Cue the Jaws theme song. We are about to dive into the exceptional biological features of the great white shark (Carcharodon carcharias) that combine to form this incredible predator of the ocean. We highlight the work of shark specialist Dr. Geremy Cliff and sensory biologist Dr. Craig O’Connell in the Smithsonian documentary, Great White Code Red, as they unveil the mystery behind the great white’s success as a killing machine.
It is unusual to think of a shark’s hearing sense because they lack apparent ears. This is partially correct; while great whites and other sharks don’t have external ears, they possess much sharper ones underneath the top of their heads, with only two tiny pores to show for it. These inner ears are lined with thousands of minute cilia, hair-like structures that do a little wafting dance even if the slightest amount of sound waves pass by. Sounds can be picked up from large distances and at very low frequencies, such as the gentle splash of a fatty seal. As a result of this sound, the cilia’s wafting motion shoots a signal to the brain and the shark begins to think about its next meal.
Sensing Prey’s Movements
Now that the shark is keyed into the sound of a seal, dolphin, or other hearty food, it moves close enough to detect something else altogether, movement. Every flap of a seal’s flippers, every twist and turn the seal performs displaces the surrounding water. It’s like throwing a pebble into the lake and watching ripples echo away from it. These ripples can be felt by one of the great white’s coolest features, the lateral line (Boord & Campbell 1977). The lateral line is a long strip of sensory tissue found on either side of the shark from head to tailfin. Once again, this is made up of cilia that dance when hit with vibrations and sends a warning signal to the brain. It essentially allows the shark to sense its prey’s movements from all angles which gives the shark more intel about which seal to choose from the pack.
It doesn’t take a top-class predator to sniff out the stinky odor of seals. But great whites take it a step further than simply smelling them. Each seal generates it’s own signature oily scent, and this uniqueness helps the shark narrow down the unfortunate animal to feast on. Great whites have two nostrils much like us, but use both of them separately – unlike us. Moving its head in a menacing left-right notion, it senses the waters with each nostril before deciding which side feels the strongest and makes its way there. Along the way, it filters this smell through “screens” in the nose which breaks down the individual components of the seal of interest. The specific prey of choice is then locked in the shark’s mind.
Finally, the shark is close enough to utilize its exciting superpower: electroreception. Great whites, as well as some other sharks and rays, have the incredible ability to detect electric fields around them. They do this through biological weapons called the Ampullae of Lorenzini (Murray 1962). Fancy. These are small pore structures that dress the shark’s snout and possess a super sensitive gel-like substance. This gel can sense electric pulses generated from every muscle movement that occurs in prey, including their heartbeats. At this point, the shark has a complete profile of its meal and moves forward to catch a long-awaited glimpse of it.
One of the great white’s most important features is its eyesight; the dark waters where seals and other prey are found calls for highly efficient vision. Shark’s have super cool eyes with what the Smithsonian documentary states as “built-in sunglasses + night-vision.” This combination is scientifically known as the tapetum lucidum, a layer of reflective tissue that lines the back of the eyes. This phenomenon is also seen in cats, dogs, cows, and a number of other animals. In bright light, it dons sunglasses mode and shields the eye. In dim conditions, it reveals a reflective surface like a mirror that bounces light back and doubles the amount of light that entered the eye.
Now that the shark has heard, sensed movements of, smelled, sensed electric fields of, and caught sight of its prey, it can move in for the grand finale attack. With sheer strength and a motor pump of a tailfin, the great white propels upward and snatches the clueless animal with its razor-sharp triangular teeth. A well-earned meal for sure.
So what do you think is the most fascinating aspect of the great white shark’s hunting regimen? What are other incredible features that deadly predators possess? Let us know your thoughts in the comments below!
Boord, R. L., & Campbell, C. B. G. (1977). Structural and functional organization of the lateral line system of sharks. American Zoologist, 17(2), 431-441.
Cliff, G., & O’Connell, C. (2014). Great White Code Red. Smithsonian Channel.
Murray, R. W. (1962). The response of the ampullae of Lorenzini of elasmobranchs to electrical stimulation. Journal of Experimental Biology, 39(1), 119-128.