Anyone travelling through the Wadden Sea this summer will see them: Seals on sandbanks, lolling in the sun, curious snouts peeking out of the water. But what looks like an untroubled idyll is actually an ecosystem in upheaval. While grey seals are experiencing an unprecedented renaissance and now live in their thousands in the German Wadden Sea, the seal population is stagnating despite record numbers of pups. Scientists are faced with a puzzle, and for recreational boaters the current situation means one thing above all: increased vigilance in the coming weeks. This is because more than 7,000 harbour seals will be born between the beginning of June and mid-July - and any disturbance can be life-threatening for the pups. An overview of the situation in the UNESCO World Heritage Site.
The return of the giants
It is one of the biggest and least known success stories of German species conservation: grey seals were practically extinct in this country a hundred years ago - hunted and driven away. Today, around 12,000 of these impressive animals are once again roaming the Wadden Sea and the North Sea between the Netherlands and Denmark. In the Lower Saxony part of the UNESCO World Heritage Site alone, a total of 1,692 grey seals were counted in the winter of 2025/26, including 575 pups - 136 more than in the previous year. These are record numbers.
Heligoland has become a German grey seal stronghold. Baby seals have been born here again since 1996 and the numbers are increasing year on year. Last winter season, there were 971 pups and, according to the municipality of Heligoland, the magic mark of 1,000 is likely to have been broken for the first time in the 2024/25 season. Visitors to the high seas island in winter in particular are treated to a unique spectacle: white seal pups with big saucer eyes lying on the dune while their mothers hunt for fish in the water.
The second most important area for grey seals is the Kachelotplate between Juist and Borkum. This huge sandbank, around 70 football pitches in size, is strictly protected and may not be entered. This is exactly what makes it so attractive for the seals: no people, no disturbance, plenty of food.
The seal paradox
While grey seals are experiencing a real baby boom, the picture is different for harbour seals. In the summer of 2025, more than 10,000 seal pups were counted throughout the Wadden Sea - an increase of 22 per cent compared to the previous year. Actually a reason to celebrate. If it weren't for the overall figures: Only just under 24,000 adult animals were recorded, just one per cent more than in 2024.
There are major regional differences. In the Netherlands, both the number of puppies and the total number of dogs rose sharply. In Denmark, on the other hand, the population fell by 20 per cent and in Schleswig-Holstein by eight per cent. What is going wrong here? The Common Wadden Sea Secretariat - the joint coordination centre of the three Wadden Sea countries, CWSS - suspects that many young animals will not survive the critical phase. Climate change, fluctuating fish stocks, more time spent in the water looking for food - all of this costs energy. However, it is also possible that the animals are simply travelling more frequently and are therefore less likely to be counted from the aircraft. Nobody knows for sure. In Germany, the picture is mixed, but on Heligoland, harbour seals hardly play a role - just two pups were counted. The island belongs to the grey seals.
When seals prey on seals
For a long time, scientists thought that grey seals fed exclusively on fish. Then, a good ten years ago, dead seals with strange injuries were repeatedly found on German and British coasts. Ship propellers were suspected to be the cause. Until 2013, when what no one had previously thought possible was documented for the first time: grey seals were hunting seals.
It is now clear that the large seals are apex predators that not only eat fish, but also seals, harbour porpoises and even their own kind. Researchers at the University of Veterinary Medicine Hannover have been studying their hunting behaviour for six years. They observed how grey seals kill their prey and eat the fat piece by piece for up to 90 minutes. A brutal, but completely natural behaviour.
Is this the reason for the seal decline? It may play a role, but the situation is more complex. Competition for food, habitat degradation, noise pollution, environmental toxins - all of these factors work together. Incidentally, it is interesting to look back: in the Middle Ages, grey seals and harbour seals were roughly equally common, and grey seals may even have dominated. What we are experiencing today could therefore be a return to natural conditions.
Who's turning up?
Harbour seal or grey seal? It's not that difficult to tell the difference from the boat - the head gives it all away: harbour seals have a rounded head shape with V-shaped nostrils that are close together. Grey seals, on the other hand, have an elongated "horse nose" with parallel nostrils - particularly pronounced in the males.
Harbour seals are also smaller and slimmer than grey seals, whose males can be more than two metres long and weigh up to 330 kilograms. This makes them the largest predator in Germany, with a set of teeth like a brown bear.
There is another difference in the fur: seals are dark grey on the back with many spots, the belly is light. In grey seals, you can clearly see the difference between the sexes - males are dark with light spots, females are light with dark spots. The pups are particularly easy to recognise: Grey seal pups are born in winter with white fur, harbour seal pups in summer are already spotted.
The best spots to watch seals
Heligoland is the undisputed number one destination for anyone who wants to see grey seals. November to January is peak season, when the white seal pups are born. But a visit is also worthwhile in summer, as the animals lie on the dune all year round and some are even on the main island near the dune. The Kachelotplate between Juist and Borkum is the second hotspot, but can only be admired from the water. It is strictly forbidden to enter as it belongs to the quiet zone of the national park.
The majority of seal pups are born in June and July. At low tide, the seals retreat to the sandbanks - this is the best time for observations, but also the most sensitive. Early in the morning or late in the afternoon you have the best chances. In places, the mudflat paths pass very close to the seal banks.
However, anyone travelling in the Wadden Sea should adhere to a few simple rules. A distance of 300 metres from seal resting places is mandatory, not only for legal reasons, but also because the animals will otherwise flee into the water. A study has shown that only around one in five seals return to their resting place within the same tidal period if they have been disturbed. This can lead to a critical loss of energy for nursing mothers and pups. If you pass close to the seal beds when passing the islands, sudden noises and fast manoeuvres should be avoided as far as possible. And very important: always drive past a group of seals from the side, never directly towards them.
Certain things are completely taboo: sandbank landings near seal moorings, anchoring in protected areas, high speeds in shallow mudflats. SUP boards and kayaks are also treacherous because they approach very quietly and can frighten the animals.
Ursula Meer
Redakteurin Panorama und Reise
