The red squirrel has long been in trouble in Britain in Ireland, where the colourful little rodent has suffered from competition by grey squirrels. The alien invader greys have not been physically attacking the reds, but they have been out-competing them, thanks partly to a more powerful digestive system. The greys also carry a disease that is barely noticeable to them but lethal to the reds. The march of the greys has seemed relentless, and it looked like the reds would end up pushed away into remote areas, where they would make up precarious and isolated communities.
Now, though it seems like the reds are on a bit of a comeback. In Britain there have been concerted programmes to trap and exterminate the greys, which have helped red squirrel numbers bounce back. But the reds have also gained from a tacit alliance with another endangered animal - the cute but fierce predator that is the pine marten. These little fellows have been protected in Ireland since the 1970s and in recent years their numbers and ranges have started to increase.
Although not averse to eating red squirrels, pine martens rarely do so as the agile reds are hard to catch. The chubby grey squirrels, on the other hand, make for easy prey for the pine martens, and analyse of their droppings reveals that the little predators are munching their way through the aliens. The hope is that spreading pine martens further through Britain and Ireland will help the red squirrels by controlling the greys without the bother of all those trapping and extermination programmes.