Toads are interesting creatures that live part of their lives on land and part in water. These amphibians are great swimmers and typically migrate to ponds during the breeding season. But how long can toads stay underwater?
Generally, toads can stay underwater for 15 to 30 minutes before returning to the surface for air. However, activity levels will affect the length of time a toad can stay underwater. A resting toad can stay underwater for much longer than an active toad.
Other factors that influence how long a toad can stay underwater include the species, water temperature, and the oxygen content of the water.
Toad Tadpoles Can Stay Underwater for an Unlimited Time
Most toads start their lives as tiny tadpoles. Tadpoles are very different from adult toads because they’re adapted for a fully aquatic life (life in the water), while adult toads are adapted for a mostly terrestrial life.
Toad tadpoles have gills on either side of their head, and a flat paddle-like tail fin to help them move in the water.
At this stage, toad tadpoles breathe underwater through their gills, just like fish.
Their gills have an extensive capillary network very close to the skin surface; Oxygen that is dissolved in the water that comes in contact with their gills is absorbed into their bloodstream via diffusion.
At the same time, carbon dioxide from the bloodstream passes through the gills and is diffused into the water. This gaseous exchange allows them to stay underwater almost indefinitely.
Sometimes, Toad Tadpoles Breathe Air
Tadpoles sometimes live in water with low oxygen levels – where their gills (and skin) cannot absorb sufficient oxygen. This means they also need to breathe air. For this reason, most toad tadpole species also develop lungs in addition to their gills.
When they first hatch, the tadpoles are too feeble to break through the water’s surface for a gulp of air. 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.
Since the tadpoles are tiny, they usually cannot absorb the entire air bubble, and the excess is burped out as a small bubble, after which it 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.
Tadpoles Transform Into Toadlets
After a period of 2 to 3 weeks to as long as over 3 months (depending on the species), the tadpoles go through a process known as metamorphosis. In this process, they lose the features that help them live in the water and develop features more suitable for living on land.
During this process;
- They lose their gills and get well-developed lungs for breathing air
- The tail shortens and is eventually absorbed into the body
- They develop strong legs for moving on land
Once this process is complete, tiny toadlets (small toads), typically half an inch long will leave the water and live a fully terrestrial life.
These toadlets will grow into adult toads and once they mature, they will go back to the water to breed and lay their eggs.
Adult Toads Can Only Stay Underwater for a Limited Time
Unlike tadpoles, adult toads do not have gills. They breathe using their lungs and by absorbing oxygen through their skin.
While underwater, they can not breathe with their lungs, so they have to hold their breath and breathe entirely through their skin (cutaneous respiration).
Dissolved oxygen in the water that comes in contact with their skin is diffused into their bloodstream, and carbon dioxide is released from the bloodstream into the water.
However, this method of breathing usually does not give toads all the oxygen they need, so they can only be submerged for a limited time before they have to resurface to breathe air with their lungs.
How Long a Toad Can Stay Underwater Is Mainly Dependent on 4 Factors
How long a toad can stay underwater is mainly dependent on 4 factors, namely: how much dissolved oxygen there is in the water, the temperature, the toad species, and how active the toad is.
Depending on these factors, most toads can stay underwater from a few minutes to several hours at a time.
1. How Much Dissolved Oxygen Is in the Water
Toads can stay submerged in water with a high oxygen content for much longer than they can in water with a low oxygen content. The oxygen content of the water is affected by several factors including the following:
- The Nature of the Water
Oxygen from the air is dissolved in water at its surface, mostly through turbulence (for example waves, riffles, water tumbling over rocks, etc). For this reason, fast-moving water (such as a stream) will have a higher oxygen content than stagnant 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 Plants 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.
- 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.
- 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.
- 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).
2. Temperature
Like all amphibians, toads are cold-blooded (ectothermic) animals.
This means they cannot internally regulate their body temperature. Instead, their body temperature changes with the temperature in their surroundings.
In other, their environment is the main influence on their body temperature.
For example, a toad swimming in 30°C (86°F) water has a body temperature very close to 30°C. In water at 15°C (59°F), the body temperature of the same toad is around 15°C.
Being ectothermic means toads will have a varied rate of metabolism, depending on the water temperature.
Warmer water temperatures increase metabolic rates. This means toads have to resurface more often to get oxygen.
On the opposite end, cooler water allows toads to conserve oxygen. This extends the time they can hold their breath.
All this combined means toads can stay underwater at lower temperatures for much longer than they can at warmer temperatures.
3. Species
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 toad species are more adept at holding their breath than others and thus can stay underwater longer.
4. How Active the Toad Is
Activity affects how much oxygen the body needs.
Think about it. When you are running or jogging, you breathe in much quicker breaths than when you are lying on the couch.
For toads, this is also true. Their oxygen demands will be influenced by their activity levels.
A toad that is resting on the bottom of the water may be able to stay submerged for several hours.
On the other hand, an individual of the same species who is escaping a predator may only be able to stay underwater for a few minutes before needing to surface to replenish its oxygen supply.
Can Toads Drown?
Even with their ability to breathe underwater through their skin, toads can drown. Toads have lungs, and If their lungs fill with water, they can drown.
The oxygen they absorb through their skin is usually not enough to meet all their oxygen needs for long, so they can only stay submerged for a limited time before they will have to surface to breathe air with their lungs.
If a toad dives into the water so deep that it can not surface for air in time, it will drown.
Conclusion
Toads are semi-aquatic animals, which means they spend part of their lives on land, and part in the water. They start their lives as tadpoles with gills for breathing underwater. At this stage of their life, frogs (tadpoles) can stay underwater for as long as they can get enough oxygen through their gills.
Over time, the tadpoles will transform into toadlets through the process of metamorphosis. During this process, they lose their gills and develop functional lungs.
Once fully transformed, the toadlets will leave the water for life on land. Adult toads breathe by using their lungs and absorbing oxygen through their skin and thin membranes in their mouths and throats.
When underwater, they breathe entirely by absorbing dissolved oxygen in the water through their skin.
This does usually not meet all their oxygen requirements, so they can only stay underwater for a limited amount of time before they have to surface to breathe.