History and origin
The Pyrenean brook newt was first described by Dugès in 1852, the scientific name of this species is Calotriton asper, formally Euproctus asper. Euproctus is from Greek and is composed of two words, the first means 'true' and the second means 'behind', this name was given because of their prominent cloacae. Asper comes from latin and means 'rough', their skin is very rough. The new name Calotriton is of unknown origin.

Characteristics
They are characterised by their general unique appearance, a very long squared head, warty skin...

Description
=Size=
- Eggs: The eggs are about 2 to 3 mm in diameter, laid in individual balls of about 4 to 6 mm in diameter.
- Larva: The larva measure about 11 to 12 mm long.
- Juveniles: The young measure between 50 to 55 mm long. (specimens over 2300 m in altitude may metamorphose at 60 mm long).
- Adults: They measure between 100 to 160 mm long (max. : 170 mm long).
=Morphology=
- Eggs: The eggs are laid individual balls fixed on rocks underwater. 10 to 40 eggs are laid.
- Larva: They look like adults but have a longer rectangular head and external gills.
- Adults: They are quite svelte and flattened in appearance, their tail is almost as long as their body and is square in form for the two thirds, the tail finishes in a flattened form. They have short limbs. Their skin is very ripely and they have a multitude of small opening from which can be excreted a liquid substance (se 'defensive habits'). They lack paratoid glands. Their pupils are horizontal.
=Patterns & colours=
- Eggs: They are encased in a transparent envelope, the larva can be seen inside, they are light, sometimes white, their eyes and veins can also been seen.
- Larva: They are light coloured, their tail being generally darker, their external gills are reddish. They become darker as they grow. They have a very short crest on the tail which is very light in colour.
- Adult: They are generally dark, colours being either orange, brown, gray... They usually have a light line type of pattern along the top of the back, this is sometimes broken up into several smaller lines. Their belly is orange.

Geographical range
This species is only found in the Pyrenees.

Subspecies
None described.

Sexual differences
Males have a rounded cloacae. Males limbs are more robust, they also have a shorter tail. Males underside is more vividly coloured then females.

Seasonal variations
Their skin becomes more rough and they become darker during the land phase.

Diet
They feed on fly larva, mosquitoes, may feed on Rana tempoaria tadpoles. The larva eat crustaceans, they may become cannibalistic.

Defensive habits
They will hide under stones in the water if disturbed.

Reproduction
The breeding season starts just after hibernation when the specimens first enter the water, for this the water must be heated around at least 8 C, sometimes as low as 5 C. The male finds a female and he shows off his brightly coloured tail underside. He then jumps onto the female's back and with the help of his hind feet he touches the reproductive parts of the female, this exciting both male and female. He then releases a small amount of sperm which he inserts into the female with the use of his hind feet. This may last for hours. The two mating specimens may be interrupted by an aggressive third specimen. The female lays between 10 to 40 eggs a few days later (Max. a week later), these eggs are laid in caves, crevices and on any covered rock surface.

Sexual maturity, life span
The average life span for Calotriton asper is about 20 years, they reach their sexual maturity in about three years for males and four years for females.

Habits
They are active by day and by night but is only seen on land at dust or night. They are often found when turning stones at the waters edge. Ideal water temperatures to observe this species is around 7 to 10 C.

Habitat
They live from 140 to 2500 m in altitude, however more common at over 1000 m. They live in fresh mountainous streams, avoiding fish occupied waters. They are sometimes found in caves underground (Grotte du Siech - Ariège (09)). Terrestrial habitat is composed of wood covered land, humid forests and rocky areas.

Predators
Trout are their main enemy, however they are also eaten by dragonflies and water insects.