Like other newts,
Triturus species develop in the water as larvae, and return to it each year for breeding. Adults spend one-half to three-quarters of the year on land, depending on the species, and thus depend on both suitable aquatic breeding sites and terrestrial habitats. After larval development in the first year, juveniles pass another year or two before reaching maturity; in the north and at higher elevations, this can take longer. The larval and juvenile stages are the riskiest for the newts, while survival is higher in adults. Once the risky stages passed, adult newts usually attain an age of seven to nine years, although individuals of the northern crested newts have reached 17 years in the wild.
Aquatic phase pond). The aquatic habitats preferred by the newts are stagnant, mid- to large-sized, unshaded water bodies with abundant
underwater vegetation but without fish, which prey on larvae. Typical examples are larger
ponds, which need not be of natural origin; indeed, most ponds inhabited by the northern crested newt in the UK are human-made. Examples of other suitable secondary habitats are ditches, channels, gravel pit lakes, garden ponds, or (in the Italian crested newt) rice paddies. The Danube crested newt is more adapted to flowing water and often breeds in river margins,
oxbow lakes or flooded
marshland, where it frequently co-occurs with fish. Other newts that can be found in
syntopy with
Triturus species include the
smooth, the
palmate, the
Carpathian, and the
alpine newt. Adult newts begin moving to their breeding sites in spring when temperatures stay above . This usually occurs in March for most species, but can be much earlier in the southern parts of the distribution range. Southern marbled newts mainly breed from January to early March and may already enter ponds in autumn. The time adults spend in water differs among species and correlates with body shape: while it is only about three months in the marbled newts, it is six months in the Danube crested newt, whose slender body is best adapted to swimming.
Triturus newts in their aquatic phase are mostly nocturnal and, compared to the smaller newts of
Lissotriton and
Ichthyosaura, usually prefer the deeper parts of a water body, where they hide under vegetation. As with other newts, they occasionally have to move to the surface to breathe air. The aquatic phase serves not only for reproduction, but also offers the animals more abundant prey, and immature crested newts frequently return to the water in spring even if they do not breed.
Terrestrial phase female rolled up, exposing its bright orange underside to deter a predator During their terrestrial phase, crested and marbled newts depend on a landscape that offers cover, invertebrate prey and humidity. The precise requirements of most species are still poorly known, as the newts are much more difficult to detect and observe on land. Deciduous woodlands or
groves are in general preferred, but conifer woods are also accepted, especially in the far northern and southern ranges. The southern marbled newt is typically found in Mediterranean oak forests. In the absence of forests, other cover-rich habitats, as for example
hedgerows,
scrub, swampy meadows, or
quarries, can be inhabited. Within such habitats, the newts use hiding places such as logs, bark, planks, stone walls, or small mammal burrows; several individuals may occupy such refuges at the same time. Since the newts in general stay very close to their aquatic breeding sites, the quality of the surrounding terrestrial habitat largely determines whether an otherwise suitable water body will be colonised. Juveniles often
disperse to new breeding sites, while the adults in general move back to the same breeding sites each year. The newts do not migrate very far: they may cover around in one night and rarely disperse much farther than . For orientation, the newts likely use a combination of cues including odour and the calls of other amphibians, and
orientation by the night sky has been demonstrated in the marbled newt. Activity is highest on wet nights; the newts usually stay hidden during daytime. There is often an increase in activity in late summer and autumn, when the newts likely move closer to their breeding sites. Over most of their range, they
hibernate in winter, using mainly subterranean hiding places, where many individuals will often congregate. In their southern range, they may instead sometimes
aestivate during the dry months of summer.
Diet and predators Like other newts,
Triturus species are carnivorous and feed mainly on invertebrates. During the land phase, prey include
earthworms and other
annelids, different
insects,
woodlice, and
snails and slugs. During the breeding season, they prey on various aquatic invertebrates, and also
tadpoles of other amphibians such as the
common frog or
common toad, and smaller newts. Larvae, depending on their size, eat small invertebrates and tadpoles, and also smaller larvae of their own species. The larvae are themselves eaten by various animals such as carnivorous invertebrates and
water birds, and are especially vulnerable to predatory fish. Adults generally avoid predators through their hidden lifestyle but are sometimes eaten by
herons and other birds, snakes such as the
grass snake, and mammals such as
shrews,
badgers and
hedgehogs. They secrete the poison
tetrodotoxin from their skin, albeit much less than for example the North American
Pacific newts (
Taricha). The bright yellow or orange underside of crested newts is a
warning coloration which can be presented in case of perceived danger. In such a posture, the newts typically roll up and secrete a milky substance. ==Reproduction==