animal Many young seals live in the Wadden Sea, according to a study
The number of seals in the Wadden Sea and on Heligoland is decreasing in the long term. At the same time, an unusually high number of pups has been observed.
15.11.2025, 04:45
SDA
This is the conclusion reached by a trilateral group of experts on marine mammals in their report "Census of seals in the Wadden Sea 2025". Researchers and administrative staff from Denmark, Germany and the Netherlands were involved in the project.
Overall, the number of seals has decreased over the past ten years - at the same time, the proportion of young animals in the total population continues to increase, according to the report. "The figures could indicate a higher proportion of pregnant females in the total population with a simultaneous increase in pup mortality. This would mean that fewer young animals are reaching adulthood overall," says Anders Galatius, lead author of the report and senior researcher at the Institute of Ecoscience at Aarhus University, according to the press release.
Another or additional explanation could be that there are fewer animals on the sandbanks during the moulting period. However, both assumptions are preliminary - further research is needed to understand the causes of this phenomenon
Tourists disturb young animals and mothers
During the summer months of June to September - when seals give birth and raise their young - they need peace and quiet, explains the Norddeich Seal Station (Aurich district). "During these months, however, there are numerous tourists in the Wadden Sea who disturb the seals through activities such as careless mudflat walks, water sports or incorrect behavior." Some experts consider human disturbance to be the most common cause of separation between mother and pup, the station writes on its website.
These disturbances can have fatal consequences for young seals. If the seal mothers are interrupted while suckling, for example, the pups can become underweight and even die from lack of food or freezing to death. If the animals have to flee because tourists are too close to a protection zone, they consume energy, which they also lack due to a lack of suckling.
In addition, large wounds, navel perforations or even fatal peritonitis can occur in young animals whose navels are still open due to the friction on the sand during the seal hunt.
Regional differences in the numbers
The total number of 23,954 seals counted in Schleswig-Holstein, Lower Saxony, Hamburg, the Netherlands and Denmark in August 2025 represents a slight increase of one percent compared to the previous year. "However, as with the counts from 2022 to 2024, this figure is still below all surveys from 2012 to 2021," the research report states. This could indicate a stabilization of the population at a lower level.
The regional developments vary: Numbers fell in Denmark and Schleswig-Holstein. In Lower Saxony, Hamburg, on Heligoland and in the Netherlands, the number had risen according to the census.
After comparatively low numbers of young animals in the years 2022 to 2024, the 2025 surveys recorded the second-highest absolute number of young animals since the start of cross-border censuses. A total of 10,044 pups were counted - an increase of 22 percent compared to 2024. Here too, as with the pups, there are regional differences.
Harbor seals are a protected species
As part of the monitoring of the trilateral Wadden Sea cooperation, the expert group for marine mammals coordinates the counts and collates the data from the entire Wadden Sea region. Harbor seals are trilaterally protected by an agreement on the conservation of harbor seals in the Wadden Sea under the auspices of the UN Convention on the Conservation of Migratory Species of Wild Animals (CMS).
