Most people know that frogs that love to hang around ponds and other water bodies are very efficient swimmers. But have you ever wondered if frogs can drown?
Frogs have lungs, and If their lungs fill with water, they can drown. Although they can breathe underwater through their skin, the oxygen they absorb from the water is usually not sufficient, so they can only stay submerged for a limited time before they will have to surface to breathe air with their lungs.
If a frog gets into water where it can not surface for air, or otherwise get out of the water, it will drown.
That being said, it is important to note that many factors will affect whether or not a frog will drown. Some of these factors include, how much dissolved oxygen there is in the water, the temperature, the frog species, and how active the frog is.
Frog Tadpoles Can Not Drown (Usually)
Most frogs start their lives as fully aquatic tadpoles that are highly adapted for their life in the water.
Tadpoles have external gills and a flat paddle-like tail fin to help them swim in the water. They use their gills to breathe underwater, just like fish.
The gills have thin membranes and a network of blood vessels. These membranes absorb dissolved oxygen from the water and move it into the bloodstream.
At the same time, carbon dioxide from the bloodstream passes out through the membranes, and into the water. This gaseous exchange allows them to stay underwater almost indefinitely.
However, sometimes frogs lay eggs in water with low levels of dissolved oxygen – and when the tadpoles hatch, so they cannot get all the oxygen they need by absorbing it from the water.
If tadpoles are in water with a low oxygen content with no way of getting any extra oxygen, they can drown.
For this reason, most tadpole species also develop lungs in addition to their gills. To breathe air with their lungs, tadpoles need to break through the water’s surface to get a gulp of air.
When they first hatch, the tadpoles are too feeble to break through the water’s surface. To get around this, they “bubble-suck”.
To do this, they first stick their open mouths to the underside of the water’s surface. They then open their jaws wide and suck at the water’s surface. Doing this creates an air pocket that they can pinch off by quickly closing their jaws.
After they close their mouth, a portion of the fresh air bubble is forced down into their lungs. The excess air is then burped out as a small bubble that floats back up to the water’s surface.
Once the tadpoles get bigger, they will be strong enough to break through the water’s surface for a gulp of air.
Adult Frogs Can Absorb Oxygen From the Water
After a few weeks months, to a few months (depending on the species), the tadpoles will go through a process known as metamorphosis and transform into adults.
During this process, they will lose their gills, and tails, and develop limbs for walking on land.
Once fully transformed, tiny frogs typically less than an inch long will leave the water and live on land. These tiny frogs will grow into adults and once they mature, they will go back to the water to breed and lay their eggs.
Adult frogs have well-developed lungs which they use to breathe air. They take air through their nostrils, and down into their lungs.
Apart from breathing using their lungs, frogs also can breathe through their skin and thin membranes in their mouth and throat to get extra oxygen.
Their skin contains thousands of capillaries and other blood vessels very close to the skin’s surface. The oxygen that comes in contact with their skin and membranes is absorbed into the bloodstream via diffusion.
At the same time, carbon dioxide from the bloodstream passes through the skin and membranes and is diffused into the atmosphere.
This process of “skin breathing” is known as cutaneous respiration (sometimes informally called “skin breathing”), and is very similar to the gaseous exchange that happens inside our lungs.
How Frogs Breathe Underwater
When underwater frogs can breathe using their lungs. Instead, they breathe underwater by absorbing oxygen that comes in contact with their skin.
Dissolved oxygen in the water that comes in contact with this skin is absorbed into the bloodstream via diffusion. At the same time, carbon dioxide from the bloodstream passes through the skin and is diffused into the water.
However, this method of breathing does not give most frogs all the oxygen they need, so they can only be underwater for a limited time before they have to resurface for a gulp of air.
How Long Can a Frog Stay Submerged Before Drowning?
How long a frog can stay underwater before drowning is mainly dependent on 4 factors, namely: how much dissolved oxygen there is in the water, the temperature, the frog species, and how active the frog is.
Depending on these factors, most frogs can stay underwater from a few minutes up to several hours at a time.
1. The Levels of Dissolved Oxygen in the Water
Frogs can stay submerged in water with a high oxygen content for much longer than they can in water with low oxygen content. The oxygen content of the water is affected by several factors including the following:
- Water Movement
Oxygen from the air is dissolved in water at its surface, mostly through turbulence (for example wave action, riffles, water tumbling over rocks, etc).
For this reason, rapidly moving water, such as in a mountain stream or large river, tends to contain a lot of dissolved oxygen, than stagnant or still water.
If water is very stagnant, oxygen only dissolves on the water’s surface, and anything below the upper layer of the water will have a low oxygen content.
- Presence or Absence of Aquatic vegetation and Algae
Aquatic plants and algae also affect how dissolved oxygen is in a body of water. During the daylight hours, they produce oxygen through photosynthesis and release it into the water.
At night, aquatic plants and algae will use up dissolved oxygen in the water via aerobic respiration and release carbon dioxide into the water.
For these reasons, the concentrations of dissolved oxygen in water with lots of photosynthesizing aquatic vegetation will be highest in the mid-to-late afternoon when photosynthesis rates are greatest, and will reach the lowest concentrations just before the sun rises the next morning.
This fluctuation in dissolved oxygen concentration is referred to as the “diurnal oxygen cycle”.
- How Much Dead Matter /Waste Is the Water
Water with lots of decaying plants and other organic matter (Sewage, yard waste, etc) will have a lower oxygen content.
This is because the bacteria responsible for the process of decomposition use oxygen and release carbon dioxide into the water, reducing the oxygen content of the water.
For this reason, excessive algae and submerged plant growth can also hurt the oxygen content of the water.
As the plants and algae die and decompose, the process consumes dissolved oxygen and releases carbon dioxide into the water.
- The Concentration of Dissolved Salts Present in the Water (Salinity)
Water with a high mineral content (high salinity) can hold less dissolved oxygen than water with a low mineral content (low salinity).
This is due to the more effective competition of the salts for inter-molecular spaces due to their ionic charges. So there is less available space between water molecules for oxygen molecules to occupy.
- Altitude/Atmospheric Pressure
Water at lower altitudes can hold more dissolved oxygen than water at higher altitudes. With rising altitude, the atmospheric pressure decreases – hence less oxygen can dissolve into water.
For this reason water at higher altitudes typically has less dissolved oxygen than water at lower altitudes
2. Temperature
Frogs and other amphibians are ectothermic (cold-blooded) animals, so the environmental temperatures will affect their rate of metabolism. At higher temperatures, they will have a higher metabolic rate, meaning they have a greater oxygen demand
At lower temperatures, the opposite is true. Frogs will have a lower metabolic rate meaning they have a lower oxygen demand.
Also, the temperature will affect the oxygen content of the water. Cool water can hold more dissolved oxygen than warm water.
Higher water temperatures result in increased molecular vibrations, essentially reducing the amount of space available between water molecules – for oxygen to occupy.
All this combined means frogs can stay submerged in cool water for much longer than they can in warm water.
3. Frog species/Skin Surface Area
Tadpoles have gills that provide a very large surface area to absorb lots of oxygen from the water. However, as adults, frogs do not have gills, so how much oxygen they can absorb from the water depends on their skin surface area.
Some frog species have a very large skin surface area and are better at absorbing oxygen from the water than others.
For example, the Titicaca water frog is an aquatic frog species with wrinkled skin. This frog’s excessive amount of skin makes it look rather as if it were wearing an oversized wet suit. But the excess skin performs a very important function – it increases the surface area through which gases can be exchanged.
In fact, the skin is so well adapted for cutaneous respiration that Titicaca water frogs do not have to breathe using their lungs at all! The folds on the skin essentially act as “gills,”.
For this reason, these frogs can live in water with a low oxygen content where most frogs wouldn’t make it. They have even been recorded diving to a depth of 400 feet!
Because of their large skin surface area and very efficient cutaneous respiration, Titicaca water frogs do not need to surface regularly to breathe and can stay submerged for several days without drowning, especially in water with a high oxygen content.
Still, if they are water with a low oxygen content, they will have to surface to breathe oxygen from the atmosphere, or they will drown.
4. How Active the Frog Is
Activity affects how much oxygen the body needs. Think about it, when we are running or jogging, we breathe heavier and in much quicker breaths than when we are at rest.
For frogs, this is also true. They will have a higher oxygen demand when they are very active in the water (escaping a predator or chasing prey, for example), and a lower oxygen demand when they are inactive.
For this reason, inactive frogs will be able to underwater without drowning, for much longer than active frogs.
Some Frogs Stay Underwater All Winter Long Without Drowning
During the winter, frogs go into a state of hibernation/brumation to protect themselves from freezing temperatures.
Frogs that spend most of their time on land will hibernate in burrows below the frost line, inside deep cracks in rocks or logs, under thick leaf litter, and in compost heaps.
Frogs that spend most of their time in or near water (such as leopard frogs and American bullfrogs) will typically hibernate underwater.
However, not just any pond will do, the pond needs to be deep enough so it does not freeze all the to the bottom. It also needs to have lots of dissolved oxygen so the frog can efficiently breathe underwater all winter long.
Unlike most other animals, frogs do not burrow down into the mud when they hibernate underwater.
This is because when underwater, frogs breathe entirely by absorbing oxygen that comes in contact with their skin. So if their skin is buried in mud, their breathing is obstructed and suffocation is a real possibility.
Hibernating frogs can stay underwater all winter long without drowning because they have very low oxygen demands – which can be met entirely through cutaneous respiration.
However, in severe winters when ponds are completely frozen for a long time; hibernating frogs can suffocate and drown when aquatic vegetation starts to die and decompose – reducing the oxygen levels in the water. This is known as “winterkill.”
Some Frogs Are Almost Fully Aquatic
Some species of frogs spend nearly their whole lives underwater. The African Clawed Frog and Green Puddle Frog are just two examples of frog species that rarely leave the water.
These frogs are highly adapted for life in the water and can stay submerged for a very significant amount of time, especially in water with a high oxygen content.
Frequently Asked Questions (FAQS)
Can frogs drown in a swimming pool? Yes, frogs can drown in a swimming pool. Frogs have very absorbent skins, so chlorine and other chemicals found in pools can penetrate their skin and seriously harm or even kill them. Even if a frog is removed from a swimming pool, it can still die if it stayed in the pool long enough for pool chemicals to be absorbed through its skin.
The best thing to do is to prevent frogs from falling into your pool in the first place. You can do this by laying wooden boards at least a foot high around your pool to create barriers. This barrier will act as a ‘wall’ and prevent frogs or other amphibians from falling into your pool.
Still, some frogs may be able to pass through this barrier. So you can set up an escape ramp to help any amphibians that fall to get out on their own.
Can frogs drown in a pond? Frogs can drown in a pond if they fall in and have no way of getting out of the water.
Falling into a pond without chlorine or any other chemicals in the water will usually not be of much harm as long as the frog can get out of the pond. But frogs will drown much quicker if the water in the pond has chlorine or other chemicals.
Do dead frogs float? Dead frogs float, usually with their bellies up because the build-up of gases due to decomposition makes them more buoyant.
Conclusion
Frogs are semi-aquatic animals, which means they spend part of their lives on land, and part in the water.
When in the water, they breathe by absorbing dissolved oxygen in the water through their skin. However, this method of breathing does not give most frogs all the oxygen they need so they can only stay submerged for a limited time before they have to resurface to breathe air with their lungs.
Some frogs hibernate underwater and stay submerged underwater all winter long due to their very low oxygen requirements.
Photo credit: Sandy Sarsfield/Flickr.