The alpine newt (Ichthyosaura alpestris ) is a species of newt native to continental Europe and introduced to Great Britain and New Zealand. Adults measure 7–12 cm (2.8–4.7 in) and are usually dark grey to blue on the back and sides, with an orange belly and throat. Males are more conspicuously coloured than the drab females, especially during breeding season.
The alpine newt occurs at high altitude as well as in the lowlands. Living mainly in forested land habitats for most of the year, the adults migrate to puddles, ponds, lakes or similar water bodies for breeding. Males court females with a ritualised display and deposit a spermatophore. After fertilisation, females usually fold their eggs into leaves of water plants. The aquatic larvae grow up to 5 cm (2.0 in) in around three months before metamorphosing into terrestrial juvenile efts, which mature into adults at around three years. In the southern range, the newts sometimes do not metamorphose but keep their gills and stay aquatic as paedomorphic adults. Larvae and adults feed mainly on diverse invertebrates and themselves fall prey to dragonfly larvae, large beetles, fish, snakes, birds or mammals.
Populations of the alpine newt started to diverge around 20 million years ago. At least four subspecies are distinguished, and some argue there are several distinct, cryptic species. Although still relatively common and classified as Least Concern on the IUCN Red List, alpine newt populations are decreasing and have locally gone extinct. The main threats are habitat destruction, pollution and the introduction of fish such as trout into breeding sites. Where it has been introduced, the alpine newt can potentially transmit diseases to native amphibians, and it is being eradicated in New Zealand.
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starts withThe alpine newt is medium-sized and stocky. It reaches 7–12 cm (2.8–4.7 in) length in total, females measuring roughly 1–2 cm (0.39–0.79 in) longer than males, and a body weight of 1.4–6.4 g. The tail is compressed sideways and is half as long or slightly shorter than the rest of the body. During their life in water, both sexes develop a tail fin, and males a low (up to 2.5 mm), smooth-edged crest on their back. The cloaca of males swells during breeding season. The skin is smooth during the breeding season and granular outside it, and is velvety during the animal's land phase.: 213 : 10–13
The characteristic dark grey to bright blue of the back and sides is strongest during breeding season. This base colour may vary to greenish and is more drab and mottled in females. The belly and throat are orange and only occasionally have dark spots. Males have a white band with black spots and a light blue flash running along the flanks from the cheeks to the tail. During breeding season, their crest is white with regular dark spots. Juvenile efts, just after metamorphosis, resemble adult terrestrial females, but sometimes have a red or yellow line on the back. Very rarely, leucistic individuals have been observed.: 213 : 12–36
While these traits apply to the widespread nominate subspecies, I. a. alpestris, the other subspecies differ slightly. I. a. apuana often has dark spots on the throat and sometimes on the belly. I. a. cyreni has a slightly rounder and larger skull than the nominate subspecies but is otherwise very similar. In I. a. veluchiensis, females have a more greenish colour, spots on the belly, sparse dark spots on the lower tail edge, and a narrower snout, but these differences between subspecies are not consistent.: 214–215 : 33–36
Larvae are 7–11 mm long after hatching and grow to 3–5 cm (1.2–2.0 in) just before metamorphosis. They initially have only two small filaments (balancers), between the eyes and gills on each side of the head, which later disappear as the forelegs and then the hindlegs develop.: 215 : 97–104 The larvae are light brown to yellow and initially have dark longitudinal stripes, which later dissolve into a dark pigmentation that is stronger towards the tail. The tail is pointed and sometimes ends in a short filament. Alpine newt larvae are more robust and have wider heads than those of the smooth newt and palmate newt.: 215 : 13–14
The alpine newt is native to continental Europe. It is relatively common over a large, more or less continuous range from northwestern France to the Carpathians in Romania, and from southern Denmark in the north to the Alps and France just north of the Mediterranean in the south, but absent from the Pannonian basin. Isolated areas of distribution in Spain, Italy and Greece correspond to distinct subspecies (see section Taxonomy: Subspecies above).: 214–215 : 39–46 Alpine newts have been deliberately introduced to parts of continental Europe, including within the boundaries of cities such as Bremen and Berlin.: 39–46 Other introductions have occurred to Great Britain, mainly England but also Scotland, and Coromandel Peninsula in New Zealand.
The alpine newt can occur at high elevation and has been found up to 2,370 m (7,780 ft) above sea level in the Alps. It also occurs in the lowlands down to sea level. Towards the south of its range, most populations are found above 1,000 m (3,300 ft).: 51–59
Forests, including both deciduous and coniferous forests (pure spruce plantations are avoided), are the main land habitat. Less common are forest edges, brownfield land, or gardens. Populations can be found above tree line in the high mountains, where they prefer south-exposed slopes. The newts use logs, stones, leaf litter, burrows, construction waste or similar structures as hiding places.: 216 : 54–59
Aquatic breeding sites close to adequate land habitat are critical. While small, cool water bodies in forested areas are preferred, alpine newts tolerate a wide range of permanent or non-permanent, natural or human-made water bodies. These can range from shallow puddles over small ponds to larger, fish-free lakes or reservoirs and quiet parts of streams. Damming by beavers creates suitable breeding sites. Overall, the alpine newt is tolerant regarding chemical parameters such as pH, water hardness and eutrophication. Other European newts such as the crested, smooth, palmate or Carpathian newt often use the same breeding sites, but are less common at higher elevation.: 216 : 47–54
Alpine newts are usually semiaquatic, spending most of the year (9–10 months) on land and only returning to the water for breeding. The efts are probably terrestrial until they reach sexual maturity.: 54 At lower altitudes this occurs in males after around three years, and in females after four to five years. Lowland alpine newts can reach the age of ten. At higher altitudes, maturity is reached only after 9–11 years, and the newts can live for up to 30 years.: 215
Alpine newts are diet generalists, taking mainly different invertebrates as prey. Larvae and adults living in the water eat for example plankton, larvae of insects such as chironomids, crustaceans such as ostracods or amphipods, and terrestrial insects falling on the surface. Amphibian eggs and larvae, including of their own species, are also eaten. Prey on land includes insects, worms, spiders and woodlice.: 68–72
Predators of adult alpine newts are snakes such as the grass snake, fish such as trout, birds such as herons or ducks, and mammals such as hedgehogs, martens or shrews. Under water, large diving beetles (Dytiscus ) can prey on newts, while small efts on land may be predated by ground beetles (Carabus ). For eggs and larvae, diving beetles, fish, dragonfly larvae, and other newts are the main enemies.: 73–77 Predator pressure can affect the phenotype of developing alpine newts. In an experiment, alpine newt larvae raised in the presence of caged dragonfly larvae took longer to emerge from the larval stage, growing slower and emerging later in the season than newt larvae that did not experience predator presence. They also exhibited traits such as darker coloration, larger body size, a proportionally larger head and tail, and more wary behavior than their predator-free counterparts.
Threatened adult newts often take on a defensive position, where they expose the warning colour of their belly by bending backwards or raising their tail and secrete a milky substance.: 74–75 Only trace amounts of the poison tetrodotoxin, abundant in the North American Pacific newts (Taricha ), have been found in the alpine newt. They also sometimes produce sounds, whose function is unknown.: 74–75 When adult newts are in the presence of a predator, they tend to flee a majority of the time. However, the decision of whether or not to flee can depend on the newt’s sex and temperature. In an experiment, female newts fled more often and at a greater speed over a greater range of temperatures than males, who tended to flee at a slower speed and remained immobile while secreting tetrodotoxin when the temperature was outside of the normal range.
Parasites include parasitic worms, leeches, the ciliate Balantidium elongatum, and potentially toadflies.: 77 A ranavirus transmitted to alpine newts from midwife toads in Spain caused bleeding and necrosis.: 142 The chytridiomycosis-causing fungus Batrachochytrium dendrobatidis has been found in wild populations, and the emerging B. salamandrivorans was lethal for alpine newts in laboratory experiments.
