How to identify British seals

Seeing a seal is very exciting, but can you tell the difference between a grey seal and a common seal? We reveal what to look for – and the behaviour you are most likely to see.

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Common seal, UK.

While seals can be seen basking at any time of year, they primarily return to land to moult (common seals from August to September; grey seals from February to April) and breed (common seals from June to August; grey seals from September to December).

Because seals hunt in the open sea and usually travel long distances in search of prey, returning to land imposes a significant drain on their energy reserves. So they tend to fast when ashore and minimise the time they spend on land.

 
HOW TO TELL A COMMON SEAL FROM A GREY SEAL:
 
  • Only common and grey seals breed in British waters, though vagrant northern seals (ringed, harp, hooded and bearded seals and walruses) can be seen around our coasts.
     
  • The common seal (pictured above) is up to 1.7 metres long, the grey 2.5 metres (pictured below). Colour is not a guide to identification and changes as the seals dry out. Spots on common seals tend to be smaller and more numerous.
     
  • The species may haul out together. One quick way to tell them apart is that on land, common seals often adopt a characteristic ‘head-up, tail-up’ posture.
     
  • Common seals tend to be more spread out than greys when hauled out. They use aggressive behaviours such as headbutting, growling, biting and waving fore-flippers to maintain individual space.
     
  • Blubber is a good insulator at sea, but seals can overheat on land, even on cool days, so they often fan themselves with their flippers. Hauling out on wet sand also helps them to keep cool.
     
  • Common and grey seals are difficult to tell apart when in the water. The common seal has a relatively smaller head and concave forehead, and its nostrils form a V-shape. The grey seal has an elongated ‘Roman nose’ and its nostrils are parallel (they don’t meet at the bottom).

 

Grey seal © MikeLane45/iStock 
 
TYPICAL SEAL BEHAVIOUR TO WATCH OUT FOR:
 
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  • Seals often frolic with floats on fishing nets or lobster pots. They may become entangled and many drown. Seals can also cause damage to nets and fish farms when trying to steal fish.
  • An adult seal’s heart rate varies from 55 to 120 beats a minute. On diving, it slows to 4 to 15 beats, so it can hunt underwater for half an hour.
 
Breeding
  • Seals breed at traditional rookeries – usually remote offshore islands, sea caves or inaccessible beaches where pups are safe from predators.
  • Seals mate shortly after giving birth. The fertilised egg floats freely in the uterus and is not implanted for two to three months.
  • Common seals usually mate in the water. Grey seal bulls gather harems inland when on islands.
 
Raising pups
  • Common seal pups are born in intertidal areas or at sea. They have adult coats and can swim and dive from birth. A mother may play with her pup or even carry it on her back. Grey seal pups are born on land, have long white coats and do not enter the water until they moult around weaning time.
  • Pups of both species are fed for up to four weeks, during which time they can more than double their weight. Their mothers then abandon them.
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