Common seal — Phoca vitulina

The short profile

The common seal (Phoca vitulina), also called the harbour seal, is by far the most frequently seen seal along the Dutch coast. It is a medium-sized true seal in the family Phocidae, specialised in coastal waters of the northern hemisphere. In the Netherlands you'll find it from Texel down to the Westerschelde, almost always within fifty kilometres of the coast and preferably on a shallow sandbar that dries out at low tide. Anyone who has looked at one carefully will spot it again easily: a short, "cat-like" snout, large dark eyes and a sleek, mottled body that looks ungainly on land but moves with extraordinary agility under water.

• HeadRound, "cat-like"
• SnoutShort, blunt
• NostrilsV-shaped, meeting at the bottom
• Length1.3–1.9 m
• Weight65–130 kg
• Lifespan25–35 years (females often older)
• Pup seasonJune–July
• Feeding typeCarnivore — mainly fish

How to recognise a common seal

The strongest field mark is the shape of the head. The common seal has a strikingly round head with a short, snub-nosed snout — a silhouette that reminds many people of a dog or a cat. The forehead rises steeply and flows into the snout without an obvious break. The large, round, dark eyes reinforce the "sweet" impression.

The second feature is the nostrils. On the common seal they form a clear V: the two openings nearly touch at the bottom centre and splay apart towards the top. On the grey seal they run almost parallel. With binoculars and a quiet animal, that difference is easy to read from the sandbar.

The coat is variable, but adults typically show a silver-grey to greyish-brown base colour with irregular dark spots and rings. The belly is usually lighter. Coat alone is not a reliable feature — there are both dark and pale common seals — but combined with the round head and smaller size it provides a first cue. Adult common seals weigh between 65 and 130 kg and measure 1.3 to 1.9 m. Females are slightly smaller than males.

Habitat in the Netherlands

The common seal is a true coastal species. It thrives in shallow seas with strong tidal ranges and extensive intertidal flats. The Waddenzee is therefore its main Dutch stronghold: from the Razende Bol off Texel to the Eems near Rottumeroog, dozens of haul-out sites are scattered along the coast, with large concentrations around Vlieland, Terschelling, Ameland and in the Eems-Dollard. The Zeeland Delta — chiefly the Oosterschelde and the mouth of the Westerschelde — has also held a growing population since the 1980s. The occasional individual even swims up the Nieuwe Waterweg or turns up in the IJsselmeer.

Foraging trips generally stay within fifty kilometres of the haul-out site. The common seal is no ocean wanderer: it shuttles between the sandbar where it rests and moults, and the slightly deeper channels where it hunts.

Diet & hunting

The common seal is an opportunistic fish-eater. The menu features mainly flatfish (plaice, flounder, dab, sole), cod relatives (cod, whiting, bib), sandeel, herring and — especially in summer — shrimp. What it eats depends strongly on season and location: in the western Waddenzee flatfish dominate, while in the Oosterschelde gobies and shrimp turn up more often.

An adult animal needs roughly 3 to 5 kg of fish per day. It catches prey mostly on or just above the seabed, using a combination of sight, hearing and — in turbid water — the extremely sensitive whiskers that pick up minute changes in the water flow. Most dives are shallow (ten to thirty metres) and short (two to five minutes), but physiologically the species can reach around 200 m and stay submerged for almost half an hour.

Reproduction

The common seal is a summer pupper. Between mid-June and late July, females give birth to a single pup on an exposed sandbar. At birth the pup already wears its adult coat — the white lanugo has been shed in the womb — and it can follow its mother into the water within hours. That ability is essential: at high tide the birth site is usually submerged, and any pup that cannot swim drowns.

The nursing period lasts three to four weeks. In that short window the pup quadruples its weight on milk of around 50% fat content. After that the mother breaks contact abruptly and the young must learn to hunt on its own — a critical phase with high mortality. Females usually reach sexual maturity at four or five years, males a little later. Mating follows immediately after the end of nursing, and delayed implantation means the visible gestation again takes around eleven months.

Population and trend

The common seal never disappeared entirely from the Netherlands, but was severely reduced in the twentieth century by hunting, pollution and two viral epidemics (PDV in 1988 and 2002). After the 1962 hunting ban and the phase-out of PCBs the population recovered strongly. Between 1990 and 2013 numbers in the Waddenzee tripled.

Since 2013 the growth has stalled, and since 2022 a slight decline has been recorded. Surveyors and researchers point to a combination of factors: reduced flatfish availability as the Waddenzee warms, possible food competition with the rapidly growing grey seal, increasing recreational disturbance, and a bird-flu outbreak that also caused seal mortality in 2023–2024. Current counts can be found on counts.

Difference from the grey seal

On a Dutch sandbar both species often lie mixed together. Remember: round head, short snout, V-shaped nostrils, smaller = common seal; cone-shaped head, long snout, parallel nostrils, hefty = grey seal. Five practical identification points are listed on the difference between common and grey seal.

In the field: where to see them

The best places to see common seals are the tidal divides behind the Wadden islands and the sandbars in the Oosterschelde. Go at low tide, stay at least 300 metres away and use binoculars. Boat trips from Lauwersoog, Harlingen, Texel and Yerseke will reliably take you near haul-out sites without disturbing the animals. Plan your trip with the spotting guide and check exact haul-out locations on the spotting map.