It surprises many people to learn killer whales are classified as dolphins. Like dolphins they are social, intelligent, and communicate with each other with surprising complexity. Most humans think of killer whales, popular name notwithstanding, as gentle and humorous. Families line up to see their amazing antics at the seaquariums.
Yet unlike their smaller cousins, they also have the capacity to terrify. A recent display of fury, fortunately directed at a great white shark, is breathtaking in its ferocity. (See video below: “Killer Whales Attack and Kill Great White Shark.”) Yet for all their predatory instincts, they are not known as human-killers, with extremely rare exceptions by orcas in captivity. There has been no recorded fatal attack on a human in the wild, and only six recorded non-fatal attacks, which normally turn out to be orca play activity. Yet they are avowed enemies of sharks—which in many cases should make them allies of humans and other potential shark bait (as in “the enemy of my enemy is my friend”).
“The great white shark is an apex predator of the seas and has no natural predators other than the orca,” according to Thomas Peschak, author of Currents of Contrast: Life in Southern Africa’s Two Oceans. 
Video: “Killer Whales Attack and Kill Great White Shark.”
Great White for Dinner?
This extraordinary footage is documentary video of a great white shark defending itself against a killer whale—and badly losing. For those who cowered in fear at the screening of Jaws, we might silently cheer the killer whale’s aggression. Or, we might watch the video in horror, watching as two monsters of the deep battle each other—the marine equivalent of Godzilla and Mothra.
“Killer whales and great white sharks,” the video narrator says. “Animals so dangerous, they wouldn’t dare challenge each other. Or so we thought.”
On the video you can hear a boy on the boat ask, “Is he eating the shark?”
“Off the coast of California,” the narrator continue, “it happens. The ultimate clash of the Titans—leaving biologists mystified.” In the film, they document a team of experts trying to “make sense of the carnage.”
Orcas “Hate” Great White Sharks
In fact, it’s not a big mystery. As comments on the video from viewers indicated, orcas go out of their way to fight sharks. “Killer whales HATE sharks. I’m from Washington State. Trust me, orcas nailing sharks is not uncommon,” wrote Daryl Buck on YouTube.
Dolphins and killer whales—family-related—appear to hate all sharks with a near-emotional zeal. Unlike most mammals and fish, they don’t fear great whites. There are many documented cases of dolphins rescuing humans from shark attacks. Is this a noble characteristic, a love of humans, or a natural instinct to fight their enemy the shark?
Orcas Differentiate Between Humans and Marine Mammals
Killer whale watching is a popular tourist pastime. In coastal waters, kayaks full of tourists row out to play with wild orca pods. How do orcas differentiate between Tilley hat–wearing spectators in kayaks, out to gawk at their playful antics, and seals, otters, birds and other gourmet treats?
“These intelligent whales have never injured a human in the wild,” explains an article on the Sea Quest Expeditions website. The company takes crowds of tourists out in kayaks—boats much smaller than the whales—to play with orcas.  “Only ill-treated captive orca whales have harmed people. Orca whales are extremely aware of their surroundings and NEVER collide with kayaks. They approach kayaks with the same respect that we offer them.”
Like man, orcas are at the top of the food chain, dominated by no other species. They have no apparent fear, even of great white sharks. Fearlessness, combined with human-like social behaviour, makes man and orca more alike than unalike. Like all dolphins, orcas are considered intelligent, emotional and social.
Intelligence Second Only to Man’s?
Many scientists claim dolphins and their relatives the orcas have intelligence second only to that of humans. This is based on a number of factors, including behaviour—for instance communications skills, mimicking skills and the ability to teach others of its species—and cognitive functionality, comprehension testing and physical brain size. 
Orcas Scarier Than Dolphins?
What makes the killer whale so much more apparently “scary” than their gentle cousins the dolphin? Popular “killer” name aside, our reaction to orcas is perhaps based on their sheer magnitude. Killer whales weigh in at six to ten tons, and can be as large as 32 feet—longer than most pleasure boats.  Compare that to the measly 12–13 feet and 1,500–2,430 pounds for a great white . Orcas are among the fastest marine mammals, clocking at 35 mph. Nothing commands respect more than rows of predatory teeth that would intimidate a grizzly bear. Yet all that aside, orcas are beloved of children at seaquariums, trusted for the most part by people who work the oceans, and considered more friend than foe.
Dolphins and Orcas: Man’s best friend?
“Forget the dog. Man’s best friend was a group of dolphins, when a man was attacked by a great white shark,” commented an NBC News host in a special report on a great white shark attack. Twenty-four-year-old Todd Endris was rescued by the miraculous intervention of dolphins—from a great white shark. “A monster great white came out of nowhere—had hit him three times . . .That’s when a pod of bottlenose dolphins intervened, forming a protective ring around Endris, allowing him to get to shore.” (Video below “Man’s New Best Friend”)
There have been several documented cases of humans being rescued from shark attacks by dolphins.  With orcas nearby, surfers need not fear great white attacks. Like their dolphin cousins, orcas do not tolerate their ancient enemy the shark. Which makes dolphins and orcas among man’s best friends.
Great White Shark: Enemy of Man?
Unlike killer whales, great white sharks frequently attack humans, and most attacks go undocumented. Many attacks result in fatalities, but the majority of victims survive. Scientists hypothesize that great white sharks, after a “test bite,” find humans to be undesirable prey, due to their bone density and propensity to fight back.  Great whites are also known to attack boats, although not as dramatically as depicted in the Stephen Spielberg thriller movie Jaws.
Man and orca, top of their respective food chains, social and intelligent creatures, appear to have much in common—including antagonism with the great white shark.
NBC News: “Man’s New Best Friend”
 Currents of Contrast: Life in Southern Africa’s Two Oceans, Thomas Peschak, ISBN-10:1770070869
 Killer Whale. Wikipedia
 Great white shark. Wikipedia http://en.wikipedia.org/wiki/White_shark
 “Dolphins Save Surfer from Becoming Shark’s Bait.” Today show