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Sunday, July 8, 2012

Myths In The Open Water: Sharks vs. Dolphins

There is a certain amount of misinformation reported in the media about open water swimming. Open Water Source looked at the data in an attempt to distill fact from fiction, reality from rumor.

One issue that is commonly reported in the press is that "Dolphins protect swimmers from sharks."

This oft-used quote is a dramatic indication how scary it is to swim with sharks and how comforting it is to swim with dolphins.

But is it true?

Are open water swimmers truly and naturally protected from sharks by dolphins and porpoises as is commonly believed by many channel swimmers? There are a wide variety of opinions on this topic.

Many open water swimmers around the world, especially channel swimmers and marathon swimmers, often tell newcomers that when dolphins or porpoise are near them in the open water, there is no need to fear sharks. It is often said to be a sign of good luck and protection. The belief is that sharks fear dolphins and porpoises that can easily defend themselves against the apex predators - and will, in turn, protect swimmers, their mammalian friends.

Escort pilots of channel swimmers throughout the Pacific, from the Catalina Channel to the Hawaiian Islands, also share this opinion.

According to Peter Klimley and David Ainley who wrote a book Great White Sharks: The Biology of Carcharodon carcharias, Great white sharks attack dolphins and porpoises from above, behind or below to avoid being detected by the friendly mammal's echolocation. The targeted species include dusky dolphins, Risso's dolphins, bottlenose dolphins, Humpback dolphins, harbour porpoises, and Dall's porpoises.

Scientists like Michael Heithaus also raise possibilities that differ from the widely held beliefs of open water swimmers. He presented a study called Predator–prey and competitive interactions between sharks (order Selachii) and dolphins (suborder Odontoceti): a review, that shares findings similar to television programs like the Discovery Channel's Are Sharks Afraid of Dolphins?. He concluded that sharks remain the apex predator in the ocean and do not fear dolphins or porpoises, except perhaps when out-numbered.

His study in the Journal of Zoology (Cambridge University Press) stated, "White, tiger, bull and sevengill sharks are probably the major predators on nearshore cetaceans, but dusky sharks may also represent a risk. The risk that nearshore cetaceans face from sharks will vary with location. For example, the risk of shark predation is probably higher in tropical waters than in higher latitudes because of the diversity and abundance of large, predatory sharks in warm waters."

Richard Theiss of RTSea Productions believes what the scientific community has presented in published peer-review articles, but he also points out an important truth. "...what Michael had to say in his study is important: different species, different locations, different circumstances – all this makes it difficult to make a definitive statement. [In reference to the] Mythbusters video, there are errors in not making the distinction between a white shark’s role as an ambushing predator and that of a scavenger. Each generates different behavior patterns. As a scavenger, which is what it was doing with the floating tuna head, it can be easily put off by another large fish in the area (did it look like a dolphin or another shark?). It’s just looking for an easy meal and doesn’t want to have to compete for it. I’ve seen this many times with white sharks at Isla Guadalupe (see RTSea Productions video below).

So, sharks will kill dolphins on occasion – seeking a slow, sick, or aged fish, just like the Great white shark does in selecting a pinniped (seal or sea lion). What needs to be examined in a definitive study and not just through anecdotal storytelling is whether dolphins will show any aggressive tendencies towards sharks. It’s not so much as to whether sharks are scared of dolphins, but whether dolphins are fearless when it comes to sharks

Heithaus, who directs the Shark Bay Ecosystem Research Project in Shark Bay, Western Australia, encourages further study of the natural relationship between sharks and dolphins where more information and understanding about the nature of shark-dolphin interactions is needed.

A MythBusters episode on the Discovery Channel also explored this issue: Are Sharks Afraid of Dolphins?.

Other commonly held beliefs among open water swimmers include:

1. Most body heat escapes through your head in the water (read here).
2. Commercial jellyfish ointments will prevent jellyfish barbs from firing into the skin of open water swimmers.
3. Black wetsuits lead to shark attacks (read here).
4. Shark risks increase at dawn and dusk (read here).
5. More people have been in space than have swum across the English Channel (read here).

Copyright © 2012 by World Open Water Swimming Association


  1. It is known fact that as fast a dolphins and porpoises swim, a shark can swim more than twice as fast. So dolphins cannot outrun a shark if a shark attacks -- it would be like a human trying to outrun an attacking bear. It is also a known fact that dolphins and porpoises are social animals and are rarely found swimming alone. When dolphins hunt they follow techniques that depend on cooperation and highly coordinated efforts. On the other hand, sharks are not a social animal -- they are strictly loners who hunt alone. Sharks would never work cooperatively to attack a dolphin, but dolphins would work as a team in attacking a shark if threatened by a shark. And there is more than one instance where dolphins have killed sharks by battering them. It is not clear whether sharks fear dolphins or dolphins fear sharks (though it is more likely that the dolphins have fear because fear usually is a sign of intelligence and dolphins are far more intelligent that sharks), but one thing is sure -- you rarely see them together. Where you see sharks in numbers you do not see dolphins or porpoises and vice versa. So you can feel safer as a swimmer if you are in a region where dophins or porpoises are prevalent. Sharks are dim witted but very efficient hunters and killers and even without fear they may have instincts that tell them that dolphins or porpoises in groups are BAD news and something to avoid.

    1. Actually you are incorrect on a few statements. It has actually been shown that sharks do often coordinate attacks and are more social than we previously realized. Sharks also are far from dim witted, and while they are no where near as intelligent as dolphins they do posses a degree of intelligence.

    2. I assume you mean "an average human outrunning an attacking average bear." Otherwise, I call on Usain Bolt and a Koala bear (if we're being taxonomically correct, then a sloth bear). Human probably wins in that case. I can imagine an "average human," but an "average attacking bear" depends on the species.

    3. I assume you mean "an average human outrunning an attacking average bear." Otherwise, I call on Usain Bolt and a Koala bear (if we're being taxonomically correct, then a sloth bear). Human probably wins in that case. I can imagine an "average human," but an "average attacking bear" depends on the species.

  2. You also failed to mention sharks are not as energy efficient as dolphins... like s cheetahs are faster then humans but on average they cannot outrun us.. simply their energy dies out faster so their better at surprise attacks but not stalking prey till exhaustion like humans whales and dolphins do. A shark could.Not catch a dolphin in a long race but could if he caught the dolphin off guard and got him asap . . But this is again not so smart a idea as dolphins would begin ramming into the sharks ribs bursting them and useing sonar to confuse its senses... a shark must keep moving or it will die and being under constant assault from dolphins is almost a sure death either from them or from suffocation. Dolphins are no joke to sharks the same way we are no joke to many other animals... but sharks are not dim either..their smart enough to know a dolphins happy go lucky attitude dies not mean it won't kill him dame many other animals learn of humans.. Dolphins and humans have allot in common the use of intelligence, numbers and social skills to cripple foes.

  3. Well, from my experiences, sharks and dolphins like to munch on the same fish.....so when I dive, if I see dolphins, I become more weary....all in all, I would never take trust that dolphins in the water means no sharks...
    -Big Tom

  4. I don't claim to know much about either species, but I do know that a dolphin can easily kill a shark. All it has to do is ram the shark by the left gill, because that is where the shark's heart is. Ramming it there will stop the shark's heart, thus killing the shark. I learned this from an ex-navy seal friend of mine. They were taught that if they encountered a shark, while on a mission, they should get on the left side of the shark, reach inside the left gill where they will find the shark's heart then grab it and pull. this the easiest way to kill a shark.

    1. Whoa, slow down there Rambo, this isn't the movies..
      LMAO, navy seal or not I'd love to see this actually happen.
      You are correct that a dolphin can kill a shark relatively easy. I have seen this first hand but it was a group (pod) of dolphins and they made very short work of that shark. (And yes, it was a decent sized Zambezi).

    2. Whoa, slow down there rambo. Navy seal or not, this is simply not going to happen in real life.

      You are correct the a dolphin can take out a shark. I have seen this is real life but it was a small pod of dolphins that took a decent sized Zambezi shark. They seemed to somehow confuse it, as well as darting all over the place, the shark could handle the distractions and then would get rammed every now and again. They made very short work of that shark, no longer than 3-5 minutes.
      As to the other replies, the shark tried several times to flee, the dolphins were just as fast, if not faster, so I would say that a shark (at least that one) was very well aware that it was in serious trouble.

    3. Im thinking that when the reach in gill heart grab kill manover fails im sure you still may be able to poke it in the eye with your stump.

  5. Dolphins are no match to sharks. Sharks can kill and even exterminate dolphins. Dolphins are so weak thus they are helpless from shark attack. Whales and orcas can be safe from sharks. I meant dolphins from sea world or flipper. Very feeble creatures compare to sharks

    1. you don't seem very bright

    2. Those are called orcas.. n they can eat a shark. Dolphins outclass sharks in all aspects.. their fins allow them to maneuver up n down, left n right.. while a shark can't.. brains over Braun.. they will come from below the shark n hit them with their snout.. which is very hard bone.. n do internal damage if not knock the shark out cold.. sharks don't fear dolphin's.. dolphins are Fearless towards sharks.

  6. Sharks can kill and eat dolphins so easily. Dolphins are too weak and helpless from shark attack. Sharks have 99% chance of eating dolphins. Orcas on the other hand kill sharks but dolphins are very weak creatures

  7. Sharks do eat dolphins. In fact sharks love seals and dolphins most. Dolphins are helpless from shark attack. Dolphins are much slower and weaker than sharks. Sharks are very strong and dolphins are very weak. Not orca I meant dolphins

    1. This is completely a opinion. Dolphins are definitely a threat to sharks, they are not helpless like you think, I have seem a small pod kill a shark and I have also seen sharks flee when a pod wards them off. I would also say that dolphins are not slower than sharks, the opposite is actually true.

  8. Just for interest sake...

  9. you guys just don't get it, obviously a shark if much larger than a dolphin will attempt to hunt the dolphin, however, what you guys are missing is, if the shark and dolphin are of the same size then the dolphin is faster and can defend itself against the shark, it's all about size.

    1. Cooridinated numbers. Lions are much bigger and stronger than humans but know to fear a group humans. Dolphins are nearly always in groups.

  10. Orcas are a type of dolphin and they can kill a shark 1 on 1 against a species of smaller dolphin I would say a shark like the great white would win

  11. Dolphins are sharks favorite prey. Dolphins cannot fight. In fact a single great white or tiger shark can rout ten adult dolphins!!!

  12. There was a footage that one single tiger shark showed up and hundreds of dolphins fled!!!

  13. Dolphins are no match to sharks!!!

  14. Sharks are predators of dolphins!!! Dolphins are lovely but week and can't fight!!! Sharks faster and tougher than dolphins!!! In fact sharks love to eat dolphins and seals most!!!


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