How to identify grey and common seals

How can you tell the difference between a grey seal and a common seal, especially when you only get a brief look? We reveal what to look for and the behaviour you're most likely to see.

Grey seal (Halichoerus grypus) pup covering its face with one of its flippers on the beach. © Marcos G Meider/Getty

Only common seals (aka harbour seals) 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.

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Grey seal (Halichoerus grypus) pup lying on beach, close-up
Grey seal pup on the beach. © Andy Rouse/Getty

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). 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.

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.

Harbour seal sat on a rock in the bay of Plockton, in the Scottish Highlands. Also known as harbor seal or common seal
Common seal hauled out on a rocky shoreline in the Scottish Highlands. © Richard Stelmach/Getty

Common seals and grey seals (or gray seals) also both occur in North America, in both the US and Canada, so the same rules for identifying the species are useful for our American friends as well.

HOW TO TELL A COMMON SEAL FROM A GREY SEAL

1

Grey seals are larger than common seals

The common seal (pictured above) is up to 1.7 metres long, the grey 2.5 metres (pictured below). Colour is not a good guide to identification, especially as a seal’s colour changes as it dries out. Spots on common seals tend to be smaller and more numerous.

Grey Seal (Halichoerus grypus) pair playing on beach, Donna Nook, Lincolnshire, England
Grey seal pair playing on the beach. © Guy Edwardes/Getty
2

Common seals have a distinctive posture

The two seal 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 seal pup on the beach as part of the seal colony at Horsey, Norfolk, UK
Common seal pup showing the distinctive resting posture often adopted by common seals. © Ian Sherriffs/Getty
3

Common seals need their space

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.

Harbour seal aka common seal (Phoca vitulina) in the water.
Common seals have shorter faces and a somewhat friendlier look than grey seals. © Natalia Bubochkina/Getty
4

How to identify grey and common seals in the water

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 with pup (Halichoerus grypus)
Grey seal with pup. © Westend61/Getty

TYPICAL SEAL BEHAVIOUR TO WATCH OUT FOR

Playing seals

  • 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.
Grey seals swimming up close to a diver
It’s not unusual for curious seals to play with snorkellers and divers. These are grey seals. © Bernard Radvaner/Getty

Seal breeding behaviour

  • 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.
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Common seal aka harbour seal (Phoca vitulina)
Common seal diving in a kelp forest. © Douglas Klug/Getty

Raising seal 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.
Common seal pup laughing on the beach in Germany
Common seal pup laughing on the beach. © Westend61/Getty