You might picture a seal like the ones you see at water parks, but those performers are more likely to be sea lions. Sea lions are more agile on land than seals because of their enlarged fore flippers. This is because seals’ bodies are ideally suited to aquatic life.
The beautiful seal reportedly has been seen swimming upside-down. Why is this the case?
Why Do Seals Swim Upside Down?
Some researchers have speculated that seals’ tendency to swim upside down may help them locate food in deeper waters. This is called a “hunt swim” or “scanning.” Seals’ eyes are on the top of their heads. When they turn over, it’s easier to see what’s underneath them.
It may also be helping them to spot predators that may try and ambush them from the deep. According to Utah’s Hogle Zoo, sharks stay low in the water and come straight up at the seals. Additionally, orcas can get creative when hunting their prey, including seals. Swimming upside down may give seals an extra vantage point from below may give the seal an extra chance for survival.
What Seal Species Are Known To Swim Upside Down?
The instinct to swim upside down in seals may be ingrained in them, but these are the most commonly observed seal species known to swim upside down.
The family of “earless seals” or true seals includes harbor seals, and the first of the seals that swim upside down! From white or light gray with dark dots to dark brownish black with bright spots, harbor seals’ colour varies widely across their range.
Male harbor seals can reach a maximum size of 1.7 meters in length and as heavy as 113 kilograms. Females, on average, are shorter (1.3 meters) and lighter (100 kilograms) than their male counterparts.
Harbor seals, like all true seals, lack external ears and are unable to use their rear flippers for land travel. Instead, they “bounce” like caterpillars. While harbor seals are typically thought of as sedentary and non-migratory, research shows that they can migrate as far as 249 miles from their tagged location. They do this to molt, have babies, tend to their young, get some sun, and keep the neighborhood predators at bay.
Harbor seals are far more graceful swimmers. They have the ability to stay at sea over several days at a time, sleep undersea for up to 30 minutes at a stretch of time, and forage for food. Fish, crabs, cephalopods, and shellfish make up the bulk of the harbor seal’s diet, which it seeks out in shallow and benthic waters.
Although they have been spotted diving as deep as 1,500 feet (460 m), they prefer to hunt alone in shallower areas (480 m). Great white sharks, Greenland sharks, orcas, Steller sea lions, and walruses are among the predators of harbor seals. If they managed to avoid predation, harbor seals can live for up to 35 years.
Northern Fur Seals
The northern fur seal is a highly migratory animal known to travel up to 10,000 kilometers. Females and young leave the Pribilof Islands to travel to offshore waters along the coasts of Canada, California, and even as far west as Japan. Despite the great distance, the vast majority of these species make an annual migration to the Pribilof Islands in the Bering Sea, which are located off the coast of Alaska.
The walleye pollock and squid are the principal food sources for northern fur seals. Other fish species that make up their diet include sand lances, salmon, capelin, herring, mackerel, hake, and anchovy. The deepest dive ever documented for a northern fur seal was 230 meters. They are frequently preyed upon by Steller sea lions, orcas, foxes, sharks, and sharks.
The northern fur seal is another popular target for seal hunters. The North Pacific Fur Seal Convention was signed by the United States, Japan, Russia, and the United Kingdom in 1911 after the population had declined drastically owing to uncontrolled hunting in the late 19th and early 20th centuries.
Food supply for northern fur seals could be affected by commercial fishing for walleye pollock in the Bering Sea. Similarly, the northern fur seal is vulnerable to entanglement in fishing gear in Alaskan gillnet and trawl fisheries and the Japanese squid driftnet fishery.
Numerous fur seals, especially young males, have been found entangled in trawl nets, plastic packaging, and synthetic or natural twine during surveys in the Pribilof Islands.
Antartic Fur Seals
Antarctic fur seals are huge, robust, and captivating mammals that have adapted to the harsh environment of the Southern Ocean and the sub-Antarctic islands that border it. In this species, the gender disparity between males and females is the widest of any mammal.
Males are roughly five times heavier and longer than females. Females and young ones are typically gray with paler undersides, whereas adult males have dark brown coats. Puppies are born completely black but will molt to a silvery gray coloration between two and three months.
Unless breeding or molting, the Antarctic fur seal is solitary. Seals typically dive to depths of 30 meters for two minutes when foraging. Fish, krill, crustaceans, and cephalopods like squid and octopuses make up the bulk of the Antarctic fur seal’s diet. The main food source on the South Georgia Islands is the mackerel icefish. Some smaller penguins could be on the menu, too.
Humans nearly decimated the Antarctic fur seal in the 18th and 19th centuries due to severe hunting for its fur. Entanglement in human-made materials, including polypropylene straps, fishing nets, and nylon string, is the primary cause of mortality for these seals nowadays.
The Weddell seal is a massive mammal. Adult males and females measure roughly 3 meters in length and weigh between 400 and 500 kilograms. The head is rather small compared to the rest of the body, and the coloration is often mottled grey and black on the back with a mainly white underbelly.
Most of a Weddell seal’s life is submerged in the Antarctic ocean. The Antarctic fur seal can be found in the farthest south of any seal species. Seals of this species rarely travel more than a few kilometers from their birthplace.
By diving beneath the ice, these seals may avoid their major predators, orcas and leopard seals. The natural conditions benefit their fishing efforts as well. When hunting beneath the ice, they can dive under their prey. The fish above the seal is illuminated by the ice above and can be seen in silhouette as the seal rises.
The Weddell seal can also use air to find prey. They may use compressed air to force open crevasses in the ice. The seal uses this strategy to flush off smaller fish, which it subsequently devours. Although cod and silverfish are two of their favorite foods, harbor seals consume small crabs, octopuses, and other marine organisms.
Weddell seals have been recorded diving as deep as 2,000 ft for as long as 45 minutes. But like other marine creatures, they must come up for air at some point. Weddell seals utilize their teeth to create and maintain air vents in the ice pack when no natural openings are present.
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