Many people know that newts love to spend a lot of their time in streams, ponds, and other water bodies. During the winter, they will sometimes even hibernate at the very bottom of ponds to protect themselves from the frost. But how long can newts stay underwater?
Newt larvae (baby newts) have gills and can stay underwater indefinitely. As adults, newts lose their gills and can only stay for a limited time. Depending on several factors, they can stay underwater from a few minutes to over 8 hours. However, during hibernation, they can stay underwater all winter long.
Adult newts breathe underwater through their skin, so exactly how long they can stay submerged depends on how much oxygen they need vs how much oxygen they absorb from the water through their skin.
This is affected by many factors including the temperature and how much dissolved oxygen is in the water (more information on that below).
Newt Larvae Can Stay Underwater for an Unlimited Time
Newts start their lives as tiny aquatic larvae, that look somewhat similar to frog tadpoles. These larvae have external feathery gills and a flat paddle-like tail fin for life in the water.
At this stage, baby newts (larvae) use their gills to breathe underwater, just like fish.
The larvae gills have thin membranes and a network of blood vessels. These membranes absorb 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 method of breathing gives’ newt larvae all the oxygen they need so they can stay underwater for an unlimited amount of time.
In fact, at this stage, they can not breathe air from the atmosphere, so if taken out of the water for too long, they can suffocate and die.
Larvae Turn Into Juveniles
After a few months, the larvae go through a process known as metamorphosis, in which they lose the features that help them live in the water, and develop features for a life on land.
During this process,
- Their gills are absorbed into their head, and they develop lungs for breathing air
- They develop strong legs for walking on land
- Their flat tail becomes more rounded
Once they are fully metamorphosed, they can live on land and use their lungs to breathe air. However, their lungs are quite primitive and inefficient when compared to our own. For this reason, they also breathe through their skin to get extra oxygen. This is known as cutaneous respiration.
When in the water, they can not use their lungs to breathe air so they breathe entirely through their skin. 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.
This is very similar to the gaseous exchange that happens in the gills of the larvae. However, this method of breathing usually does not give adult newts all the oxygen they need, so they can only be underwater for a limited time before they have to resurface to get oxygen from the atmosphere.
How Long a Newt Can Stay Underwater Is Mainly Dependent on 4 Factors
1. How Much Dissolved Oxygen Is in the Water
Fast-moving or ‘stirred up’ water generally contains more oxygen than still water. This is because oxygen from the atmosphere mixes with the water easier.
If water is very still, oxygen only dissolves on the water’s surface, and anything below the upper layer of the water will have a low oxygen content.
In addition, water with lots of decaying plants 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.
Newts can stay submerged in water with a high oxygen content for much longer than they can in water with low oxygen content.
2. Temperature
Newts 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. Newts will have a lower metabolic rate meaning they have a lower oxygen demand.
Also, the temperature will affect the oxygen content of the water. More oxygen will dissolve into the water at colder temperatures, than at warmer temperatures.
All this combined means newts can stay underwater at lower temperatures for much longer than they can at warmer temperatures.
3. Species
As larvae, the feathers on their gills provide a very large surface area, so newt larvae can absorb all the oxygen they need through their gills. However, as adults, how much oxygen they can absorb from the water depends on their skin surface area.
Some newt species have a larger skin surface area and are better at absorbing oxygen from the water than others.
For example, in crested newts, that large crest provides an extra surface of the skin, enabling them to absorb more oxygen from the water.
4. How Active the Newt 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 newts, 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, newts will be able to underwater when at rest, for much longer than they can when they are very active.
During hibernation, some newt species can get all the oxygen they need through cutaneous respiration, allowing them to stay underwater all winter long.
Can Newts Drown?
Even with their ability to breathe underwater, newts can drown if they are prevented from surfacing for air. Newts have lungs, just like we humans do. If their lungs fill with water, they can drown.
You might think: but newts can through their skin, right? Yes, they can! But this alone usually isn’t enough and they need to surface for air to get extra oxygen.
If a newt gets into a body of water so deep that it can not surface or get out of the water, it will drown.
Some Newts Are Highly Aquatic
Some newts such as the Spanish ribbed newt and the paddle tail newt are highly aquatic their whole life, and very rarely leave the water (although they can walk on land).
They will spend most of their time submerged in standing water they can find, including ponds, lagoons, and damns. If their water dries up, they will hide under rocks or in crevices, anywhere they can stay moist.
Sometimes, Adult Newts Have Gills
Sometimes, newts mature into adults while still in their larval form, without first going through the process of metamorphosis.
This is known as “neoteny”.
Neotenic adult newts look almost like really large larvae. They keep their external gills, flat fan-like tails, and other larval features. They also live entirely in the water, just like the larvae.
Neoteny usually happens when the conditions on land are particularly harsh (such as excessively cold, or dry), making it necessary for the larvae to remain in the water.
Naturally, neotenic adult newts can say submerged for an unlimited time just like the larvae.
Final Thoughts
Newts are semi-aquatic animals, which means they spend part of their lives on land, and part in the water. They start their lives as aquatic larvae and have gills for breathing underwater. As they transform into adults, they lose their gills and leave the water for a life on land.
On land, they breathe by using their lungs and absorbing oxygen through their skin.
Underwater, they breathe entirely by absorbing the 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.
However, during hibernation, they have extremely low oxygen requirements which can easily be met through cutaneous respiration (breathing through the skin), enabling them to stay submerged all winter long.
