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
Wu "et al". (2007) found that when larvae are placed in a homogeneous temperature environment, they do not need to use behavioral thermoregulation and instead only use metabolic compensation. However, when placed in an environment with a variation of temperatures, newts will use both behavioral thermoregulation and metabolic compensation. Samajov and Gvozdik (2009) discovered that when adult newts dive at higher temperatures, they reduce the amount of time in their dive in order to reduce the cost on thermoregulation. Samajov and Gvozdik did not take into consideration that newts respire aerially, as well as cutaneously, and so the frequency and the duration of the dives recorded could have been affected by the amount of dissolved oxygen in the water. Adult newts alter the speed in which they dive between descents and ascents. Descents affect thermoregulation by using more energy, and so newts will often choose a passive descent, rather than swimming down to forage for food. When "T. carnifex" ascends, thermoregulation is not as affected because newts have been known to increase their buoyancy by expelling excess gasses. By altering the behavior used as a larvae and when swimming, "T. carnifex" can effectively thermoregulate.