Seals are part of a group of mammals known as pinnipeds which translates as “winged footed”. They are called this as they have paddled shaped rear flippers to help move them along in the water along with undulating movements. Almost weightless in the water due to their body composition, they swim with great speed and are highly agile in water. As water has a higher density to air they have evolved with relatively short but powerful appendages for their size. These adapted pentadactyl limbs have 5 digits, commonly seen in vertebrates and it is thought that they evolved from an otter type mammal around 18 million year ago.
This means that we share a common ancestor as we to have pentadactyl limbs on our hands and feet which makes them all the more interesting and relatable and reminds us to think ourselves not so separate to the natural world. This idea holistically integrates us as another species that has evolved on planet earth. Rather than looking at humanity’s existence as anthropocentric, the idea of this shared pentadactyl limb roots us more centrally in bio-centric thinking, ecologically. Humankind being Man of nature rather than Man “in” nature.
So, without further delay, let’s look at our cousins!
Seals are Pinnipeds and can be divided into 3 distinct categories: True Seals (phocids), Eared Seals (otariids) and Walruses (dobenids).
Both common seals (harbour) and grey seals are known as true seals. Both lack external ears and are more suited to water than land, although inhabit and need both. On land they tend to move about quite awkwardly, using their bodies to bounce and shift not having the ability to use their front limbs or tilt their pelvis to aid movement like an eared seal or walrus can. In the ocean they spend 80 % of their time under water and 20% at the surface rebalancing the complex chemistry within them that changes to enable long deep dives of 10 minutes+, typically at 80m extending to 200m or more. On deeper dives the heart rate can slow to fewer than 20 beats a minute and blood flow is limited in non-essential areas. Hunting dives typically have the soundtrack of pronounced series of clicking. It is thought that it could be a form of echolocation to find prey. Hunting dives typically last only 10 min and are performed in not more than 100m of shallow water. During the dive seals relying on oxygen that has been stored in their muscles and blood vessels. Through an adapted vascular system their bodies also store twice the amount of blood normally found in terrestrial mammals of similar size. They have seemingly a high ability to cope with lactic acid build up to which is good, as there nostrils seemingly are generally closed at rest! Their bodies appear chunky, pups should look like round potatoes which indicates a healthy seal as does dark patches around the eyes, as they are moist and healthy. If a young seal looks in any way thin, or his eyes have no watery marks around them, it is safe to assume he may be poorly. Seals have sharp teeth and claws of approximately 3cm at the end of each digit. It is recommended not to approach the seal too closely (50 meters gap) as this action may drive a pup or adult cow or bull into the water to hide when what it really needed to do is rest. This is especially true and precarious in the first 3 weeks as pup have not yet blown their white birth coat, which is not waterproof! Although some shed this white coat in uterio, ready to make sea visits almost immediately. Grey seals have keen eyesight both on land and under water which are large and forward facing. They can submerge for long periods of time and when visibility is poor due to poor light or sediment they can depend on directional hearing organs and vibrissae which are the sensitive whiskers that are present on the muzzle.
Seals are covered with short thick fur and can grow up to 2 m long weighing up to 375lbs., the male or bull growing larger and generally look darker than the female – although they all look fairly dark when wet. Grey seal females can live up to 40 years old while bulls tend to only make it to 25. Females are sexually mature at 4 and are capable of reproduction. Males are capable and fully grown at 6 but it is said that they will not have acquired the necessary mass and power to become a dominate bull until 10 years old. Globally there are 3 main groups of grey seals. Map is approximate only.
We shall focus on the Eastern Atlantic grey seal group indigenous generally to Ireland and Britain
GREY SEAL IDENTIFICATION
Scientific Name: Halichoerus Grypus
Higher Classification: Halichoerus
Species: H. Grypus
Cow-smaller, more slender muzzle, flatter head profile than male, generally darker patches and spots than the male with generally more grey colouration on the back and slighter still on the underside. Eyes will be further away from the muzzle and the top head shape will be aquiline in definition.
Bull- Thicker Muscular neck flowing through to shoulders, with a flat elongated head and straight parallel nostrils. Eyes and top head shape will remain the same for both sexes.
Track markings: similar to common seal but noticeably wider.
Vocal communication: More vocal than common seals. Underwater-Grunts and snorting androars Terrestrial- Wide range of social calls. Growling, hisses, barking, snarls, they also slap the water.
Preferred habitat: Rocky coastline, steep sand banks on the southern and western seaboard.
Mating: Sea caves, remote & beaches called rookeries containing several hundred seals.
Feeding: Opportunistic carnivorous -From the sea floor to the surface and beyond – feeding at many levels of sea depth, fasting intermittently. Diet consists of lobster, crabs, urchins, flatfish, crustaceans from the sea floor to an array of fish readily available including faster moving species like cod, herring, whiting, and sand eels, skate and mackerel. They reportedly snack on unsuspecting water fowl to!
Reproduction: Mating on land in large gatherings from August to November. Bulls will remain on land and forgoes hunting until the season lasting 8 weeks is over. The dominate bull can cover as much as 10 cows or more at the rookery site. Bulls become aggressive and territorial in breeding sites which are returned to yearly by both.
Gestation: True gestation of the pup lasts 8 .5 months however the cow can delay gestation of the foetus for up to 3 months if deliver conditions seem unfavourable on land. The cow returns to the breeding site to give birth to a single pup in early winter/ autumn.
Paternal care: The female gives birth to her pup and once weaned breeds again. She will leave to protect her newly born pup saving it from the male’s aggression and having becomeintolerant to of the other cows. Paternal care consists of feeding every 6 hours for 3 weeks during which time the pup should gain up to 2kg per day. She will generally not feed until the pup can hunt and fend for itself. Happy healthy pups and adults like to lay posed in an upward c shape when they are relaxed and feeling unthreatened.
WE HOPE THIS ARTICLE WAS HELPFUL TO UNDERSTAND MORE ABOUT OUR FURRY FRIENDS OF THE SEA.