Seals ‘porpoising’ – leaping in and out of the water like dolphins
Suddenly the seal was no longer swimming, but instead found itself lifted up into the air between two powerful jaws. The attack from the deep was so sudden that the sea mammal didn’t even have time to consider escape. There would be no sunbathing for the seal that day, and no fishing tomorrow, as the Great White shark swam away with its prey.
A shark launches itself from the water, probably moving its head violently from side to side to kill or disable the prey in its mouth.
Seal Island is, in essence, a hunk of granite protruding six meters above the waves. It is 800 meters (2,620 feet) long and 50 meters (160 feet) wide. This relatively small landmass is, however, home to about 75,000 Cape Fur seals. Once aggressively hunted by men, the seals of Seal Island are mostly left alone these days – except, that is, by their biggest predator in this area, the Great White shark. These sharks swim around the island, forming the previously mentioned ‘ring of death’.
Seals swim underwater to better see and evade sharks.
Even without Steven Spielberg’s terrifying (and often inaccurate) portrayal of their kind, Great White sharks would probably still be among nature’s most feared predators – and surely the most frightening fish in the sea! Fortunately for us, humans are not the prey of choice for these deadly giants of the deep. Great white shark attacks on people are normally just curious ‘sample bites’ rather than concerted attempts to turn us into dinner. Pity the poor seals, though; they’re one of the Great White’s favorite foods.
A shark bursts up from the sea in spectacular fashion.
In order to find their prey, sharks have two specialized sensing mechanisms. One is their sense of smell, which, although impressive, has been overrated in the past. It was recently proven that sharks cannot, in fact, smell a drop of blood in an Olympic-sized pool, as some people have been led to believe. But they can certainly sniff out a nearby seal.
Another sense used by the shark is its ability to pick up electrical fields emitted by anything swimming in the sea. This incredible faculty is sensitive enough to distinguish between different types of breathing patterns, and even when an animal is bleeding. Very important for a hungry predator looking for an easy meal!
This seal may have escaped a shark but, sadly, it looks like it was too late.
Sharks are ‘apex’ predators; that is, they are at the top of the food chain. They are ruthlessly efficient hunters that use several methods to capture and kill their prey. The most spectacular technique is that described at the beginning of this article, where the shark rises from the deep in a vertical line to snatch its unwary victim (normally a young seal that is less experienced in evasive maneuver) from below.
A shark makes a vertical lunge out of the water, known as a ‘Polaris Attack’.
In the ‘Polaris Attack’ (as this underwater ambush is known), the shark speeds up to the surface, often emerging partly or even completely from the water. Sharks can launch themselves to 3 meters (nearly 10 feet) above the waves, as was demonstrated in one incident in which a Great White at Seal Island surged up out of the ocean and landed on a research boat – which must have been a bit of a shock for the crew! After a couple of false starts, it was returned safely to the sea, apparently no worse for its adventure.
Even when the shark doesn’t get the seal in its mouth, the breaching predator can still do damage.
Watching these large predators breach the water is a magnificent sight, and one that draws many visitors to Seal Island in the hopes of seeing it happen. For the seal that is the target of this attack, on the other hand, it is normally fatal.
If they are not killed straight off, then the unlucky prey is generally in no condition to swim away. A seal caught in the shark’s vicious grip is likely to be shaken violently from side to side, causing death or at least incapacitation through neck trauma.
Seal Island: It’s easy to see how it got its name.
Yet seals are not without strategies of their own. For one thing, they know to travel in groups rather than alone. On Seal Island, for instance, the animals leave their rocky shore in groups of eight to twelve. That way, if a shark attacks them, they can scatter in several different directions, confusing the carnivorous fish long enough for them to get away.
If the seal is unlucky enough to be caught alone, it will try and elude its pursuer by zigzagging away, in a maneuver known as ‘working the shark’. This trick doesn’t always succeed, however, as the shark may suddenly snap its head sideways to catch the furry animal.
A Great White shark spots something it wants and displays its impressive teeth.
Another way the seals avoid becoming shark food is by swimming underwater when they are within 50 meters of the island. Presumably this makes it harder for a shark to sneak up on them or use the deadly ‘Polaris Attack’.
When they’re not actually swimming beneath the waves, the seals keep an eye out for approaching sharks by floating with their heads down in the water. After all, they know exactly from which area the enemy is most likely to strike!
A colony of African Penguins also shares the island.
Seal Island is an important nature reserve, albeit one without trees or any other plant life. Its wealth is truly in its wildlife. As well as the Cape Fur seals, around twenty-five species of birds (including African penguins) live on this barren island.
Sunset over Seal Island
Both Cape Fur seals and Great White sharks are species that have been heavily hunted in the past; the seals for their fur and the Great Whites for their fins, jaws, or simply as trophies.
Although the seals of Seal Island are protected today, in Namibia they are still being culled in their thousands, and Great White Sharks are on the International Union for Conservation of Nature (IUCN) ‘Vulnerable Species’ list. All of which merely adds to the ecological importance of this small – yet amazing – rock in the sea near Cape Town.