Abstract:
The aim of this study was to review the role of European hedgehogs {Erinaceus europaeus) within a forest ecosystem and to assess their importance in ecosystem restoration. Telemetry and dietary studies were carried out on hedgehogs between December 1997 and March 1998 at Boundary Stream Mainland Island, Hawkes Bay
Male hedgehogs were found to have a mean home range of 29.4 hectares (range 9 — 47). These estimates are considerably larger than previously published New Zealand research, but matches that of overseas studies. Hedgehogs shared their home range with an average 5.4 other male hedgehogs, appeared not to defend territories and no evidence was found that the movements of one animal affected the movements of another. Habitat utilisation analysis concluded that while the hedgehogs visited all habitats present in the study area they foraged and spend the majority of their time within the forested habitats of the reserve.
Within Boundary Stream, the hedgehog diet was found to consist of 80% invertebrates and 20% other material (plant, bird, small mammal). Pill millipedes (Diplopoda), carabid beetles (Coleoptera) and spiders (Araneae) formed the majority of the invertebrate component of the hedgehog diet. There is evidence that the hedgehog is a selective predator rather than simply an opportunistic insectivore.
Boundary Stream Mainland Island is an attempt to develop full multiple-species management but this study shows that the current control procedures at Boundary Stream are not affecting the overall population of hedgehogs. Indications suggest an estimated population of 4400 hedgehogs within the reserve.
The hedgehog has three possible implications to the ecological restoration of Boundary Stream:
1. removal of large quantities of invertebrate biomass,
2. competition with other predators for food (e.g. robin, kiwi) and,
3. predation of vertebrate species.
The study suggests that the effort put into the reserve by the Department of Conservation to control other pest species is not achieving the full desired effect due to the population of hedgehogs present within the reserve. Therefore while the European hedgehog is not currently classified as a pest species, the evidence suggests that they must be considered when looking at full ecosystem restoration.
