Newt
During the subsequent few months, the larvae undergo metamorphosis, during which they develop legs, and the gills are absorbed and replaced by air-breathing lungs. Some species, such as the North American newts, also become more brightly coloured during this phase. Once fully metamorphosised, they leave the water and live a terrestrial life, when they are known as "efts". Only when the eft reaches adulthood will the North American species return to live in water, rarely venturing back onto the land. Conversely, most European species live their adult lives on land and only visit water to breed.
Italian crested newt
Newts of many different species are often found congregating in ponds, therefore niche overlap is very common. "T. carnifex" has adapted a specialized niche, to avoid species competition. Fasola (1993) discovered that during reproduction, water depth is the most important factor, and to avoid competition "T. carnifex" reproduces in deeper waters. Compared to most adult newts, "T. carnifex" is significantly more nocturnal and this helps to reduce resource competition between other newts who are more active during the day. During metamorphosis, "T. carnifex" becomes roughly eleven times heavier than other smaller newt species in a specific pond. The weight of "T. carnifex" allows it to prey on other species of newts, and therefore allows for an increase in its survival rate. Buskirk (2007) found that when "T. carnifex" was exposed to smaller species of newts, such as "T. helveticus", they caused delayed metamorphosis and decreased fitness in "T. helveticus". Conversely, when exposed to a newt species that had a larger body mass, "T. carnifex" did not affect metamorphosis or fitness in the opposite newt. Buskirk proposed that body size of Triturus newts plays a large role in the determination of species interactions in a natural wetland environment. Due to the larger body size of "T. carnifex", positive interactions with other smaller newt species is limited and allows for more resources and environment for "T. carnifex".