Frogs are amphibians, which means they live part of their lives in water and part on land. But can all frogs swim?
In general, the overwhelming majority of frog species can swim, they have webbed feet and powerful hind legs for propulsion. However, some frog species such as the rain frogs of Southern Africa are entirely terrestrial, and can not swim.
Most frogs start their lives in the water and typically go back to the water to mate and lay their eggs. For this reason, they are natural-born swimmers.
Most Frogs Can Swim
The vast majority of frogs are well-adapted for swimming.
They have extensive webbing between their toes, streamlined bodies, and powerful hind legs to propel themselves through the water.
When a frog kicks its legs in unison, it generates a forward thrust that propels it through the water.
Swimming is a less demanding form of movement than jumping. There are also usually fewer obstacles to movement in the water, compared to on land.
Frogs have a universal joint at the knee to enable significant internal rotation of the knee joint.
This rotational degree of freedom means that frogs can align their legs for a very strong kick.
By drawing their legs directly to the body and thrusting the legs directly behind them, frogs are able to generate significant force to propel themselves through the water.
The webbed feet act as the main propulsive unit, pushing large volumes of water behind. This creates thrust and propels the frog’s streamlined body forward.
Some Frogs Can Swim Better Than Others
Although most frog species can swim, some species are more adapted for swimming than others. In general, highly aquatic frogs tend to be stronger swimmers than frogs that are primarily adapted for a terrestrial lifestyle.
For example, Tree frogs generally have small light bodies that allow them to sit on leaves and cling to weak branches without falling. They also have long toes that allow them to wrap around small branches.
As efficient as these features are for climbing, they are not very good for swimming.
Aquatic frogs generally have fully webbed footing and strong powerful hind legs for propelling the frog when in the water.
Since tree frogs lack these features, they are weaker swimmer than most aquatic frogs.
4 Reasons Why Frogs Can Swim
1. Most Frogs Start Their Lives in the Water
Most frogs eggs in shallow ponds, seasonal pools, or other shallow water bodies that are free of fish. Some species such as the red-eyed tree frog lay their eggs on leaves hanging over ponds.
Others such as bromeliad tree frog or Amazon milk frog lay their eggs in puddles that collect in the holes of trees, and water-holding plants such as bromeliads.
After a few days, to a few weeks, tiny tadpoles hatch from these eggs. Tadpoles are very different from adult frogs frogs; this is because they’re adapted for a fully aquatic life (life in the water), while adult frogs are adapted for a mostly terrestrial, or semi-aquatic life.
Tadpoles have external gills and a flat paddle-like tail fin for life in the water. They use their gills to breathe underwater, just like fish.
After a few weeks, these tadpoles will go through a process known as metamorphosis and transform into miniature frogs that live on land.
Once this process is complete, tiny froglets (small frogs), typically half an inch long will leave the water and live a terrestrial life.
Over time, these froglets will grow into mature frogs.
2. Adult Frogs Reproduce in Water
Adult frogs of most species require water to reproduce
During the wet season, frogs will migrate to ponds and other bodies where they can lay their eggs.
On the first warm, rainy night of spring, it’s common to see hundreds of frogs, and other amphibians migrating to wetlands.
This mass migration is often referred to as “the big night”.
In some towns, people close roads and gather to watch thousands of frogs and salamanders on their breeding migration.
During this migration, frogs can travel significant distances, sometimes up to half a mile.
Since frogs breed in the water, their ability to swim is essential for their reproduction.
3. Frogs Re-Hydrate in Water
Like every animal, frogs need to drink water to survive.
That said, Frogs do not drink water through their mouths like we do. Instead, they rehydrate by absorbing water across their permeable skin, in a process known as ‘cutaneous absorption’.
Although most of a frogs’ skin is permeable to water, many frogs have a specialized area of skin located on their belly and the underside of their thighs (the ventral pelvic region), known as the ‘drink patch’, ‘drinking patch’, or the ‘seat patch’. This area of skin is responsible for most of their water uptake.
Frogs generally seek out bodies of fresh water in which they can soak and lie – to rehydrate.
Many frogs love to hang around ponds and other freshwater bodies where they can rehydrate, and keep their skins moist.
In rainy weather, it’s common for frogs to come of out their retreats, and soak in rain puddles on the ground. While they soak in water, they absorb some of the water through their skin and rehydrate.
The ability to swim helps frogs easily soak in water bodies where they can rehydrate.
4. General Locomotion
Swimming enables frogs to easily cross water obstacles in their environments, as they move from one place to another.
Some Frogs Can Not Swim
Although most frogs can swim some frogs cannot swim.
Frogs such as the Common Rain Frogs (Breviceps adspersus) found in southern Africa are entirely terrestrial.
These frogs are not able to swim, or even jump.
They have a round body, and short arms and move by either walking or running.
Common rain frogs are excellent burrowers, and spend most of their time underground, using only emerging during the wet season.
In general frogs toads that live in environments with low availability of surface water are often not adapted for swimming.
Sources:
Fan Jizhuang, Zhang Wei, Yuan Bowen, Liu Gangfeng; Propulsive efficiency of frog swimming with different feet and swimming patterns. Biol Open 15 April 2017; 6 (4): 503–510. doi: https://doi.org/10.1242/bio.022913