Nutrition
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Text Box: The Great White Shark, or Carcharodon carcharias is known as a macro-predator, or a predator that hunts prey that is smaller than itself. A Great White’s favorite prey to pursue are pinnipeds, or commonly known as seals and sea lions. This is their favorite prey item because it is a very satisfying meal for the energy put into catching it. They also will eat other organisms including fish, dolphin, rays, deceased whales, some marine reptiles, and even other sharks! It is often seen that the Great White tends to only injure sea turtles, (tear off an appendage) but not completely kill or consume them (Martins, 2008)! Lately, since shark diving and sight seeing has become more popular, the Great White gets to feed off fish heads and other pieces of bait put in the water by humans! It is really not a sufficient enough meal for them, but hey, they also do not have to expend much energy to hunt for it!

Photo by Carl Roessler
Text Box: One of the most interesting things about the Great White Shark’s nutrition, is how they acquire it. There are a couple different methods, or ‘attack styles’ that they use to take down their prey. One way that they attack is the “underwater approach” where the Great White swims just below the surface of the water until it is close to the prey, then it attacks by turning its head upward and leaving the water completely. Another attack method is the “surface charge”, where the shark attacks by rapidly approaching its prey with its body partly above the surface of the water. Its rarely seen, but occasionally the Great White will perform an attack called an “inverted approach” where it swims upside down towards the prey item. The last and most common attack method the Great White Shark shows, is when it attacks its prey in a vertical fashion (as seen in the image below). This is the attack method that is common in movies where something (or someone) is floating on the surface of the water, when all of a sudden a Great White Shark comes flying straight up from the depths of the ocean to capture it (see the YouTube video of this in the ‘Related Links’ section). This attack method is more affective than the others because it is not only harder for the prey item to see the Great White, but it makes viewing the intended prey item a lot easier. Also, if the prey item does end up seeing the Great White before the attack occurs, it is unlikely that the prey item will be able to escape the high speed attack of this expert predator (Martins, 2008). The Great White has been known to reach speeds up to 15 mph while using these attack methods (Ferrari, 1999)! After the Great White has finished the attack portion of its feeding style, it moves on to how it is going to kill, and consume it. The most common method the Great White practices is the “bite, spit, and wait” method. In most cases, the Great White will put a nice big bite into the prey item, spit it out, and then wait at a safe distance for it to be dead, or significantly weaker. This ensures the conservation of the Great White’s energy, and so it will not become injured in the process of feeding. The Great white will usually use this method when they are pursuing pinnipeds because they have sharp teeth that can injure the Great White (Bowling, 1999).

Photo by Linda Reese
Text Box: Although the Great White does not have a host, it serves as a host for a large number of other organisms. For one, it was reported that approximately 30 different species of protists used elasmobranchs as a host. Also, there were 20 species of annelids, 80 species of nematodes, and well over 800 cestode species parasitizing elasmobranchs. All of these different species have been found to reside in different parts of the Great White. They have been found to live in places such as the skin, eyes, olfactory bulbs (nasal region), inner-ear, spiracles (structure behind the eyes known to pump water through the gills while at a resting state), gills, digestive system, esophagus, stomach, spiral intestine, rectum, gallbladder, liver, heart, spleen, gonads, brain, body cavities, kidneys, and even in muscles (CRC Press, 2004). As you can see, parasites live virtually everywhere in the Great White! Text Box: Once a Great White has captured and ingested its prey, it is time to digest it, which is a very interesting aspect of the shark’s nutrition. The prey that was ingested goes into the sharks stomach, where it is digested and then drained into a special intestine called a spiral valve. The spiral valve is a very unique structure in a Great White, and all elasmobranch’s digestive systems. This valve is a tube in the digestive system, that inside, looks similar to a spiral staircase. The elasmobranchs have no need for a long, loopy intestine because the spiral valve greatly increases the surface area, which in turn increases the absorptive surface for the intestine to ingest nutrients. After everything has been absorbed in the spiral valve, the excess is released through the cloaca, which is a posterior opening that releases waste (Lineaweaver, 1970). Another important part of the Great White’s anatomy is their circulatory system. As humans do, Great Whites have a closed circulatory system, and are warm– bodied individuals. They are endothermic, which means they create their own heat within their body. Great Whites can raise their body temperature well over the temperature of the water to stay warm. Being able to raise their body heat by 18° Fahrenheit has some definite advantages. Great Whites improve their strength and speed of their muscle contractions, as well as keeping their brain warm to stay alert in cold water. Also, increased body temperature in the stomach and spiral valve increases the rate that a Great White will digest its food items. One downside to being endothermic is that the Great White needs more nutrient intake to maintain the internal heating system (Martin,2007) .

Photo by Linda Reese