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
Oxygen consumption has normally been determined to be the most convenient and relevant measure of metabolic activity. With very few exceptions, oxygen consumption is reduced in response to starvation and physical inactivity, and increased in fed and active animals (Hawkins, 1995). Basal maintenance metabolism in ectotherms is relatively unchanged in response to variations in atmospheric temperatures, which would be advantageous to the newt’s survival in both their aquatic and terrestrial environments where temperatures can rapidly shift throughout the year.