Roe deer abound in the woodlands of the south-east. The common seal frequents the shoals and sandbanks of Little Ferry and the Dornoch Firth. Both the grey seal and the common seal occur on the west and north coast.
The bird life of the county possesses great variety and interest. The osprey, kite, and merlin, are extinct, and the sea eagle now rarely breeds, though formerly fairly common on the west coast. The capercailzie, common in the seventeenth century, has long been extinct, and an attempt about 1870 to reintroduce it at Skibo was unsuccessful. The great northern, red-throated, and black-throated divers occur in the numerous lochans of the western parishes. In the boggy wilds of central Sutherland nest black-headed gulls. Many kinds of wild duck, the coot and the dunlin, while the plover and wild goose lay their eggs in the dry hummocks and knolls near such waters as Badanloch.
The marshes above the Mound provide cover to numerous water-fowl such as herons, oyster-catchers, and waders of every kind, who feed at low tide on the flats of Loch Fleet. Assynt contains about three hundred lochs, many of them alive in the season with such water-fowl as greenshanks, dunlin, and heron, while the call of the curlew is familiar on the moors, Ptarmigan, which have disappeared fro 111 the Griams and other eastern hills, are fairly numerous on Clibreck and the higher Assynt mountains.
Among summer visitors who come in numbers are the wheat-ear, whinchat, red start, white throat, willow wren, wood wren, sedge warbler, grey wagtail, ringed plover, fly-catcher, night jar, arctic tern, and lesser tern. The redwing, fieldfare, shrike, and snow bunting are autumn visitors. The latter has been known to nest in some high corries of the western mountains. Among rarer resident birds of the county are the raven, magpie, cross-bill, siskin, bullfinch, goldfinch, buzzard, and grebe. Owls are common in the Skibo and Dnnrobin woods. The grey lag goose and whooper swan are winter visitants, The eider duck breeds at Eilanhoan (Loch Eriboll) and the goosander in Loch Shin.
The adder and the lizard are found all over the county, the slow worm and newt in the western parishes.
Salmon, charr, sea trout, and river trout occur in most of the lochs and streams. Among sea fishes large halibut are found off Cape Wrath, while cod, ling, plaice, turbot, and sole are everywhere abundant. Sand eels (lesser launce) are common in the tidal shoals and sandbanks. Crustaceans such as lobster, crab, and mussel abound along the rocky coasts in the north and west, while clam and cockle arc found at low tide on the sandy flats. The streams in the limestone country abound with the lower forms of crustacea. Whelks, limpets, mussels and other molluscs abound on the rocks lying between low and high water-mark.
Alpine vegetation on the higher mountains represents the flora of the period which followed the Ice Age. As the climate softened, the flora of the temperate regions gradually extended over the river valleys reaching to the lower hills while the arctic flora receded to the corries in the mountains. There are still found such arctic plants as Saxifrage oppositifolia, S. hypnoides, Luzula spicata, Cochlearia, Eriophorum angustifolium and Lycopodium alpinium. Among rarer plants in the higher mountains is Luzula arcuata, found on Ben More and Foinnebhein. In some spots arctic vegetation still occurs on the lower grounds and after a succession of cold seasons the upland flora creeps lower down the mountain sides. Eriophorum pubescens occurs near Oykell Bridge and Draba incana as well as Saxifrage oppositifolia in Farr and on the borders of Loch Eriboll. In many of the lochans of the western parishes are found the bulrush, the white water lily (Nymphaea alba), and the prickly twig rush (Cladium mariscum).
The limestones of Assynt and Durness yield a rich and characteristic vegetation including Scolopendrium vulgare and the filmy fern (Hymenophyllum wilsonii), which occurs near Inchnadamph, while Dryas octopetala occurs at Stronchrubie and Smoo.
The vegetation of the inland moors and uplands largely comprises heather (Calluna vulgaris), deer's hair moss (Pleocharis caespitosa) and cotton grass. At times patches of other plants occur to break the dreary uniformity of the moors. Near Loch Craggy in Assynt, for example, Anderson observed quantities of Carex unifiora; Ribes petraeum occurs at Rosehall, where also Pinguicula lusitanica and Drosera anglica abound, while in the low marshes of Oykellside occur Malaxis paludosa, Pilularia, Globulifera and Nymphaea alba. At Faraird Head Scilla verna and Primula scotica occur. Hieracium denticulatum flourishes near Oykell Bridge.
Most of the woodlands of Sutherland grow in boulder clay overlying Old Red Sandstone. Scots pine, larch, and spruce prevail but there is also a considerable wood of oak and beech between Spinningdale and Creich and some fine deciduous trees at Skibo and Ospisdale. The richness of the secondary soils of the Dunrobin district accounts for the luxuriance of the vegetation. Though Dunrobin gardens lie close to the sea, yet even in Sir Robert Gordon's time there were "all kynds of froots, hearbs and floors, used in this Kingdom, and abundance of good saphron, tabacco and rosemarie".