Restoring ecological balance to the British mammal fauna

1 The mammal fauna of the British Isles has seen major perturbations since the end of the last ice age, some natural and some anthropogenic. Today, 61 species of terrestrial mammals breed in the British Isles, but only 39 of them are native species, the rest have been introduced. Furthermore, 19 native species have disappeared from the fauna including all the large predators, lynx Lynx lynx, wolf Canis lupus and brown bear Ursus arctos.

2 Inevitably, these changes in species composition have been accompanied by major changes in community function including changes in patterns of energy flow through the mammalian community. For example, a high percentage of all the energy now flows through the introduced rabbit Oryctolagus cuniculus population and red deer Cervus elaphus, which, in the absence of natural predators, are living at extremely high densities.

3 Could the reintroduction of species help to reverse such changes in community structure and function? The successful return to the wild of species such as the Arabian oryx Oryx leucoryx and beaver Castor fiber has shown that reintroductions are certainly possible. However, the impact on community function of returned species is more difficult to evaluate.

4 This question is addressed in relation to the consequences for deer populations of any possible reintroduction of the wolf to Scotland. Based on what we know of wolves elsewhere, predictions are made about the likely demography and patterns of killing behaviour of introduced wolves. These values are then used to parameterize a Leslie matrix simulation of the impact of wolves on contemporary populations of red deer in Scotland. The simulations suggest very strongly that wolves are very unlikely to have any significant impact on the high-density populations of deer now living in the Scottish landscape.