Volunteers have been trying to save the hedgehogs

Government agency Scottish Natural Heritage (SNH) aims to kill 200 of the animals this year in an effort to save threatened wading birds, whose eggs the creatures eat.

On Monday night, five SNH "hedgehog hunters" used large spot lamps to try to track down the creatures.

Any hedgehogs found will be given a lethal injection.

Garden pests

However, animal welfare groups have launched two separate efforts to save as many of the animals as possible.

SNH confessed it would be "surprised" if it found any hedgehogs as the cold weather has caused them to hibernate for longer than expected.

Hedgehogs have been multiplying and spreading since a handful were introduced 30 years ago to keep down garden pests.

There are now about 5,000 in the Western Isles.

Scientific evidence has shown the animals eat the eggs of ground-nesting birds.

The cull has attracted media attention

Hedgehogs feeding on snipe, lapwing and redshank eggs have sent bird numbers on the island into freefall in recent years.

SNH spokesman George Anderson told BBC Scotland: "If we were not to take any action to stop this problem what would happen over a number of years is that the bird numbers would collapse.

"The hedgehogs would keep eating the eggs until the bird population had gone down to almost nothing."

He said studies had suggested that hedgehogs would compete for food if moved to a new area.

"Some of the animals you move in will starve and some of the animals already there will starve, so you have got an awful lot of upset and distress for the animals," he said.

Save hedgehogs

However, the research has been questioned by a consortium of animal welfare groups which includes Advocates for Animals and the St Tiggywinkles Wildlife Hospital.

They are now trying to save as many hedgehogs as possible from the cull.

Ross Minett, of Advocates for Animals, said the activists would not physically try to stop those involved.

"We are not here to break the law, we are here to save hedgehogs," he said.

"We are here to appeal to SNH not to cull them because they don't need culling."

The consortium is attempting to buy local knowledge by offering islanders �5 for each hedgehog they catch.