Småpattedyrfaunaen på Anholt og Sprogø
Year: 2024
Type: article
Abstract: The small mammals of the Islands of Anholt and Sprogø After the latest Ice Age’s glacial maximum Denmark was a contin- uous landmass, landlocked with both England, Sweden, Germa- ny, and Poland until approximately 8.500 years ago. The island of Sprogø was formed as part of a marginal moraine from the Young Baltic glacier advance. The isolation occurred when land sub- sidence and water level rises caused rivers from the Baltic Sea to break through the land area between Lolland-Falster and Rügen, and the Great Belt was formed. During the subsequent extensive sea level rise, many other Danish islands were formed, including Anholt. When these events occurred, Denmark was covered by a mixed deciduous forest with e.g., hazel, birch, and pine, and many of the animal species we know today, were present including small mammal species such as rodents, shrews, and small preda- tors. The now isolated islands therefore probably predominantly supported populations of small mammals which typified forest. It should, however, be mentioned, that Sprogø since 1998 has been connected to Funen and Zealand by the Great Belt Bridges and the Eastern railway tunnel. Anholt is one of the most isolated among smaller Danish is- lands and until recently only one small mammal species, the house mouse (Mus musculus), was present probably represent- ing an introduction in historical times. In 2022, several dead, yellow-necked mice (Apodemus flavicollis) were found in houses, and subsequent livetraping in the fall confirmed its presence. In October 2022, small mammals were livetraped on the island of Sprogø. Ninety-six trap nights resulted in 85 captured small mammals, comprising 70 bank voles (Clethrionomys glareolus), 12 wood mice (Apodemus sylvaticus), and 3 yellow-necked mice. Bank voles and wood mice were present in all habitats on the island, but bank voles were more numerous. Presumably all three species were present in Denmark before Sprogø became an island. Based on this history, we consider it most likely that our catches of species typifying forest show that the small mammal fauna has been preserved intact from the time when Sprogø was part of a forest-covered mainland. However, we cannot rule out that later introductions have occurred. On the other hand, the small mammals on Anholt must have been intro- duced by humans. The house mouse on Anholt and the bank vole on Sprogø are examples of small mammal species that, in the absence of com- petition, can occupy habitats in which they would not occur in areas with richer small mammal faunas and mammal predators.
Authors: Christensen, Jens Tang; id_orcid 0000-0003-2370-2702, Jensen, Thomas Secher
Institutions: Aarhus University, Natural History Museum of Denmark
Language: Danish
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W4412219151