Newts are a group of salamanders that constitute the subfamily Pleurodelinae within the family Salamandridae. They are characterized by lizard-like, slender bodies, covered with moist, glandular skin.
These animals possess the lifelong ability to regenerate lost body parts, with cells at the injury site dedifferentiating, multiplying, and then redifferentiating to replace structures, including limbs, tails, eyes, and even parts of internal organs in some species.
Being amphibians, newts spend most of the non-breeding period on land, returning to water during the breeding season for mating. Females deposit their eggs on aquatic plants, carefully folding leaves around them for protection. The eggs hatch into larvae that later metamorphose into juveniles, known as efts, which live on land before maturing into adults.
More than 100 species of newts are found in North America, Europe, North Africa, and Asia. They are highly sensitive to changes in their surroundings, making them bioindicators of pollution.
These amphibians are typically 3 to 6 in (7 to 14 cm) long. However, some newts of the genus Triturus reach 8 in (20 cm).[1]
Newts have a slender, elongated body with a head, trunk, and long, laterally compressed tail. Their smooth, moist skin is semipermeable and glandular, aiding in gaseous exchange. They typically occur in shades of brown or green, with some species turning orange during the breeding season.
The head is broad and flat, equipped with eyes (having prominent, movable eyelids), paired nostrils, and a wide mouth with small teeth for gripping prey.
The trunk bears two pairs of limbs, which are relatively short and slender compared to the body length. The forelimbs bear four digits, whereas the hindlimbs have five.
The well-developed tail serves as an effective swimming organ, providing propulsive force in water. In contrast to frogs, which shed their tails after metamorphosis, newts retain this feature for life.
The term newt originates from the Old English words efte or efeta. In Middle English, the word became eft. With time, through changes in speech, people started to pronounce an eft as a neft, which eventually became a newt.
Over 100 species of newts are classified into 16 genera.
Based on phylogenetic studies, the subfamily Pleurodelinae most likely originated in Eurasia during the Oligocene to Miocene Period.[2]
North America is home to the Pacific newts (Taricha) and the Eastern newts (Notophthalmus).
Europe and Western Asia support the greatest diversity, with nine genera, including Triturus, Lissotriton, Ichthyosaura, Calotriton, Euproctus, Ommatotriton, and Pleurodeles, among others. Eastern Asia, on the other hand, is home to 5 genera: Cynops, Paramesotriton, Pachytriton, Laotriton, and Tylototriton.
In Africa, newts are represented only by a single genus, Pleurodeles.
As amphibians, newts are semi-aquatic and spend the majority of the year on land, moving into water primarily for breeding. Although most species prefer living in stagnant water bodies, such as ponds, ditches, or flooded meadows, some, such as the Danube newt (Triturus dobrogicus), typically breed in slow-flowing rivers.[3]
A few species, such as the Montseny brook newt (Calotriton arnoldi), are highly specialized for life in cold, fast‐flowing mountain streams, where temperatures generally remain below 59 °F (15 °C) throughout the year.[4]
The diet of newts varies with the different stages of their life cycle. As larvae, they initially feed on small aquatic invertebrates such as planktonic crustaceans (like Daphnia), mosquito larvae, and water fleas. Eventually, as terrestrial efts, they feed on invertebrates such as ants, springtails, tiny beetles, mites, and worms.
When on land, adults consume a range of invertebrates, including earthworms, beetles, caterpillars, spiders, and slugs. However, in water, they feed on larvae of aquatic insects, snails, tadpoles, and small crustaceans.
In some species, such as the northern crested newt (Triturus cristatus), aquatic subadults and non-reproductive adults have been observed feeding on larvae of their own species (canibalism).[5]
These amphibians are generally nocturnal, foraging at night to avoid predators. They move on land with a sprawling gait, but in water, they swim with side-to-side tail movements, using their limbs mainly for steering.
Many species are capable of releasing toxins from their skin to ward off predators. Members of the genus Taricha are particularly toxic. For instance, the rough-skinned newt (Taricha granulosa) produces tetrodotoxin toxic enough to kill an adult human.
Most newts live 6 to 15 years in the wild, but with proper care in captivity, some species, such as the northern crested newt, have been recorded living up to 28 years.[6]
Some individuals of the Japanese fire-bellied newt (Cynops pyrrhogaster) have been recorded living over 47 years in captivity.[7]
They typically breed during the warmer, wetter months of the year, when they migrate from land back to ponds, lakes, or slow-moving streams. The males perform elaborate courtship displays, such as waving their tails, to attract females. Once a pair forms, the male transfers a packet of sperm (spermatophore) on a substrate, from where the female collects it using her cloaca.
After fertilization, the female typically lays 100 to 400 eggs singly on the leaves of aquatic plants. In 2 to 3 weeks, the eggs hatch into larvae with feathery external gills. These larvae remain aquatic for 2 to 5 months, continue to feed, and gradually develop forelegs. Gradually, through metamorphosis, their gills are absorbed, they develop hind legs and lungs, and are ready to move to the land as efts.
Once on land, they grow larger, their colors become duller, and they gradually reach sexual maturity, preparing to return to the water for the next breeding season.
The predators of newts vary with their life cycle stages. For instance, larvae typically face predation from various fish, including trout, minnows, sticklebacks, perch, and bass, among others. Aquatic insects such as water beetles and dragonfly nymphs prey on larvae in freshwater habitats. Additionally, some waterbirds, such as herons and ducks, may sometimes pick larvae from shallow waters.
Adult newts have predators in both aquatic and terrestrial habitats. When on land, they fall prey to small mammals, such as shrews, hedgehogs, foxes, and badgers. Additionally, birds, including crows, magpies, and other ground-feeding species, also feed on them. Snakes, especially grass snakes in Europe and garter snakes in North America, are also formidable predators of newts.
In water, adult newts are preyed upon by birds such as egrets and kingfishers, as well as large predatory fish like trout, pike, and bass.
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