The difference between a common and a grey seal.

Reading time 4 minutes · Part of: Knowledge base

The short answer

The common seal has a round "dog-like" head, a short snout and V-shaped nostrils. The grey seal is larger, with an elongated cone-shaped head, a flat snout and parallel nostrils. The table below summarises the five most useful features; we explain each point afterwards.

1. The head: round versus cone

By far the quickest identifier is the shape of the head. A common seal has a head you can describe, with some imagination, "like a wet labrador": short, round and with large eyes set high on the skull. The grey seal, by contrast, has a cone-shaped head with a flat forehead running in one straight line into the snout. Hence the Latin name Halichoerus grypus — "hook-nosed sea pig".

In adult grey males (bulls) the head is also thicker and more muscular than in females, with a pronounced neck fold. Females have a finer cone.

2. The snout: short versus long

The snout is the direct extension of the head shape. In the common seal it is short and tipped slightly upward, as if the animal is curiously sniffing something. In the grey seal the snout is long, straight and flat — comparable to that of a horse or donkey. From the side you can see the profile has almost no kink between forehead and nose.

3. The nostrils: V versus parallel

When a seal pokes its head above water to look you over, look at the nostrils. In the common seal they touch at the bottom and together form a clear V. In the grey seal the nostrils stand almost vertical and parallel, like two separate slits with visible space between them. This is one of the most reliable features at a distance with binoculars.

4. The weight: half a car versus a whole one

An adult male common seal weighs 80 to 110 kilograms and reaches about 1.5 to 1.8 metres in length. A male grey seal is a different category: 230 to 300 kilos, sometimes up to 2.5 metres. On a sandbar the size difference is immediately obvious — especially when they lie side by side. Females of both species are slightly smaller than the males, but the difference between species remains large: a grey female still weighs 100–180 kg.

5. The pups: spotted versus white

The clearest differences are seen in the nursery. A common seal pup is born in June or July, has the spotted adult coat immediately, and can swim within an hour. A grey seal pup is born between November and January with a white downy coat (lanugo) and stays on land for three weeks while the mother fattens it on extremely rich milk (60% fat). Only after moulting does the pup enter the sea.

For the full biological and historical context of both species, see our extensive overview The difference between the species, or the individual profiles of the common seal and the grey seal. For anatomical details (skeleton, vibrissae, eyes) you can go to seal anatomy.