Article Summary #1 – The Gray Reef Shark
In a place called the Bikini Lagoon in the Marshall Islands, there lives a great, wild predator – the gray reef shark. Over fifty years ago, shortly after World War II, atomic bomb tests were conducted at this site. At first glance the beach looks like a tropical paradise, but in truth the water and the land share a poisoned history from the era when 23 atomic tests were conducted here. Soon after the first atomic clouds mushroomed into the sky over Bikini Lagoon, scientists went out to test the waters as they say. What they found was that the ocean life was riddled with high doses of radiation. Given these sinister findings, one might think that since then the radioactivity would have ruled out much of the wild life, but this is not the case. You see, the marine systems, once bombarded by radiation, have been flushed by time and the tides to regenerate reefs swirling with life. With all that in mind I pose the question – "How have these gray reef sharks adapted their bodies and their communication skills in the wake of this radiation?" In the following information from the article, I hope to answer this.
The main predator of these waters is the above mentioned gray reef shark, which happens to be the most populous shark in these waters. It belongs to the large family of requiem sharks – the Carcharhinidae, which are known to be sleek, swift creatures found throughout tropical seas. The range of the gray reef shark (Carcharhinidae amblyrhynchos) extends all the way from the Indian Ocean eastward to Hawaii and the islands of French Polynesia. Along the way the gray reef shark establishes its’ home along the coral reefs. It is documented to be a medium sized shark, growing to six feet or more. It also happens to be one of the most aggressive sharks in the waters of the world.
However, what truly sets this great shark apart from the others is the incredible body language it speaks. It can sense when its’ space feels threatened, and when it does it drops it pectoral fins straight down, raises its snout, and arches its back like a cat about to pounce, then starts swimming with an exaggerated weaving and rolling motion. This startling display serves as a warning sign of attack to all those around.
When feeding these great sharks it has been noted that they go crazy when dead fish are thrown from a boat. These feeding frenzies have been likened to mob behavior in humans, with the overload of stimulation taking away all inhibition. When feeding them live fish, to a hungry shark this is as effective as a dinner bell going off. All sharks have the innate ability to operate like high-powered antennas. They can hear over long distances the low-frequency vibrations emitted by a struggling fish; it too has been noted that they are likely to hear over as much as a mile. As the fish struggles these sharks noses can pick up the faint smell of blood spread over the ocean currents. Through visible pores on their heads that lead to special receptors, they detect at close range, electrical fields given off by animals, including humans. Although gray reef sharks will hunt alone, they often attack and feed in large groups, and to the swiftest goes the meal. However, in the midst of this feeding frenzy, the sharks show no aggression towards each other, despite the ferocity of their assault.
In this article I found a section describing a survivor’s tale of an attack by a gray reef shark, which I found very interesting and will summarize some of that story for you. We all know that getting attacked by a wild animal is probably the most basic human fear. The man described it as being hit by a "sledgehammer", that it was such a shock. He said that the shark seemed to come at him like a rocket, having only enough time to lift his hand just as the shark ripped through it with its teeth. Shortly thereafter he was rescued by a friend, and had said that the shark, "was not trying to eat me, it was in fact driving me away, quite possibly seeing me as a potential predator."
This article also brought up the fact that it can be a shark-eat-shark world. It has been captured on film that while a gray reef shark lies on the bottom of the sea floor, in a flash half of it is gone, devoured in a single bite by a 13 foot long tiger shark. But if in fact gray reef sharks only grow up to around six feet, we see clearly how natural selection works its wonders. Obviously something that is 13 feet in length has no problem eating a smaller shark – however closely related. If you’re hungry then you’re hungry, it’s called survival of the fittest.
The thing that astonishes me the most, however, is the fact that this wonderful lagoon where the great sharks live, truly healed itself. After man had violated this beautiful home of underwater creatures, time and mother nature has managed to triumph; once again giving a home to some of the most fascinating, stealthy creatures – the gray reef shark.
SOURCE: The National Geographic, January 1995. Close Encounters with
the Gray Reef Shark, by Bill Curtsinger. Pp.44-67.