Body & Health

The seal is the perfect submarine – on land they are clumsy, but under water they are incredibly agile. They use their whiskers to hunt and can stay submerged for a long time. They can even sleep under water! There are a lot of differences between common seals and grey seals, like when their pups are born, what they eat and where they live.

Every now and again, Sealcentre Pieterburen will rehabilitate special seals. In January 2016, a melanistic grey seal (Halichoerus grypus) was brought into the centre. A mela-what-now? Melanistic. Melanism is the scientific term used to describe animals that are coloured completely black due to the overproduction of the pigment melanin. In this article you can read all about melanism, if it hurts the animal and why we don’t see it very often in seals.

In the Netherlands, seals are mostly known for the “criers” when it comes to the sounds they make. Aside from the fact that the term “crying” gives the wrong impression of the sound seal pups make, older seals also produce sounds. What most people don’t know is that seals can imitate sounds they hear and even mimic words!

The sounds made by seal pups during their nursing period are very distinctive. In Dutch we started calling these sounds “crying”, and the pups who make the sound “criers”, especially if the pups in question have seemingly lost their mother. But pups don’t necessarily make these sounds from distress or fear. The sound they make likely has the important function to distinguish the hungry seal pups from one another in a large group. They are certainly not as helpless as, say, a crying baby. You can hear what seals sound like here:

When you see a seal swimming under water, you will see an animal that is completely in its element. Not only are they fast and agile swimmers, they can also stay submerged for a long time. Thanks to special adaptations in their bodies, they can stay under water for up to half an hour!

Just like all mammals, seals must breathe air to obtain the oxygen they need. That is why a seal cannot stay under water indefinitely – they will need to surface at some point. They are however, perfectly suited to life aquatic. Over time, their ancestors’ paws became flippers and their bodies sleek and flexible so they could swim at high speeds to hunt for fish. They also have adaptations inside their bodies: enlarged lungs, an enormous amount of red blood cells, and special pockets in the liver that can store oxygen-rich blood.

In its first year of life, a seal is susceptible to infection by lung worms. After being weaned, young seals will go out and start hunting for prey by themselves. This is when they often contract lung worm infections. A number of them will get so sick, that they would not be able to survive without help. Lung worms are parasites that can severely damage the lungs – they eat the tissues in the lungs and reproduce there, causing more and more damage in the process.

All about grey men, blonde ladies and white seal pups
When winter is quickly approaching it means that for many, it is time to turn up the thermostat or throw some extra wood in the fireplace. Nice and cosy; indoors and out of the rain, hail, and first snowflakes. For the grey seal, life looks very different. To them, this time of year means female seals birthing and caring for their white seal pups, come rain or shine. And the males? They will be on the lookout to win over the females.