Behaviour
Grey seal, Isle of Skye
Grey seals are coastal mammals and live in large groups. When they are not in the water they are found on rocky ledges, beaches or on pack ice (Jefferson et al, 2008).
These haul out sites and are usually quiet areas very close to the water's edge, with good access to the open sea (Pomeroy et al, 2000).
The seals rely on haul out sites to rest, breed, moult and give birth.
Grey seals can dive down to 300 metres for up to 30 minutes, although they are more likely to dive for 1–10 minutes, with an average depth of 60 metres or less (Jefferson et al, 2008).
To rest in the sea, the animals position themselves vertically in the water column with their head poking out of the water (Jefferson et al, 2008). Off the British coasts and in the Baltic Sea, their journeys out to sea are usually less than 50km from their haul out sites and last 2–5 days (Sjöberg et al, 1995; McConnell et al, 1999).
Feeding
Grey seals use almost the whole water column to obtain their food - they feed from the ocean floor to the surface and in between. The seals even take seabirds. Their prey includes:
- whiting
- smelt
- skate
- lumpfish
- pollock
- cod
- haddock
- plaice
- salmon
- cephalapods
- molluscs (Jefferson et al, 2008)
Their food requirements depend on the size of the animal and the nutritional richness of the prey. It is estimated that on average, 7kg of cod or 4kg of sand eels per day are consumed (Special Committee on Seals (SCOS), 2009).
Up to 70 percent of the grey seals' diet can consist of sand eels (Perrin, 2009).
Individuals normally forage within 100km of their haul out site, but tracking has shown that they can feed up to several hundred kilometres away (SCOS, 2009).
