Most people don't realise that the Scottish wilderness is basically industrial wasteland: originally mostly forested, it's been clearfelled, then intensively farmed, then the farmers were ethnically cleansed and it was converted fairly crudely to grazing, and then when that was no longer viable it's largely been abandoned. Needless to say, all the predators (bear, wolves and lynx, mostly) are dead, while the useful food animals (red deer, roe deer) run wild.
The end result is devastation. It looks beautiful, but ecologically it's awful: there's a huge deer overpopulation, and they eat everything. Trees won't regenerate because saplings don't survive. Without trees the entire bottom of the ecosystem is missing, and without treeroots holding the tiny amount of soil together, it turns into mush.
If you spend a night out in the Scottish wilderness, even in the middle of summer it's _dead silent_. If there's water nearby you might hear a curlew. Occasional skylarks. You'll also probably hear the weird grunting of a herd of red deer across the glen. Contrast with Norway, where every flat surface is covered with dwarf birch and dwarf spruce, and there's birdsong everywhere...
(You do get Forestry Commission forests of Norwegian spruce. These are even worse; the trees are grown commercially, they're extremely fast growing, usually planted way too close together, they're clear cut every decade or so, and they're utterly barren. Not even the deer will go in.)
Every now and again you'll find a small area that's well fenced off enough to keep the deer out, and it'll be full of trees. But a massive, nationwide cull of deer is politically impossible (I know one estate owner who's received hate mail for culling the deer on his estate, as required by law). There are some attempts to reintroduce wolves, but people are understandably a bit leery. Lynx may be viable: apparently they're not big enough to pose much of a threat to the deer, but will at least keep them moving, which will help solve some of the overgrazing problem.
There's also a lot more awareness these days, with more fencing and planting, but it's all piecemeal, and it usually doesn't happen on the high moors and hillsides which are the most at risk.
So, um, yeah. Deer are a goddamned menace.