, catfish, walleye, smallmouth bass, largemouth bass, spotted bass, and muskellunge eat frogs. Fishermen often use plastic frogs as lures or top-water bait to attract and catch these kinds of fish. Smaller fish such as Koi, Goldish, and other bettas also eat frog eggs (CTNF).

Despite frogs and fish sometimes living in the same aquatic habitat, they do not enjoy each other’s company. Most of the time, their relationship is hostile, and they may end up eating each other. Overall, small fish tend to avoid large frogs, and small frogs tend to avoid large fish.

Usually, the bigger species will have the upper hand if they confront each other. Fish are also a well-known predator for frogs to avoid when it comes to eating their eggs. Predation is one of the main reasons frogs lay so many eggs in the wild.

Why Do Frogs Sometimes Grab Fish?

During mating season, male frogs may grab anything in amplexus including fish, male frogs, another species, a dead female, inanimate objects, or multiple frogs when there is competition for few suitable females with whom they can reproduce.

Male frogs go through a trial-and-error process looking for females of the same species that have not yet reproduced. I learned this the hard way when I was a kid. I was just hanging out in the yard when my wild pet toad grabbed onto my thumb in an amplexus position.

Although it freaked me out, that does not mean toads want to mate with a human hand. It was a personal hands-on experience (literally) where I learned that toads and frogs may grab onto anything during mating season.

During mating season, male frogs are generally looking for a female of the same species that has not yet reproduced. They cannot always decipher the difference between a female, a male, or even a fish. 

Many scientific studies found that frogs attempt to mate with male frogs, other species, and even inanimate objects. (Simović et al 2014). A frog’s search for a mate is often a trial-and-error endeavor as they “attempt to clasp practically any moving object” (Wells,  1977; Berven, 1981). Therefore, frogs may grab onto fish thinking it is a female of the same species.

“The reproductive strategy for male B. bufo may be to clasp quickly every moving animal of similar size and then determine whether it is a female.”

Mollov et al. 2010

Honestly, I do not understand how some frog species are still around when their main process of finding a suitable mate is clasping anything that is moving close by to them. But frogs have been here since the Dinosaur Era, so even though it has its faults, their process is still working.

Some people have incorrectly stated that frogs are gay because males may clasp other males during mating season. Yet this is just a natural part of the frog’s process in finding a female of the same species that has not yet laid her eggs. Generally, once the male frog moves on once it realizes what it is holding is not a female it can reproduce with.

Therefore, male frogs may be seen riding or latching onto fish. Though this is a rare occurrence, it does happen. This can lead to the fish dying, especially if the frog clasps it by the gills interfering with their breathing.

Most Frogs Generally Avoid Fish

Many frogs chose ponds that contain no fish in order to peacefully reproduce and thrive. This is true for Spring Peeper, Wood Frogs, Green Frogs, and many other frog species.

Most frogs thrive in areas with a steady supply of slow-moving, calm, freshwater with no fish. The vast majority of frog species reproduce in water and many of them enjoy reproducing in ponds, bogs, marshes, or fens. 

If you decide to have a backyard frog pond, it is best to not add fish as they may prey on each other and cause each other stress. The coexistence between fish and frogs in the wild is a delicate balance and can be hard to replicate in your backyard pond (CTNF).

In the future when your frog population has stabilized you may wish to try adding some fish that do not eat frogs like Koi if the pond is large enough and frogs have already laid their eggs. However, in the beginning, you should keep the wildlife in your pond solely focused on frogs.

More About How Frogs Mate

Although you wouldn’t see a fish chasing a frog unless it wants to eat it, you may have seen a frog riding a fish, or clasping a fish in amplexus. It’s not that the frog wants to mate with the fish, the frog is looking for a suitable female of the same species.

Learn more about how frogs reproduce on our blog:

Sources

Berven, K.A. (1981): Mate choice in the wood frog, Rana sylvatica. Evolution 35: 707–722.

Mollov, Ivelin & Popgeorgiev, Georgi & Naumov, Borislav & Tzankov, Nikolay & Stoyanov, Andrey. (2010). Cases of abnormal amplexus in anurans (Amphibia: Anura) from Bulgaria and Greece. Biharean Biologist. 4. 121-125. 

Simović, Aleksandar & Anderson, Nils & Marko, Andjelković & Slađana, Gvozdenović & Nikolić, Sonja. (2014). Unusual amplexus between anurans and caudate. Herpetology Notes. 7. 25-29. 

Wells,  K.D.  (1977): The social behaviour of anuran amphibians. Animal Behaviour 25: 666–693

The Irish Times, My goldfish are assaulted by frogs. Readers’ nature queries, Sat, Apr 25, 2020.