Insular dwarfism

Inselverzwergung is a biological phenomenon in which body size of animal species that live on an island without predators or human intervention, significantly decreases over generations of time.

Examples of Inselverzwergung include:

  • Malagasy hippos and hippos on Mediterranean islands.
  • Various, partly extinct dwarf elephant species, including the Bornean elephant dwarf, dwarf forms of elephant and mammoth on some Mediterranean islands such as the Sicilian dwarf elephant.
  • The extinct Honshu Wolf in Japan.
  • Homo floresiensis, a discovered on the island of Flores members of the genus Homo.
  • The dwarf mammoth, was located in the Channel Islands of California, and in another variety on Wrangel Island.
  • The island gray fox on the California Channel Islands. He has evolved from the gray fox after specimens of this species arrived on the northern three Channel Islands. Today this kind of genuine fox is with a body size that corresponds approximately to a domestic cat, much smaller than the parent form.
  • Svalbard reindeer on the island of Spitsbergen are only 65 cm high, while reindeer on the mainland have an average shoulder height of about 110 cm.

Fossil was the phenomenon also in the described sauropod dinosaur Europasaurus 2006 demonstrated that an island in what is now northern Germany lived during the late Jurassic. While were closely related forms on the mainland reach up to 40 meters in length and a weight of 50 to 80 tons, Europasaurus was already at about 6.20 meters in length and a ton of mature weight.

The tendency to Inselverzwergung is also evident in raccoons, rabbits, pigs and deer. Snakes also tend, with few exceptions for Inselverzwergung. Small rodents on islands on the other hand tend to Inselgigantismus, ie island forms of animal ordering tend to develop significantly larger body shapes as on the mainland. The tendency to gigantism can also be observed in iguanas, geckos, skinks, lizards and dragons Canaries such as the Komodo dragon.

Initial research to Inselverzwergung come from the Canadian biologist J. Bristol Foster ( b. 1932 ). For him, the adjustment mechanisms are in overpopulation of the decisive factor in whether a species to dwarfism or gigantism tends to.

On the Dodekanesinsel Tilos the bones of two different dwarf elephant species were recovered during excavations in the Charkadio Cave, which yielded the youngest 14C date of 1300 BC. In order for these dwarf elephants have become extinct only in the Bronze Age. Neolithic data derived from other Mediterranean islands.