Newt
Newts, as with salamanders in general and other amphibians, serve as bioindicators because of their thin, sensitive skin and evidence of their presence (or absence) can serve as an indicator of the health of the environment. Most species are highly sensitive to subtle changes in the pH level of the streams and lakes where they live. Because their skin is permeable to water, they absorb oxygen and other substances they need through their skin. Scientists study the stability of the amphibian population when studying the water quality of a particular body of water.
Iberian ribbed newt
"P. waltl" is more aquatic-dwelling than many other European tailed amphibians. Though they are quite able to walk on land, most rarely leave the water, living usually in ponds, cisterns, and ancient village wells that were common in Portugal and Spain in the past. They prefer cool, quiet, and deep waters, where they feed on insects, worms, and tadpoles.