destroyed the underlying tundra from which the plant life cannot recover during the non-skiing months, whereas areas that still practice a natural piste type of ski slope building preserve the fragile underlayers. Fauna The Alps are a habitat for 30,000 species of wildlife, ranging from the tiniest snow fleas to brown bears, many of which have made adaptations to the harsh cold conditions and high altitudes to the point that some only survive in specific micro-climates either directly above or below the snow line. The largest mammal to live in the highest altitudes are the alpine ibex, which have been sighted as high as . The ibex live in caves and descend to eat the succulent alpine grasses. Classified as antelopes, chamois are smaller than ibex and found throughout the Alps, living above the tree line and are common in the entire alpine range. Areas of the eastern Alps are still home to brown bears. In Switzerland the canton of Bern was named for the bears but the last bear is recorded as having been killed in 1792 above Kleine Scheidegg by three hunters from Grindelwald. Many rodents such as voles live underground. Marmots live almost exclusively above the tree line as high as . They hibernate in large groups to provide warmth, and can be found in all areas of the Alps, in large colonies they build beneath the alpine pastures. Golden eagles and bearded vultures are the largest birds to be found in the Alps; they nest high on rocky ledges and can be found at altitudes of . The most common bird is the alpine chough which can be found scavenging at climber's huts or the Jungfraujoch, a high-altitude tourist destination. Reptiles such as adders and vipers live up to the snow line; because they cannot bear the cold temperatures they hibernate underground and soak up the warmth on rocky ledges. The high-altitude Alpine salamanders have adapted to living above the snow line by giving birth to fully developed young rather than laying eggs. Brown trout can be found in the streams up to the snow line. Molluscs such as the wood snail live up the snow line. Popularly gathered as food, the snails are now protected. Several species of moths live in the Alps, some of which are believed to have evolved in the same habitat up to 120 million years ago, long before the Alps