Why do islands give rise to such unusual creatures?

1. Land of opportunity

Islands make up a sixth of all land on Earth. Some are formed from lava expelled by volcanoes under the sea, such as the Hawaiian Islands. Others, like Madagascar, are created when landmasses break apart over hundreds of millions of years.

Isolated from the mainland, a new island often provides a unique habitat. With its own set of conditions, life can evolve differently. Some creatures develop the most unusual traits to survive – and thrive – in their new home. In many cases, separated from their mainland ancestors, they eventually transform into new species altogether.

2. CLICKABLE: Making the journey

The water that surrounds islands makes them difficult to reach. Click on the labels to find out how animals and plants discover remote areas.

3. Evolution runs riot

When an animal or plant arrives at an island for the first time, the new environment will usually be different from the one it’s used to. As a result, a species will gradually adapt to survive or die out.

Over time, its appearance, behaviour and the way its body works might change – to become more successful at evading a predator, or more efficient at exploiting a new food source. For example, it might develop longer limbs, or lose those it no longer needs. Eventually, it may alter so much that it can no longer breed with its original species: it’s evolved into an entirely new species.

An island, especially a remote one, may be colonised by relatively few species. This allows the members of one species to exploit numerous different lifestyles, or ‘niches’ – a phenomenon called adaptive radiation. As the individual groups adapt to their different niches, they may evolve into distinct species. This is how one ancestor can eventually lead to the evolution of many new species – often looking and behaving quite different from each other.

Professor Richard Fortey explores how more than 50 species of Hawaiian Honeycreeper evolved from a single ancestor. (Nature's Wonderlands: Islands of Evolution, BBC Four, 2016).

4. CLICKABLE: Unusual adaptations

Click on the labels to discover how these island creatures evolved such extraordinary traits.

Learn more about this topic:

How did complex life begin?
Life Lessons
Ecosystems and Biomes