Hedgehogs a deadly pest

The lovable hedgehog portrayed by Beatrix Potter as Mrs Tiggywinkle has been revealed by researchers to have a darker side.

New Zealand has one of the world's biggest hedgehog populations but Landcare Research scientists say they should really be ranked among noxious pests - such as stoats, ferrets, and possums - munching their way through native wildlife.

"Hedgehogs are responsible for significant levels of predation on skinks and ground-nesting native birds' eggs," Landcare Research scientist Chris Jones said.

Hedgehogs posed a consistent background threat and mature females might actually be the worst culprits in preying on rare native invertebrates.

While all hedgehogs posed a threat, mature females fed on quick and easy sources of high energy, such as eggs and lizards, during their own breeding season.

Dr Jones said he recommended landowners lay traps for hedgehogs at the time of year ground-nesting birds began to breed, and in the autumn, when female hedgehogs could be specifically targeted.

"Males go into hibernation much earlier than females, who must race to build up food reserves after a taxing breeding season and before hibernation," he said.

Hedgehogs - introduced in the late 19th century - had now multiplied to number between two and four per hectare in most areas, reaching as many as eight per hectare in optimum conditions.

"Hedgehogs are regarded with benign indifference by most New Zealanders, who tend to see them as appealing creatures that eat garden and pasture pests," he said.

The hedgehog's diet consisted mainly of invertebrate insects, but there was plenty of evidence from their native Europe that they ate eggs and chicks of ground-nesting birds.

In New Zealand, video monitoring by the Department of Conservation over five years has shown that hedgehogs are responsible for about 20 per cent of all recorded predation of banded dotterel and black-fronted tern nests in a braided riverbed system in the Mackenzie Basin.

An analysis of gut contents from 615 hedgehogs trapped in the Mackenzie basin showed native lizard remains (mainly skinks) were present in three times as many adult female guts as adult males.

"This level of predation is obviously a threat to skinks, some of which are rare, and most of which already face decreasing habitat and predation from other introduced pests such as stoats and feral cats," Dr Jones said.

And because hedgehogs were natural insect-eaters, they should also be considered as a threat to native beetles and other insects.

"In the Mackenzie basin, hedgehog guts were found to contain rare endemic native beetles and weta, with one gut containing 283 weta legs," he said.

- NZPA