What is Island Gigantism?

There’s an amazing phenomenon in the animal kingdom where certain species of animals that live on islands, become much larger than the same animal that lives on the mainland. This is called Island Gigantism.


The size of the island itself often plays apart in the size of the animal and the rapidness that it evolves. Often the smaller the island, the bigger the animal is likely to get!

This phenomenon has been observed in many varieties of species from lizards, to rats, to bugs!

  • Galapagos Tortoise (The largest tortoise in the world)
  • Komodo Dragons (The largest lizard in the world)
  • Giant Weta (this giant insect can get up to 4 inches long!)
  • Flores Giant Rat (this rat is twice the size of a normal rat!)

There are many different theories as to why animals that live on islands get so big

  • A Lack of Predators: Being small allows prey animals to hide easily, but many islands lack land dwelling predators. This would allow prey animals to grow much larger without being eaten.


  • The Need for Less Resources: With some animals, such as the tortoise, larger ones can go a much longer time without food or water. This can be useful on an island where resources like food and water, might be harder to find.


  • Territorial Benefits: Many larger reptiles on islands are territorial species, suggesting that being larger on islands gave them an advantage in competing for territory.

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