Seuls quelques grands mammifères subsistent dans le monde : éléphants, hippopotames, rhinocéros et buffles, qui ont bien du mal à trouver leur place.
Rinoceronte, elefante, ippopotamo, bufalo e giraffa, sono chiamati "I grandi 5". I vantaggi ma anche le difficoltà che il loro peso e le loro dimensioni possono causare.
Over 10,000 years ago, many animals were considered "mega-fauna". This group consisted of herbivores that had taken a different path than horses or gazelles. Instead of evolving to a lighter, faster animal to escape predators, they decided to grow and to develop thick skins and huge, massive frames. Today, there are a still few animals that, in a way, are relics of this trend.