User:Bcradd1/Alpine newt

Diet, predators and parasites
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.

Predators taking 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. Predator pressure can affect the phenotypic expression of developing larval alpine newts. Alpine newt larvae that experience predator presence tend to take longer to emerge from the larval stage, growing slower and emerging later in the season than newt larvae that do not experience predator pressure. They also exhibit 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. 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. When adult newts are in the presence of a predator, they tend to flee a majority of the time. However, this decision can depend on the newt’s sex and temperature, with male newts reacting differently at temperatures outside of the normal range. While both sexes tend to flee a majority of the time, this decision is not temperature sensitive in female newts but is in male newts, with female newts fleeing more reliably and at a greater speed at a greater range of temperatures than males who tend to flee at a slower speed and remain immobile while secreting tetrodotoxin when the temperature is outside of the norm.

Parasites include parasitic worms, leeches, the ciliate Balantidium elongatum, and potentially toadflies. A ranavirus transmitted to alpine newts from midwife toads in Spain caused bleeding and necrosis. 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.