Seal fun facts

We get a lot of questions about seals that can be about anything. From why gray puppies are white to whether a seal drinks salt water. We are always happy to answer these questions and therefore there are many nice seal facts that we have collected for you and that you can find here.

seals herringAll seals that are being rehabilitated and recover, are released back into their natural habitat. Because they are wild animals, we try to keep the rehabilitation period as short as possible. The shorter they are with us, the better it is for them. The seals we take care of are often underweight and weakened due to sickness or injuries. It is important that the nutrition we give them ensures that they regain their strength quickly. This requires a diet with a lot of fat. Herring is a fish that contains it in large quantities. The herring that we feed is defrosted fish.

In nature a seal hunts life fish and is not used tof rozen and immobile fishes. Therefore it may take a while before a seal eats the fish by itself. We always give the animal the opportunity to eat by itself, if it doesn’t, we feed it by hand. Herring is a smooth and firm fish which makes it easy to feed. A seal in the last phase (phase 3) of rehabilitation eats an average of about 5 kilos of herring per day.

seals in winterSome marine mammals can keep half of their brains awake while the other half is asleep, but seals have retained the bihemispheric sleep of their terrestrial ancestors. Difficult words, but it means that species like grey and harbour seals have to "turn off" their brains completely in order to sleep (just like dogs or humans), and it happens regardless of whether they sleep on land or in water.

However, very little is known about the sleep duration in seals. For example, a seal that sleeps underwater will need to wake up regularly to surface so that it can breathe. That makes it difficult to study their sleeping habits. A study observing 3 to 5 month old harp seals showed that they slept on land for an average of 6 hours a day, while adult caspian seals slept for about 4 hours a day.

seals in winterEspecially in winter we are often asked whether the seals swim in heated water. The answer is actually quite logical: no. Because when they swim in the sea, the water is not heated either. Seals can withstand very low temperatures due to a thick layer of fat under their fur.

This layer protects them from the cold and ensures that they keep their body at a good temperature even in very freezing weather. Seals build up this fat layer by eating well, it is a fat reserve. A very young puppy or a weakened animal has little or no reserves. Then we do use floorheating that is available in the intensive care units. There are also a few phase 2 outdoor pools with heat lamps for the seals to lie under. In both cases, we only use this heating when animals are very vulnerable and it is important that they rebuild reserves without using energy to stay warm.

witte pup The beautiful white fur of the grey seal pups is also called lanugo. It is a baby coat, intended to keep the body warm during the period when the puppy has yet to develop a thick layer of fat that will keep it warm as an adult seal. Until then, the lanugo protects the puppy from the cold on the land. So it is really just a very thick winter coat.

Grey seals are found in the northern hemisphere, also in areas much colder than the Netherlands and there the white color of the lanugo has another important function: it camouflages the pup in the snow. This allows them to remain safely on land for the first weeks of their lives without being noticed by predators.

drinkenzeehondenSeals never actually drink. Their kidneys can handle salt water, but they get the moisture they need from their food. Fish and crustaceans largely consist of water, which gives a seal sufficient moisture. They can store excess fluid in their fat layer as a reserve or urinate it out.

If a seal is found weakened on the beach because the animal has not eaten anything for a while, it may also be dehydrated. That is dangerous. The seal will then receive ORS from us as soon as possible. ORS stands for Oral Rehyration Salts, it is a powder that dissolves in water and is administered through a tube in the throat. This allows the moisture balance to regain quickly. ORS is often given immediately at the place where the seal is found so that the animal feels a little better before it is transported to Pieterburen.