For the past ten years, Scottish Natural Heritage has been trying to tackle the prickly problem of the hedgehogs on North and South Uist in the Western Isles. And this spring the agency is going to have another go at proving the link between the arrival of the hedgehogs and the drastic decline in protected seabirds like dunlin, snipe, ringed plovers and lapwings.
The hedgehogs arrived in 1974, brought over from the mainland in a somewhat misguided attempt to control slugs and snails. The hedgehogs multiplied and have spread throughout the islands. And they have been eating the eggs of the rare wading birds. Since 1980, wader numbers have fallen from around 17,000 pairs to about half that today.
The Scottish government is under a European Union directive to protect this important sea bird population. But are the hedgehogs really to blame for the decline in waders or are other factors more important – like rats or other seabirds, or loss of habitat or food supplies or climate change? A team of two researchers is setting out this month to find out, using observation points, fixed cameras and temperature loggers buried in the sand. It’s part of a three year research project lasting till 2015 and costing £227,000.
Two years ago a similar study was begun but the results have proved inconclusive, partly because the fixed cameras leaked and partly because the sample sites were too few. The last full bird survey in the islands, in 2007, also proved inconclusive, finding no obvious trends. Numbers of redshanks and oystercatchers actually increased. Nor do we know exactly how many hedgehogs there are, estimates have varied from 3,500 to 7,000.
These unknowns are just the latest problems to beset this troublesome project. It began in 2003 with a decision by Scottish Natural Heritage (SNH) to cull hedgehogs in North and South Uist and in the island between them Benbecula. Fourteen trappers were employed, a million pounds was spent and hundreds of hedgehogs were killed. But there was a public outcry, led by the British Hedgehog Preservation Society and other animal welfare groups.
They set up the Uist Hedgehog Rescue service and offered to re-home the hedgehogs on the mainland. At first NHS maintained that that would be to condemn the animals to a slow lingering death since re-homing did not work. But it had to perform a swift u-turn when new research showed that over 60 per cent of hedgehogs survive relocation. 
Thus in 2007, SNH reached an agreement to pay Uist Hedgehog Rescue £60 per animal to have them relocated on the mainland. Since then 1600 hedgehogs have been taken to the Hissilhead Wildlife Centre in Ayrshire and prepared for their new homes in the surrounding countryside.
It was a turning point in SNH’s relations with the public. The agency learnt the lesson, rather painfully, that public opinion can often trump expert opinion. And since then, the experts have been much more careful about consulting widely before taking action.
The trapping of hedgehogs on the Uists still goes on, but on a much smaller scale. Only 135 animals were removed in 2011 and 193 last year. The number of trappers has fallen to just two but they are now assisted by a sniffer dog. Their job is to make sure hedgehogs don’t return to areas already cleared, particularly on North Uist.
But as the hedgehogs come out of hibernation and the nesting season begins, all eyes are on the scientists to see if they can establish once and for all just who or what is responsible for the decline of the Uist seabirds.