Seals
The Common Seal is a semi-aquatic Pinniped (fin-footed marine mammal). Seals have several families, including Odobenidae (walrus), Otariidae (eared seals, sea lions, fur seals), Phocidae (earless seals). The common seal is typically sleek-bodied and barrel-shaped with adaptive bodies to aquatic habitats where they spend most of their lives. They have short, wide flat flipper limbs that aid them in movement.
The Phocidae (Earless seals or “True Seals”) are the most diverse. They lack external ears, have streamlined snouts, and more aquatically adapted than the otariids swimming with efficient undulating body movements and relying on their rear flippers, but are very clumsy on land. The Otariids or “eared seals” or “sea lions” and “fur seals” are very vocal social animals better adapted to terrestrial habitats like rocks, beaches, and sea caves as their rear flippers can turn forward and they can move on all fours. They have external ears and more dog-like snouts.
The Walrus, or “Odobenidae” is larger than the sea lion or fur seal and has long tusks and very large bulky body. They too, like the Sea Lion, can turn their rear flippers forward but the way they swim is more like the true seal relying on sinuous whole body movements. They also lack external ears. Walruses feed on clams and other invertebrates on the ocean floor, while True Seals, fur seals, and sea lions depend on hunting fish and squid in the open ocean. The flippers are proportionally shorter than the external limbs, legs, and arms of other mammals as well as some flippers smaller than wings of birds and bats relative to body size. Each limb’s digits are bound together by a web of skin connecting the fingers and toes, and most have claws either on their front flippers (earless seals) or back flippers (eared seals). The Sea Lions nad Fur Seals have a specially adapted fur coat that includes outer guard hairs to repel water and insulating underfur as well as blubber to keep them warm in cold waters. Most of the pinnipeds annually molt their fur replacing worn fur and skin for a new coat. This process can compromise thermoregulation and temporarily ground them. Pups are often born with a natal coat of a different length, fur color, or texture than the adults have – this will change with age, and the coat is adapted for the terrestrial pre-weaning period. Until they develope their adult coat, the pups risk hypothermia and drowning with long exposures in the sea.
Pinniped lungs have airways with highly reinforced cartilage and smoth muscles that allow for their deep sea dives, the alveoli completely collapse during deep dives emptying the lungs completely. They can stay under for nearly 2 hours. They are able to re-inflate their lungs even after complete respiratory collapse. They are also very well adapted for seeing above and below the surface of the water in which they dwell. They have a clear membrane that covers and protects the eyes while underwater and the nostrils will close and stop blood circulation to most of its organs when diving. The whiskers help them navigate, and sensors in the skull allows them to absorb sound underwater and transit them to the cochlea. The fur seals, sea lions, and larger seals will have a male that will aggressively defend a group of specific females that are in essence their harem. Some other species will defend territories instead based on reproductive rookeries where females will move freely in and out of. When competition takes place, it is often violent, and almost always based on females or territory. Females are able to mate soon after giving birth due to their postpartum estrus. Often they need to come ashore upwards of twice a year for delayed embryo implantation to give birth and to mate. After delivery, the mother will suckle the young for a variable period of 4-50 days while otarids will lactate from 4-36 months. After lactation, females will migrate to feeding grounds for intensive foraging to recoup energy lost during lactation. They tend to be carnivorous eating shellfish, squid, penguins, fish, and crabs. Some will eat warm-blooded prey including other seals. They are often preyed upon by man, sharks, and orcas, and in arctic regions – polar bears.
Evolutional theorie suggests, based on molecular evidence, that pinnipeds evolved from a bear-like ancestor 23 million years ago during the late Oligocene or early Miocene epochs.
Folklore:
In various parts of the UK and Ireland, especially the Orkney Isles of Scotland, seals are identified with the faerie folk called the “selkie” which was a race of shape-shifting seals that can take human form. They would do this by removing their seal skin out of which a human would step out of and head ashore to blend with humans and mate with them.
- Harbor Seals: http://www.technogypsie.com/science/?p=264. “The only resident marine mammals at Yaquina Head are harbor seals – the most widespread seal in the North Pacific. Harbor seals are strictly carnivorous. They eat small bottom fish, rock fish, herring, squid, octopus, and many other fish. Large fish like salmon usually make up only a small portion of their diet. Most prey is eaten underwater but large fish are sometimes brought to the surface. Although seals can dive to depths of almost 600 feet (200 m), they need not test these limits in the relatively shallow, rich waters off Yaquina Head. Bottling and crawling – When storm waves and daily high tides wash over their haul-out areas, seals spend most of their time in the water. Look for them bottling with their bodies vertically submerged and only their face and nose peeking out. Bottling is a resting posture for seals. On land, harbor seals move by heaving their bodies forward caterpillar style. Here most seals haul out and rest on Seal Island at low tide, and re-enter the water to feed during the incoming tide. A single pup is born: Once a year, the female gives birth to a single pup, usually from April through June. Even though the pups can swim from birth, those born in rough water sometimes drown in spite of their mother’s efforst to help them. Seal pups are weaned at about 4-6 weeks but they may remain with mother for several months. ” ~ information sign at Yaquina Head National Park, Newport, Oregon. http://www.technogypsie.com/reviews/?p=25775
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Seal ( http://www.technogypsie.com/science/?p=264); Free Day at the Denver Zoo – ( http://www.technogypsie.com/reviews/?p=28145), Denver, Colorado. New Life in Colorado: Chronicle 26 – Chronicles of Sir Thomas Leaf and Prince Cian. Adventures in Colorado. Photos taken November 4, 2016. To read the adventures, visit http://www.technogypsie.com/chronicles/?p=21965. To read reviews, visit: www.technogypsie.com/reviews. All photos and articles (c) 2015/2016 Technogypsie.com – by Leaf McGowan and Thomas Baurley. All rights reserved. www.technogypsie.com/photography
