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Fish are supposed to stay underwater. They have gills, fins, and bodies built for swimming. So what happens when a fish climbs onto land and starts moving around?
It sounds like something from a strange nature documentary, but it is real.
Several fish species can leave the water and move across land. Some can crawl over mud. Others can push themselves across wet ground, climb roots, or travel between ponds. A few can even survive outside water for hours or days when conditions are right.
These animals are often called walking fish, although most don't actually walk like humans or four-legged animals.
So, what fish can walk on land, how do they breathe, and why did they evolve this strange ability? Let's take a closer look.
What Is a Walking Fish?
A walking fish is a fish that can move across land or survive outside water for a significant amount of time.
The term doesn't describe one particular species. Instead, it refers to several unrelated fish that have independently developed unusual ways to deal with life outside water.
Some of the best-known examples include:
- Mudskippers
- Walking catfish
- Snakeheads
- Climbing perch
- Lungfish
These fish don't all move in the same way.
Some use their fins like limbs. Others wriggle their bodies across the ground. Some can breathe air using special organs, while others rely partly on their skin.
This is an important point: there isn't one single way for a fish to survive on land.
Different species have evolved different solutions to similar problems.
Mudskippers: The Fish Most Famous for Walking
If you search for a fish that can walk on land, you're likely to see a mudskipper first.
Mudskippers live around coastal mudflats, mangroves, and estuaries in parts of Africa, Asia, and Australia. Unlike most fish, they spend a large amount of time outside the water.
And they are surprisingly good at it.
How do mudskippers move?
Mudskippers use their strong pectoral fins to push their bodies across mud.
Their fins act almost like small limbs. They can lift part of their body, push against the ground, and move forward in a series of short hops and crawling movements.
They can also climb over rocks, roots, and other surfaces.
This isn't true walking in the same sense as a dog or human walking. But from a distance, a mudskipper moving across mud certainly looks like a fish that has decided to leave the water behind.
How do mudskippers breathe on land?
This is where things become even more unusual.
Mudskippers can absorb oxygen through their skin when it remains moist. They can also exchange gases through the lining of their mouth and throat.
Their gills still matter, but their ability to use other surfaces for gas exchange helps them survive outside water.
The catch is simple:
They must stay moist.
A completely dry mudskipper would not be able to use its skin for breathing effectively.
This is one reason mudskippers are strongly associated with wet mud, puddles, and humid coastal environments.
Walking Catfish Can Travel Across Land
Walking catfish take the idea of a land-traveling fish even further.
Several species in the catfish group known as Clarias can move across land. They are native to parts of Asia and Africa, and some have become invasive in places such as Florida.
Their ability to travel over land can help them move from one body of water to another.
How does a walking catfish move?
A walking catfish doesn't stand up and take steps like a land animal.
Instead, it combines body movements with its strong pectoral fins and spines to push itself forward.
The result looks like a strange mixture of crawling, wriggling, and walking.
On a wet night, a walking catfish can potentially move across surprisingly large areas of land.
How can it breathe outside water?
Walking catfish have specialized air-breathing structures that allow them to take oxygen directly from the atmosphere.
This gives them an advantage when water becomes difficult to live in.
For example, if a pond becomes crowded or conditions become poor, moving to another water source may offer a better chance of survival.
Unfortunately, the same ability can become a problem when these fish enter ecosystems where they don't naturally belong.
In parts of the United States, invasive walking catfish have been reported in drainage systems, ponds, canals, and even swimming pools.
Snakeheads Can Survive for Days Outside Water
Snakeheads are another group of fish famous for their ability to survive on land.
But calling them "walking fish" can be misleading.
Snakeheads don't have legs, and they don't normally walk upright.
Instead, they can use a wriggling, snake-like movement to travel across wet ground.
How do snakeheads breathe air?
Snakeheads have a specialized air-breathing organ that allows them to extract oxygen from the atmosphere.
This adaptation is extremely useful in warm, shallow, or oxygen-poor water.
Under suitable conditions, some snakeheads can survive outside water for several days as long as they remain damp.
Their ability to breathe air and move between waterways has also contributed to concerns about invasive snakehead populations in parts of the United States.
Are snakeheads dangerous?
The biggest concern is usually ecological rather than physical danger to humans.
Some introduced snakehead species can become predators in new environments. They may compete with native fish and other aquatic animals for food and habitat.
This is why wildlife agencies take reports of invasive snakeheads seriously.
How Can a Fish Survive Without Water?
The biggest challenge for a fish on land is not actually movement.
It is breathing and avoiding dehydration.
Water supports the normal function of fish gills. When a typical fish is removed from water, its gill structures can stop working properly as they collapse or dry out.
Walking fish have developed different adaptations that help solve this problem.
Air-breathing organs
Some fish have specialized organs that allow them to take oxygen directly from air.
This can work somewhat like an additional breathing system alongside their gills.
Oxygen-absorbing skin
Certain fish can absorb oxygen through their skin.
But the skin must remain wet for this process to work effectively.
This is particularly important for mudskippers.
Modified fins
Strong, flexible fins can help some fish push their bodies across land.
They aren't the same as the limbs of a mammal, but they can perform some similar mechanical functions.
The ability to tolerate low oxygen
Many of these fish live in environments where oxygen levels can change dramatically.
Shallow mud, warm ponds, swamps, and stagnant water may contain far less dissolved oxygen than a healthy flowing river.
Being able to breathe atmospheric oxygen gives these animals a major advantage.
Why Did Fish Evolve the Ability to Leave Water?
Leaving the water may seem like a dangerous choice for a fish.
But evolution doesn't ask whether something looks strange to us. It favors traits that help organisms survive and reproduce in their particular environment.
Imagine a fish living in a shallow pond.
During a dry season, the pond begins to disappear.
A fish that must remain underwater may become trapped.
But a fish capable of surviving on land could potentially reach another pool.
The same ability might help an animal:
- Escape poor water conditions
- Find new food
- Avoid certain predators
- Move between isolated pools
- Survive droughts
- Find a better habitat
- Take advantage of food available near the water's edge
Over many generations, traits that improve survival can become more common.
This is one reason scientists are interested in modern walking fish.
Did Walking Fish Evolve Into Land Animals?
This is one of the most common misunderstandings about walking fish.
No. Modern walking fish did not simply evolve into today's land animals.
A mudskipper living today isn't a direct ancestor of humans, reptiles, or mammals.
Instead, modern walking fish provide useful examples of how evolution can produce adaptations for life outside water.
The transition from water to land happened hundreds of millions of years ago and involved ancient vertebrates that are now extinct.
Fossils provide important evidence about that transition.
Living animals provide another source of information.
What can scientists learn from them?
Researchers can study animals such as mudskippers to understand how certain abilities work.
For example:
- How fins can produce movement on land
- How fish exchange gases in air
- How bodies cope with dehydration
- How muscles control unusual movements
- How behavior changes between water and land
These studies don't recreate the exact history of evolution.
Instead, they help scientists understand what kinds of biological changes are possible.
The Difference Between Walking, Crawling, and Surviving on Land
Not every fish described as a "walking fish" actually walks.
That's an important distinction.
True limb-like movement
Mudskippers use their fins in a way that resembles walking or crawling.
Body-powered movement
Snakeheads can move across land by bending and pushing their bodies against the ground.
Fin-assisted movement
Walking catfish use their fins, spines, and body movements to move over land.
So when you see a headline saying that a fish can "walk," it is worth asking what the fish is actually doing.
The movement may look like walking, but the anatomy and mechanics can be completely different from those of a land vertebrate.
Why Walking Fish Matter
Walking fish are more than a strange nature fact.
They show how flexible life can be.
A fish doesn't necessarily need to remain completely underwater all the time. With the right adaptations, it can spend part of its life in a completely different environment.
They also show that evolution doesn't always produce a clean divide between one lifestyle and another.
There are animals that live entirely in water.
There are animals that live entirely on land.
And there are species that exist somewhere in between.
Walking fish occupy that fascinating middle ground.
They remind us that nature is full of experiments that have been running for millions of years.
Frequently Asked Questions
What fish can walk on land?
Mudskippers are the most famous fish that can move on land. Walking catfish, some snakeheads, climbing perch, and other air-breathing fish can also move or survive outside water, although their methods are different.
Can fish really walk like humans?
Not usually. Most so-called walking fish crawl, wriggle, hop, or push themselves across the ground using their fins and bodies. Mudskippers come closest to a walking-like movement.
How long can a fish survive on land?
It depends on the species and conditions. Some fish can survive outside water for only a short time, while certain snakeheads and walking catfish can survive for hours or even days under suitable conditions. Moisture, temperature, and access to air all matter.
Can a fish breathe air?
Yes. Some fish have evolved special adaptations that allow them to breathe atmospheric oxygen. Examples include snakeheads, walking catfish, lungfish, and mudskippers.
Why do fish leave the water?
Fish may leave the water to find food, escape poor conditions, avoid predators, move between bodies of water, or survive when their habitat becomes too dry or oxygen-poor.
The idea of a fish walking across land sounds impossible until you see one do it.
Mudskippers use powerful fins to move across mud. Walking catfish can travel between waterways. Snakeheads can breathe air and survive outside water under the right conditions.
None of them are simply "fish turning into land animals." Instead, they represent different evolutionary solutions to the same basic challenge: how to survive when life takes you outside the water.
And that's what makes them so fascinating.
If you want to explore the next step in this story, read our related guide on how ancient fish eventually gave rise to the first land vertebrates and discover what happened during one of evolution's biggest transitions.
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