position and arrangement of the nostrils are also diagnostic features distinguishing grey from common seals. In the latter the two nostrils almost meet at their most anterior and ventral point and diverge above this at a distinct angle. In the grey seal the nostrils are almost parallel and their anterior ventral points are separated by a large pad of skin (Fig. 11).
The grey seal is highly vocal, particularly the cow. All aggression by cows, if only jostling for position in a haul-out, is accompanied by high-pitched hooting which has a peculiar quavering quality, partly of pitch and partly of volume. This hooting often carried out by several cows at once produces a weird sound which has been called ‘singing’ but it is far from singing at its best! The bulls are capable of a snarling hiss which also has a guttural quality. However, often in mild aggression they do no more than open their mouths and emit an exhalation which is almost soundless. The high pitched voice of the pup is described later (See here).
There are many parts of Britain where the species of seal present can be almost certainly determined by the habitat. Thus, as Fraser Darling has said, the common seal on the west coast of Scotland is a sea-loch seal, the grey a seal of the outer islands and the strong Atlantic seas. And again on the Essex coast the mud and sand flats are typical haul-out sites for common seals, while the rock-bound coasts of west Wales provide typical grounds for the grey. Nevertheless it is not possible to generalise completely. Certainly the grey seal uses habitats which would rarely be used by common seals, isolated skerries and islands swept by Atlantic gales and surrounded by tidal rips which throw the sea into tumultuous heaps. The common seal will use estuarine waters and the mud and sand banks associated with them where the grey would never go. Yet between these extremes there are many habitats which both use. Many of the haul-outs in Orkney and Shetland are mixed, although of course the breeding grounds never are.
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