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.
Source: Irish Naturism Association
Original publication 15 February, 2021
Posted on NatCorn 26th February 2021
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