Frogs generally thrive in salt-free freshwater lakes, ponds, marshes, bogs, fens, and other clean sources of freshwater. The vast majority of amphibians have porous skin through which they breathe and drink, and so, unfortunately, saltwater can dehydrate and kill them.
In 2015, scientists Hopkins and Brodie identified 124 frog species able to inhabit saltwater habitats. This number represents less than 2% of over 7,500 known frog species, and more research is needed to understand how frogs are evolving to live in brackish conditions.
Therefore, most frogs cannot safely develop or live in saltwater. However, frogs are extremely adaptable; a few species have evolved to become accustomed to brackish and saline water.
Why Can’t Most Frogs Live in Saltwater?
The vast majority of frogs cannot survive in saltwater. Saltwater disrupts the water exchange and ionic balance across a frog’s permeable skin membrane causing serious dehydration. Less than 2% of known frog species have been observed to have adapted to brackish conditions.
In general, frogs cannot handle high salinity levels in saltwater. Frogs drink and breathe through their skin. A salty environment is dangerous for frogs since water molecules move from the water in which they bask into the frog’s body. If the water is salty, the frog can dry out and die.
Many aquatic frogs have a natural, innate reaction to jump away when they are in contact with any salt. You may observe this if you purchase frog legs and sprinkle salt on them. Even though the legs are not attached to a living frog, they still move and react to the salt.
This is why salt is sometimes used as a frog repellent around people’s yards, swimming pools, and private ponds.
A frog’s skin is naturally adapted to live in clean freshwater. Even though frogs have lungs, aquatic frogs rely on their skin to absorb oxygen. Not only that, but aquatic frog skin is also porous enough to lose moisture quickly.
Seas and oceans have high salinity levels in the water. This is why you will generally not find any frogs on the beach.
The most vulnerable species are aquatic frogs that live in water most of the day, as well as frogs at younger stages of development (eggs and tadpoles) that require celan, freshwater to safely evolve into healthy adult frogs.
Frogs require water to breed. This is why during mating season, both aquatic and terrestrial frogs spend time in the freshwater. However, there are 124 known species of frogs that have adapted to survive in saltwater at all or different stages of their life cycle (CTNF).
124 Frog Species Are Known to Have Developed Saltwater Tolerance
Much like how frogs sleep, very little research has been carried out on frog tolerance and adaptation to saltwater environments.
Since scientists and naturalists began studying amphibians, they have always believed that amphibians cannot tolerate saltwater:
“This general absence of frogs, toads and newts on so many true oceanic islands cannot be accounted for by their physical conditions […]. But as these animals and their spawn are immediately killed […] by sea-water […] we can see why they do not exist on strictly oceanic islands.”Charles Darwin (1872)
In 2015, scientists Hopkins and Brodie identified 144 amphibian species from 28 amphibian families, of which 124 Anura, able to inhabit saltwater habitats (Hopkins et al, 2015).
Here are some of the 124 frog species with known saltwater tolerance:
- Columbia Spotted Frog (Rana luteiventris)
- Lowland Leopard Frog (Lithobates yavapaiensis)
- Southern Leopard Frog (Lithobates sphenocephalus)
- Western Toad (Anaxyrus boreas)
- Pacific Tree Frog (Pseudacris regilla)
- Tiger Frog (Rana pipiens)
- Clawed frog (Xenopus laevis)
- Crab-Eating Frog (Fejervarya cancirvora)
- Berber Toad (Bufonidae Amietophrynus mauritanicus)
- Iberian Painted Toad (Discoglossus galganoi)
- Mediterranean painted frog (Discoglossus pictus)
- Tyrrhenian painted frog (Discoglossus sardus)
- Yellow-Bellied Toad (Bombinatoridae Bombina variegata)
- Cane Toad (Rinella marinus)
- American Bullfrog (Lithobates catesbeianus)
- American Toad (Anaxyrus americanus)
- Natterjack Toads (Epidalea calamita)
- Fowler’s Toad (Anaxyrus fowleri)
- Oak Toad (anaxyrus quercicus)
- Common Toad (Bufo Bufo)
- Southern Toad (Anaxyrus terrestris)
- Spring Peeper (Pseudacris crucifer)
Hopkins et al. (2015) compiled a detailed table of salt-tolerant amphibians based on prior research and observations. The table details where the frogs were found and their lifecycle stage (egg, larvae, adult).
Many of the saltwater tolerant frogs were found in tidal mangroves and swamps, at the beach under driftwood, near coastal marshes, in saline lakes, and in some cases, in the ocean or sea. Salt-tolerant amphibians were found all over the world, except in the Antarctic.
How Did Some Frogs Develop Tolerance to Salt Water?
124 known Anuran species have developed tolerance to brackish conditions at different levels of salinity in part by “urea hypersynthesis and retention and Na⁺ and Cl⁻ uptake to increase the osmolarity of the body fluids and plasma to be isotonic with the surrounding seawater” (Hopkins et al, 2015).
To put this simply, some frogs may have a genetic predisposition to adapt to salt water by altering their physiology. Some frogs also have three glands (vacuolated, mucous, mixed) on their skin that can help create a barrier to prevent salt from entering their body.
Many amphibians that have evolved to tolerate living in salty conditions possess certain glands, membranes or genetic mutations to protect themselves from high salinity levels. Such frogs can efficiently regulate moisture through their skin and effectively retain salts through the exchange of chlorine and sodium ions.
However, understanding how frogs and different species are evolving and adapting to brackish conditions around the world is still under review, debate and study by scientists.
Overall, few homogeneous studies have been carried out to understand how amphibians are adapting to current environmental conditions, and more and more species are being discovered living in saltwater since the early 2000’s.
Frogs have been around since the Dinosaur Age over 200 million years ago and managed to remain active on the planet thanks to one of their greatest strengths: their adaptability.
Although amphibians are not made to live in brackish conditions, some have evolved to be able to deal with environmental degradation, roads that cut off access to their natural habitats, habitat loss, raise in sea levels, pollution, climate change, deforestation and other nefarious human activities (anthropogenic change) which have accelerated in recent years.
Some Frogs Have Evolved to Survive in Difficult Conditions
Frogs are more and more obliged to evolve in stressful environments and adapt to be able to live in saltwater conditions due to nefarious human activity. Although frogs are generally adaptable, this does not excuse the devastating impacts of anthropogenic change.
Some frogs have naturally adapted to thrive in harsh conditions, even before anthropogenic change. Waxy tree frogs live in arid regions with minimal water thanks to the unique membrane on their skin that retains water and prevents evaporation. They are heavily adapted to survive in such environments.
The crab-eating frog has found ways to adapt to its environment and is able to thrive in saltwater with up to 75% seawater. It also thrives just as well in fresh water by quickly changing the urea levels in its body tissues to minimize excessive water loss in saltwater environments.
However, frogs that tolerate some levels of salinity only represent less than 2% of known frogs at the moment. Although more research is required to understand how frogs are evolving to tolerate such stressful environments, the majority of frog and toad species cannot survive in saltwater conditions. Therefore, without action, these frogs will either need to adapt, or will continue to decline in populations.
More About Frogs And Water
Further research is needed to understand how frogs are adapting to brackish conditions based on the species, environment, life cycle stage, and methods (genetic, cutaneous, etc) used to adapt to their evolving habitats.
Learn more about frogs in these guides on our blog:
- Can Frogs Drown?
- Frog Skin: Everything There is to Know
- How Do Frogs Survive?
- Will Tap Water Kill Frogs?
Common Questions About Frogs And Saltwater
Why can’t frogs live in saltwater? In 2015, scientists Hopkins and Brodie identified 124 frog species capable of living in saltwater habitats including Cane Toads, American Bullfrogs, American Toads, Natterjack Toads, Fowler’s Toad, Oak Toads, Common Toads, and Southern Toads.
Why does salt hurt frogs? Saltwater can cause serious dehydration in frogs since frogs drink and breathe by osmosis, directly through their skin. A frog’s skin is porous and saltwater clogs a frog’s pores and dries them out, preventing them from breathing and drinking which can lead to death.
Can frogs survive in saltwater pools? The vast majority, currently 98% of frogs cannot survive in saltwater. Less than 2% of known frog species have been observed to have adapted to brackish conditions.
Do saltwater amphibians exist? At the moment 144 species of amphibians are known to be able to live in saltwater. Since amphibians have needed to adapt to changing environmental conditions due to human activity, more and more frogs, toads, salamanders, newts and caecilians are being discovered surviving in saltwater conditions.
Are there any oceanic amphibians? Of the 144 species of amphibians that are known to be able to live in saltwater, there are 11 documented species that can live in oceanic conditions including Western Toads, Oak Toads, Natterjack Toads, Crab-Eating Toads, Southern Cricket Frogs, Spring Peeper, and Pacific Green Frogs.
Can frogs live in still water? 98.4% of frogs cannot survive in saltwater since most frogs cannot handle low or high salinity levels in saltwater. Frogs drink and breathe through their skin and if the water is too salty, the frog can dry out and die.
What are the frogs that live in water called? Frogs that live in water are generally referred to as “aquatic frogs.” These frogs require water to live but can spend some time on land. However some frog species are referred to as “fully aquatic frogs” and need to constantly be in water to survive.
Gareth R. Hopkins and Edmund D. Brodie “Occurrence of Amphibians in Saline Habitats: A Review and Evolutionary Perspective,” Herpetological Monographs 29(1), 1-27, (1 December 2015). https://doi.org/10.1655/HERPMONOGRAPHS-D-14-00006
Inside Ecology, Frogs and Toads at the Coast Salt Tolerance in Amphibians
AmphibiaWeb, Amphibians by the numbers