Marine ecosystem
Why Seal are important
Ireland’s native seal populations areKeystone Species. They are VITAL to the Irish marine ecosystem. Seals have inhabited the Irish coastline for millennia playing a critical role in balancing the ecosystem and recycling nutrients. They are also a bio-indicator species. Researching issues or changes occurring in wild seal populations helps us to identify greater environmental issues, that we can strive to address. Worldwide, predators of seals include large shark species and killer whales. However, these large predators are no longer found in high numbers in Irish waters, therefore seals and cetaceans (whales and dolphins) reign as apex predators. As such they are considered ‘doctors’ of the marine ecosystem. The intricate predator-prey dynamics and processes of natural selection, result in apex predators removing weak individuals from prey populations, supporting a stronger evolution of species in the ocean.
Marine mammals
Pinnipeds Family
Seals belong to a group of mammals called Pinnipeds, which translates to ‘wing-footed’ in Latin, referring to their paddle-like flippers.
Pinnipeds can be grouped into three categories:
True Seals (Phocids), Eared Seals (Otariids) or Walruses(Odobenids).
Telling the diffrence
Ireland’s True Seals
Both of Ireland’s natives, the Grey and Common seals, are known as True Seals; they lack an external ear and simply have an opening on either side of the head. True seals are also slow and clumsy on land, using their bodies to bounce along the ground, whereas eared seals have a rotating pelvis which enables them to “walk” more easily on land, same as the walrus.
Walrus are the only remaining members of the Odobenids and are easily recognised by their characteristic tusks.
Discover the fascinating differences between seals and walruses. Explore their unique traits and contributions to marine ecosystems. Can you tell which is which ?
Quick facts
Grey Seals & Common Seal
Common Seals
Grey Seals
Marine Adaptations
Adaptations to Life in the Sea
Keeping warm
Grey and Common seals live scattered along our coastline. Grey seals like to roam around the North Atlantic during the year, travelling from one country to another but returning to the same place each year to breed and give birth.They are found on offshore islands and on rocky beaches and coves. Common seals travel far less, and can usually be seen in bays, estuaries and sheltered inlets. As they must spend large amounts of time on land resting and restoring energy reserves between swims, it is important for both species to have access to safe haul-out sites where they are protected from disturbance from humans and dogs.
Streamlining
‘True seals’ have specialised bodies shaped like torpedoes, with no obvious neck, no external ears or genitalia, and reduced limbs and tail allowing them to swim and manoeuvre quickly in water toe scape predators or catch prey. This body shape helps to reduce drag in the water which is 800 times denser than air. The streamlining is enhanced by the layer of blubber rounding off all bony protuberances.
Locomotion
Seals are often referred to as the ‘acrobats of the sea’ due to their agility in the water. They are able to swim effectively over very long distances achieving speeds of up to 25 knots! Their front flippers are used primarily for steering, while their hind flippers used for propulsion, are bound to the pelvis in such a way that they cannot bring them under their body to walk on them like fur seals or sea lions. However, as agile as they are underwater, they are very clumsy on land, having to bounce and wriggle with their front flippers and abdominal muscles. This makes them slow to escape and vulnerable on land.
Diving
Dives usually last 5 – 15 minutes and from 30– 70 metres. The nostrils are kept closed during dives and opened on surfacing. Only a very short recovery period is needed between dives. Seals exhale on diving and the lungs and alveoli collapse at a depth between 25 – 50 metres, thus pushing any residual air into non-absorptive air spaces. This prevents seals from suffering from buoyancy problems and any risk of the bends.
Coping with Salt
Seals restrict their seawater intake to avoid taking on excess salt. They primarily derive fluids from the food they consume, e.g. 90% of freshwater taken in by common seals is from the fish they eat and most of the remaining 10% is metabolic water and inspired water vapour. Seals kidneys are very efficient at concentrating urine. They produce urine that has a higher concentration of salt than seawater.
Vision
The eyes are large with a strengthened cornea adapted to the refractive index of water, and a retina adapted to dim light conditions, allowing good visibility underwater. They also have a protective third eyelid that wipes sand away and a continually produced tear film also helps to protect the eyes. On land, in brightly lit conditions, constriction of the pupil reduces the light intensity, which in turn reduces the refraction of light through the lens, allowing the eye to effectively focus.
Habitat
Grey and Common seals live scattered along our coastline. Grey seals like to roam around the North Atlantic during the year, travelling from one country to another but returning to the same place each year to breed and give birth. They are found on offshore islands and on rocky beaches and coves. Common seals travel far less, and can usually be seen in bays, estuaries and sheltered inlets. As they must spend large amounts of time on land resting and restoring energy reserves between swims, it is important for both species to have access to safe haul-out sites where they are protected from disturbance from humans and dogs.
Keeping warm
Grey and Common seals live scattered along our coastline. Grey seals like to roam around the North Atlantic during the year, travelling from one country to another but returning to the same place each year to breed and give birth.They are found on offshore islands and on rocky beaches and coves. Common seals travel far less, and can usually be seen in bays, estuaries and sheltered inlets. As they must spend large amounts of time on land resting and restoring energy reserves between swims, it is important for both species to have access to safe haul-out sites where they are protected from disturbance from humans and dogs.
