These large mammals live a good life in the Wadden Sea. The area not only provides a well-stocked pantry for the seals, it also provides them with a safe place to rest and breed.
By far the majority of the seals in the Wadden Sea are harbour seals, however you may also be lucky enough to spot a large grey seal. The harbour seals especially use the banks of the Wadden Sea to rest and to recover after having given birth to their young in the summer. For the first three to four weeks of the pups’ life, the mother suckles her young. After this initial period, they have to learn to catch their own food. Over the past 10-20 years, the grey seal has become more common in the Wadden Sea, and in December 2014 a grey seal pup was spotted during the seal census by the Fisheries and Maritime Museum. This established that, for the first time since the 1500s, the grey seal were breeding again in the Danish part of the Wadden Sea. A grey seal pup was seen languishing in the sun with its mother on a sandbank near Rømø.
Seals are predators and are thus related to wolves and bears, for example. It is believed that the seals’ closest living relative is a marten-like animal. The harbour seal usually grows to 1.3-1.6 m long and can weigh up to 130 kg. The grey seal is significantly larger, and with its 300 kg, it is not just Denmark’s largest predator, it is also Denmark's largest mammal.
The seal has evolved over several million years from being a land-based creature to spending a large part of its life in the water.
The seal’s torpedo-shaped body and its broad flippers make it an adept swimmer, and its thick layer of blubber protects it from the cold. Its big eyes, which are very sensitive to light, enable the seal to see under the water, and its whiskers help it sense even the smallest movements from fish. Seals can easily stay under water for several minutes, because their large bodies store and save oxygen. However, they still need to seek land every now and then. It can sleep in the water, but in order to rest properly, it must be on land. This is why you often see seals lying on the sand banks in the Wadden Sea.
The seal population in Denmark has been hit by seal plague twice, once in 1988 and once in 2002. On both occasions approximately 50-60% of the population was wiped out. Seal plague is a virus that attacks the seal’s immune system and leaves the animal susceptible to bacteria-borne infections. Consequently, most of the seals that died during the seal plague epidemic died of pneumonia.
During the period when the young harbour seal suckles from its mother, a pup sometimes gets lost. The pup is in dire straights without its mother, and it climbs onto the beach and calls out for her. These young ‘howlers’, as they are known, cannot survive without their mothers and they are put down to prevent any unnecessary suffering.
Germany and the Netherlands have several centres that care for howlers before they are released into the wild. However, this practice was discontinued in Denmark in 1995 because at that time the seal population was substantial and healthy. Moreover, releasing howlers is not entirely without its problems. This is why Denmark’s seal management efforts aim to minimise human interference. In late summer and autumn in particular you might see a sick seal that has climbed onto land to keep warm. If you do see a howler or a sick seal, you should leave it alone and contact the Danish Nature Agency or the Fisheries and Maritime Museum.
The Wadden Sea is a good place to experience seals first hand. If you want to get really close to the seals, the sealarium at the Fisheries and Maritime Museum in Esbjerg is a good choice. Through the big underwater windows, you can see harbour seals and grey seals as they gracefully glide through the water. At the two daily feeding sessions, you can also learn more about the life and biology of the seals. Moreover, you can experience the seals in the wild at a distance. Seals are shy animals, so it might be a good idea to bring along some binoculars sothat you can see them better. You can book a nature interpreter to take you on a trip to the seal banks.