The Bailiwick is not blessed with an array of mammals. Larger ones such as deer, foxes and badgers are absent. Red squirrels are present in Jersey (introduced) but there are none here, neither is there sufficient suitable habitat to sustain a population.
Rabbits were introduced, probably by the Normans who kept enclosed warrens (areas named La Garenne) for a ready source of meat and fur. Despite myxamitosis and other more recent viruses, the rabbit population is widespread across Guernsey, mainly on the cliffs and at L’Ancresse.
Black Rats have been wiped out in Guernsey by the invasive and, in their terms, very successful, introduced Brown Rat. The native species is still present in small numbers in Sark. Brown Rats have been devastating for many local species, particularly ground nesting or shore nesting birds such as Meadow Pipit and Oystercatcher.
Hedgehogs are an introduced species, including Alderney’s blond hedgehogs. Doubtless they have had a negative effect on ground-nesting birds – they will take eggs and chicks. Overall, they have not been invasive and have become a welcome part of our island’s wildlife. Numbers in the UK have seriously declined over the past decade and many local people appreciate seeing these nocturnal visitors in their gardens.
The Guernsey Vole or Mulot, is unique to the island.
House Mouse, Wood Mouse and Great White-toothed Shrew are also present.
Natural history of the Bailiwick of Guernsey 