Amphibians

Disappearance of wetlands, road development, pollution… The amphibians are among the species most vulnerable to human activities!
Adult frog.

Adult frog.

The amphibians themselves are freed of the aquatic environment there are more than 380 million years. Three orders are recognized among current amphibians:
  • The Anurans: toads, frogs and tree frogs;
  • The Urodeles: newts and salamanders;
  • The Gymnophiones (being not present in France they are not developed here).
Amphibians are vertebrates with variable temperature: they regulate their body temperature warming in the Sun or cooling in the shade. They have to start their life in the water and end it on earth. At birth, they breathe through gills like fish, so only adults they have lungs even if they absorb a large part of their oxygen through the skin. Once adult, amphibians will seek a place for reproduction. It is usually an aquatic habitat, which can be found close to the area of earthly life, but may also be several hundred meters away (or even a few kilometers). They will do then several migrations:
  • Migration prenuptial between wintering and breeding sites (usually corresponding to place of birth)
  • The groups migration between breeding sites and the ‘summer quarters”
  • Fall, migration for some species, to wintering sites
Toads reach aquatic habitats at the time of breeding.

Toads reach aquatic habitats at the time of breeding.

Urbanization and the human development (roads in particular) make travel difficult and deadly. Added to the disappearance of wetlands and pollution, these hazards endanger populations of amphibians.

The Anurans: frogs, toads and tree frogs

Anurans include toads and frogs. They are characterized by the absence of tail in adulthood and a short and stocky body. The larva of frog (tadpole) looks very different from the adult, with a disproportionate head, the absence of members and a long tail with fins.
Between hatching and metamorphosis, several transformations will come one after another: training of internal gills, appearance of hind limbs then anterior, disappearance of the tail…

Several elements are used to distinguish the toads, frogs and tree frogs.
The skin, first of all, is different. The frogs are smooth and wet while the toads are dry with growths.
The legs can also be a clue. Frogs have long back legs, in the form of Z that they unfold to jump and move forward. The legs of the toads are smaller and less muscular than those of frogs and toads move crawling or by small jumps. The legs of the tree frogs have adhesive disks at the ends of the fingers, allowing them to climb on trees.
The habitat of the species may also differ. Thus, the frogs are rather aquatic (and can stay under water for a long time) while the toads are more terrestrial and not seeking water except at the time of mating. The tree frogs are arboreal, we often find them in trees or shrubs.
Spawning is also different because frogs lay their eggs in piles, while toads lay in string. However, this difference is not always obvious depending on the species.

Frog habitat is mostly aquatic.

Frog habitat is mostly aquatic.

While toads are rather terrestrial.

While toads are rather terrestrial.

The Urodeles: newts and salamanders

Unlike Anurans, the Urodeles retain their tails to adulthood and their body is more elongated. So the Urodele larvae have the same general form as adults. They have also 3 pairs of external gills.

In the water phase (for reproduction), the tail of newts is highly developed allowing them to swim. In courtship, males also have a dorsal ridge. The parade of newts is a complex aquatic dance and the eggs are deposited on aquatic plants.
In earthly phase, the newts are discreet and nocturnal. They take less bright colors and their tail is undeveloped. We sometimes meet them in a rotten stump, sometimes hidden under a rock or dead leaves.

Salamanders are almost exclusively terrestrial, not regaining the water to lay. Mating takes place on earth, mainly around May and September-October. Gestation can last for several months, before the females join a water point to deposit their larvae.
Salamanders differ from the newts by their tail with circular section. Discrete, the most often nocturnal, they remain hidden under boulders, under stumps or in holes in the ground.