Introduction and Scope
Mammals are a highly successful group of animals in that they have conquered even the most hostile environments and developed impressive specializations in the process. Some, like the shrews Suncus or Crocidura, weigh only a few grams and are thus smaller than the largest insects. The whales, on the other hand, are millions of times more massive, the blue whale, Balaenoptera musculus, reaching a weight of 100 metric tons and more. Some species, like the Bathyergidae, stay below the ground throughout their life, while others live in the desert, or climb in the mountains, wade through swamps, or even venture out into the open sea without ever returning to the shore. Petaurus, Cynocephalus, as well as a variety of others are gliders and the Chiroptera are all highly skilled flyers, while others, like the antarctic Weddell seal, Leptonychotes, spend most of their time near or under the ice, diving for food. The bats use a sophisticated echo-location system, based on the emission an reception of ultrasonic sounds, as do the dolphins. Mysticetes are capable of communicating over large distances using very low frequences. Last but not least, man owes much of his superiority to the development of language.