Content on this page requires a newer version of Adobe Flash Player.

Get Adobe Flash player

 

Search in the Encyclopedia

Dieren en planten

Water en land

Mens en Milieu

Ecology   Island biology   
Roe deer on a tidal flat, The Inked Naturalist

Island biology

Life on an island is different than life on the mainland. That applies for plants and animals as well. There are often fewer predators or competitors. Remote islands that have been isolated for a long time can have animals that are found nowhere else in the world. Well known examples include giant tortoises on the Galapagos Islands. Sometimes, foreign species reach the island. The rabbit was a newcomer in Australia, didn't have any natural enemies and rapidly populated the continent. Indigenous marsupials ran into major problems. The fauna in Australia has been permanently altered since the rabbit arrived.

  • Island biology in the wadden region

    Up till 1000 years ago, the Wadden Islands were still connected to the peat grounds and marsh area that covered practically all of the northern Netherlands. As islands they are very young. In addition, they are no means remote, being situated relatively close to the mainland, so that many species of land animals have been able to reach the islands. Consequently, no endemic species have evolved here. However, there are unique variations, which deviate from their mainland relatives.

    On Texel, the water shrews are smaller than those on the mainland, and totally black instead of black and white. The wood mouse on Helgoland has a brick-red color, while elsewhere its back is yellow to light brown and its belly grayish white.

    Many animal species are lacking on the Wadden Islands. Moles, squirrels and foxes are not found on any of the Dutch Wadden Islands. They could easily live there however they have never reached the islands in the past and therefore have never colonized them. This has definite consequences for other animals. The lack of larger land predators is one of the reasons why gulls, ducks, curlews and short-eared owls have no problems nesting on the ground. The root vole is a species which is only found in swampy regions on the mainland. It loses the competition with the common vole on drier ground. However it is common throughout Texel, even in dry terrains, since there are practically no common voles on the island.

  • Presence of land mammals on the Dutch Wadden Islands
    SpeciesTXVLTSAMSCH
    hedgehog x x x x x
    common shrew     x    
    lesser shrew     x x  
    water shrew x        
    greater white-toothed shrew e       x
    hare x x x x x
    rabbit x x x x x
    bank vole e   e    
    field vole e     e  
    root vole x        
    common vole e     x  
    muskrat     e e  
    harvest mouse e   e e  
    wood mouse x x x x x
    common mouse x x x x x
    brown rat x     x x
    wild domestic cat x x x x x
    ferret-pole cat e     e  
    ermine x   x    
    roe deer     e x  
    x = native species, e= recently introduced


    On the Wadden Islands, animal species come and go. Most newcomers have been brought by people. They were purposely introduced on the island (rabbits, ermines, roe deer on Terschelling)  or got a lift accidentally (house mouse, brown rat, wild domestic cats). Sometimes it was made easy, when dams were built in the past (roe deer on Ameland).

    In 2009, someone brought a pregnant fox to Vlieland. It didn't take long before looting occurred in the bird colonies. In the winter of 2009/2010, nine foxes were caught. The tenth one supposedly is still living on the island.

    The greater white-toothed shrew has recently taken over Texel. One positive effect has been an increase in nesting barn owls, a consumer of this shrew. But the downside is that the special subspecies of water shrew, found only on Texel, can hardly be found anymore.