Image description

Natural History of Scilly

Collage of wildlife photographs

Wildlife overview

  • What makes Scilly special
  • The history behind Scilly's wildlife
  • Explorers and colonisers
  • Endemic, Scillonian wildlife
  • Alien invaders?
  • Resources and Citizen Science Links

Wildlife notes

  • Species unique to Scilly
  • Nationally rare species
  • Southern species
  • Migratory species
  • Unexpected life cycles

      Visit Wildlife notes page >>

Wildlife timeline

  • Arrivals and Introductions

Wildlife overview


What makes Scilly special for wildlife?

Scilly has a unique assembly of native, migrant and introduced species. The sea surrounding Scilly isolates it from mainland Britain and the warm North Atlantic Drift current keeps the islands frost-free. In three areas around Scilly - the Irish Sea Front, the Ushant Front and the Continental Shelf - cold nutrient-rich waters mix with the warmer water of the North Atlantic Drift current. The combination of warmth and nutrients encourages the growth of phytoplankton (microscopic plants) which are a rich food source for planktonic animals and turns these three areas into feeding grounds for fish, sea birds and sea mammals living in and around Scilly. However, the tidal currents that circle round Scilly isolate it from these feeding grounds and Scilly lacks any rivers or estuaries to fertilize the coastal water. These geographical features account for the clear blue of the sea and limit the numbers of seashore species; they also hamper attempts to farm mussels and oysters here.

The history behind Scilly’s wildlife


In the last Ice Age, 20,000 years ago, the Atlantic coast was 100 km west of Scilly. At that time, Scilly, Ireland, Britain, mainland Europe and Scandanavia were all joined. An ice sheet covered most of Britain, just reaching the north ends of Tresco and St Martins. The plants and animals that lived where the Scillies are now were characteristic tundra wildlife (BBC Pleistocene wildlife video) and some of these, lichens, Dwarf Pansy, Greater Tussock Sedge and Red barbed ant remain in the islands. 

After the last Ice Age, changes in climate and sea level isolated Scilly, first from continental Europe and then from mainland Britain, restricting the numbers of land animals and allowing some species to evolve separately and differently, giving rise to unique species special to Scilly (endemic species). 

Since Neolithic times, human activity has linked Scilly with the rest of the world, importing alien species, both accidentally and intentionally, creating the extraordinary array of plants and animals that thrive in the comparative warmth offered by the North Atlantic Drift current.


These features of Scilly’s geography and history have shaped Scilly’s flora and fauna so that the wildlife we see here today covers a complete range from the exclusive, ‘endemic’ species, like the Scilly shrew, through nationally rare species such as the giant gobi, Lesne’s earwig, many lichens, red seaweeds and mosses, to common species such as shore crab and bracken. Scilly also houses what are arguably out-of-place alien imports such as stick insects and the pittosporum trees that are used as windbreaks.

Read more about unsual species >>

Read more - Timeline of arrivals and introductions >>


Explorers and colonizers

The seashore presents many challenges to its wildlife. How do the seashore animals arrive and stay on the part of Scilly’s rocky and sandy coastline that suits them best? 

Seashore animals use a variety of breeding strategies to ensure the young remain in the preferred habitat and colonise new habitats as they become available: seahorses, rock periwinkles, and sandhoppers hold their eggs in brood pouches until they hatch; lugworm females lay their eggs in their burrows, where they hatch and develop a little before being washed to nearby sites; plaice, limpets and sea urchins broadcast eggs and sperm and their fertilized eggs are the start of a planktonic phase of their life cycle. Most marine invertebrates have planktonic larvae which are microscopic and are poor swimmers but hitch rides on different currents by moving up or down, arriving back in Scilly when they are ready to settle in their new habitat on the shore.

Seashore breeding strategies

Planktonic larvae

Endemic Scillonian wildlife


Scilly has been isolated from mainland Europe for 17,000 years and from mainland Britain for about 7,000 years. In this time some species have changed genetically making them ‘endemic’ (unique) to the islands. Some changes visibly alter their shape, colour or behaviour, others are only detectable biochemically as changes in DNA and proteins. The Scilly Shrew, St Martins Ant, Scillonian Specked Wood Butterfly, Scilly Bee, Shore Dock, Sea Rush and St Martins Buttercup are all different to varying extents from their mainland or European counterparts and are unique to Scilly. Studying these differences in local populations can help guide conservation strategies. 

Read more about the St Martins and and the Lesser White-toothed Shrew:

St Martins Ant DNA forensics

   Scilly Shrew A puzzle with a piece missing...

Alien invaders?


Many plants you may associate with Scilly are not native to the islands but were brought here from South Africa (hottentot fig), from New Zealand (pittosporum), or from California (Monterey pine). These plants have naturalized in Scilly and provide food and shelter for native wildlife. However, alien species can be a threat, by competing with native species or by interbreeding with species that are unique to Scilly. As well as resident and migrant wildlife, many vagrant species of birds, turtles and some insects pass through Scilly, finding food and shelter here. Occasionally, such vagrancy leads to colonisation, as has happened in the past, for example with the Eastern Collared Dove in the 1960s, and may be happening now with the Little Egret.

Timeline of arrivals and introductions >>

On Line Resources

Isles of Scilly Pages

Isles of Scilly Wildlife Isles of Scilly Biodiversity Audit 2008

Botanical Cornwall Group - Scilly - Webpages include a Rare Plant Register

Isles of Scilly Seabird Recovery Project

Identification guides

Seaweed identification field guide

British lichens picture index

Butterflies and moths Identification and Conservation

Natural History Museum Online Identification Forum to help you identify your find

British Flora Online Atlas of the British and Irish Flora

Marine Life MarLIN The Marine Life Information Network 

ARKive webpages of animal and plant species, including the most endangered  

Citizen Science

Online wildlife recording for Cornwall and Scilly- welcomes submissions from pros and amateurs

Isles of Scilly Seabird Recovery Project

BugLife including the Oil Beetle Hunt

Natural History Museum projects

Zooniverse projects online, including Plankton Portal, Penguin Watch and Whales as Individuals 

The main oceanographic features affecting Scilly's wildlife (adapted from Mason et al 2006  Read more >>)

In the last Ice Age, Scilly was 100 km inland, experiencing arctic conditions - much of its wildlife survived in refugia around the Mediterranean.

Read more >> 

Planktonic larvae

Flower and distinctive seedpods of endemic buttercup.

St Martins Buttercup

Little Egret