Study shows dolphins don't deter sharks in the surf

Anthony Pancia
Swellnet Dispatch

Warning: This story contains images that some people may find distressing.

The theory that dolphins keep surfers safe from sharks has been blown out of the water with a Western Australian study.

Researchers from WA's Murdoch University Cetacean Research Unit monitored dolphin populations off the coast of Bunbury in the state's south west and Shark Bay in the north, and found shark bites increased each year from 2009 to 2013 — in line with rising ocean temperatures.

Dolphins in sheltered waters were "significantly" more likely to be bitten than populations in deep coastal waters. The research also saw a spike in attacks over the summer months of 2012–13.

Researcher Kate Sprogis said great whites and tiger sharks were believed to be largely responsible for the attacks in Western Australia.

"In the case of great whites, for example, once they get beyond a length of about 2.7 metres, they need marine mammals in their diet, so they will shift from fish to predating on seals, sea lions and they will also try for dolphins," Dr Sprogis said.

A dolphin bearing a substantial bite mark, thought to be from either a tiger or great white shark (Kate Sprogis/Murdoch University)

"We attempted to identify each bite mark, but often they get quite messy as the shark will come in from a side angle. We were able to identify a few that were from tiger sharks if the bite mark was broad, blunt or square."

Dr Sprogis said the research also concluded there was little difference when it came to the sex or age of dolphins but lethal bite marks tended to come from "large predatory sharks".

"In the two areas the research was carried out, there was a 74 per cent bite rate off Shark Bay while in Bunbury it was 17 per cent," she said. "But that is just the dolphins we do see; many more would have sunk to the bottom so we could not include those that had incurred lethal bites."

Research indicates shark predation on dolphins is on the rise (Kate Sprogis/Murdoch University)

Dr Sprogis said the research team had initially hypothesised the incidence of sharks attacking dolphins were unlikely to increase over the years, but between 2007 and 2013 predation increased as ocean temperatures also rose in line with the La Niña weather pattern.

"The Leeuwin current [a warm ocean current found off the west coast of Australia] was bringing the warmer waters down with it," Dr Sprogis said. "What we did see was an increase in shark bites on the dolphins. We also think that drew more tiger sharks into the areas with the warmer waters."

Dr Sprogis said there was no available research to indicate dolphins in turn predated on sharks but there was evidence they did "try to escape".

"They will leap out of the water and alert other dolphins of the presence of sharks," Dr Sprogis said. "But if the water is shallow, they often can't turn quickly enough or they don't acoustically hear or detect sharks in proximity, so it might be harder for them to react and that would be a large reason in why they get bitten."

Dr Sprogis, also a keen surfer, said the research put paid to a long-held theory for surfers relying on the presence of dolphins to deter sharks.

"Growing up, I also thought that every time I saw a dolphin out in the surf everything was fine," she said. "Seeing these shark bites on dolphins though, I now know sharks do predate on dolphins and you shouldn't rely on that theory when you're out in the surf."

© Australian Broadcasting Corporation. All rights reserved.

(Homepage photo of Pete Tomlinson by Shane Smith / Salt Eyre)


crg's picture
crg's picture
crg commented Wednesday, 12 Sep 2018 at 9:58am

I've a mate who in the last year has taken to flying drones and filming. You should see the footage when he takes high shots of dolphin pods. 9/10 times trailed by sharks.

Craig's picture
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Craig commented Wednesday, 12 Sep 2018 at 1:53pm


gcart's picture
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gcart commented Wednesday, 12 Sep 2018 at 10:23am

A different way of viewing this is to observe the behaviour of the pod of dolphins that is near you .I always wonder whether they are coming in to a group of surfers and using them as shields , that is moving to the other side of the surfers from the predator. You'd have to assume that when they appear to be happily flapping around , jumping out of the water and surfing the waves with you , that they're just enjoying themselves - or are they ? When the pod seems to be moving at great speed , business like : surely there is something tailing them. That's the sort of advice I should be able to expect from the "more research" that "needs to be done" .

Terminal's picture
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Terminal commented Wednesday, 12 Sep 2018 at 10:39am

Unreal hypothesis gcart! I wonder, though, if dolphins are cognitively equipped to do this (i.e., think for the shark that it will select the human over themselves). I'm pretty sure I've read in the literature (peer-reviewed, published for Crypto) that mirror self-recognition (MSR) has been documented in at least one species of dolphin, so maybe. MSR is a big deal, as only really occurs in the cognitively higher-order species (primates etc).

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JJGav commented Wednesday, 12 Sep 2018 at 10:57am

Flipper has a lot to answer for on this... You just have to look at the great David Attenborough documentaries with sharks, dolphins, whales, sea birds all feeding together on sardines in South Africa... Sure, they are different species to ours here in AU however the concept that sharks are not present or even more ridiculously "repelled" by the presence of dolphins is completely illogical. Perhaps an analogy is that you're safe on the savannah whilst there are zebra around?


Blowin's picture
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Blowin commented Wednesday, 12 Sep 2018 at 11:18am

“ Revelations “ such as this make me lose respect for the scientific community ie the prolonged realisation of a fact long known to non academics dramatically undermines their credibility.

Terminal's picture
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Terminal commented Wednesday, 12 Sep 2018 at 11:41am

The heading is misleading as this is not what the research paper is about. They were quantifying predation attempts by sharks and whether this differed between dolphin ages, sex etc. If you care to read the introduction of the peer-reviewed paper you'll see that they provide extensive evidence reported elsewhere over decades of shark-dolphin predation.

blindboy's picture
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blindboy commented Wednesday, 12 Sep 2018 at 11:32am

Science quantifies and records Blowin. " Facts long known to non-academics" are anecdotal evidence and are commonly used as a starting point for research. Unfortunately those "facts" often turn out to be wrong as in the commonly held view disproved by the research. It may be, as you assert, that this was already known to some non-academic groups but I can't see how that undermines the credibility of the science.

Blowin's picture
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Blowin commented Wednesday, 12 Sep 2018 at 11:37am

Dolphins have been studied by science for hundreds of years and they have only just confirmed a fundamental fact about dolphins that is extremely easy to assess.

Stay tuned....results from scientific community due by 2025 to confirm if dolphins eat fish regularly.

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CryptoKnight commented Wednesday, 12 Sep 2018 at 1:21pm

I like dolphins around because you can gauge from their behavior if something is trying to eat them or not. Same with seals. Even salmon, and other big fish that you see in the reef.

One morning I was surfing an out of the way beachy with the twinnie ledge, and the twinnie ledge junior, who loves filming dolphins, when we spotted action way out at sea. Eventually we could see that it was a pod of a smaller type of dolphin, porpoising at high speed. First we thought it was cool, then we realised they were running for their lives, and veering more and more directly towards us. We had all been involved in cases of seals and dolphins using us as decoys, when being hunted, and the way that they were acting, we figured that was their plan. So we bolted to the beach.

simba's picture
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simba commented Wednesday, 12 Sep 2018 at 1:52pm

Wasn't that long ago it was a pleasure to have a pod of dolphins hang around while surfing,encouraging them to come in closer and many times ive turned around to have one sitting within 2 meters just laying there checking me out .But its a bit different these last few years with the increase in white numbers over here because its fairly obvious that, as it says in the story above that they need more food as they get bigger way more muscle to feed.So i become a lot more wary now when a pod approaches .


JosephStalin's picture
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JosephStalin commented Wednesday, 12 Sep 2018 at 2:03pm

Seen how they interact when i was working on prawn trawlers, dolphins are very smart

Standito's picture
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Standito commented Thursday, 13 Sep 2018 at 7:14am

Years ago my best mate and I were surfing the Beacon Bombie off 13th beach
We had a big pod of dolphins coming closer and closer... Well, in between the dolphins was a white pointer about 12ft long and wider than a 44 gallon drum.
They were all just cruising together. Certainly changed my thinking...
Needless to say we go the hell out of there !
The 300mtr + paddle back to shore was bloody scary!

Craig's picture
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Craig commented Thursday, 13 Sep 2018 at 7:26am


truebluebasher's picture
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truebluebasher commented Thursday, 13 Sep 2018 at 6:35pm

As with Man on Land, Dolphins are judge, jury and executioners of Ocean Kingdom.
Dolphins are also the most efficient killers in the ocean.
Dolphins kill Sharks/Porpoise & Humans even their own offspring if any threaten their pod.

Dolphins hunt & kill shark for food they're even branded killer Whales (Orcas are dolphins)
Dolphins do mate with Killer Whales! see: (Wholphin). Taste for flake is in the blood bro!

Warm blooded Dolphins have horizontal flutes enabling dual realm (3d) fight-scapes.
Dolphin sonar can hone in on Shark's vital organs & receptors to land a killer blow.
Speed from beneath to ram Shark or smash Shark's head from air bomb raids.
Fin blow slapping in concert with bubble curtains to fowl gill breathing.

After entering a Dolphin pod the first time... Sharks are once dumbstruck twice shy.
Never will they return to hunt a Pod (Two is too many) Slower Dolphins can be picked off.

In a sense a Pod will deter mature Sharks but a lone Dolphin will equally attract a Shark/s.

Tables are turned when Sharks round up loner(young/elderly) Dolphins into shallows.
Sharks vertical flute has more horizontal hunting thrust to cloak a Dolphin.
Shallows are also home to kelp beds that isolates Dolphin's echolocation to pod.
Eliminating any exits for Dolphin they simply bank off a reef /shoal or shoreline as a pen.
Dolphin's defences or counterattack is severely limited & injury to Shark is minimized.
Note the bites are said to be from above or on Dolphin's sides rather than from beneath.

Why do dolphins kill their own defenseless calf or Porpoises & Humans?

Dolphin gestation of 12 months + 3 year calving really pisses off Male Dolphins.
Mother Dolphins basically love being motherly resisting frisky males for(4 years)
She can even fool then shut out the males...Plays really hard to get.
To get close to sexy Mama male Dolphins need a Plan B.

Plan B comes in the twisted form of infanticide... being a female Dolphin aphrodisiac..
When a calf dies mamma becomes red hot mamma.
With female Dolphin being so inviting and male "Porpoise" as chief harbour humper.
Female Bottlenose Dolphin + Randy male Porpoise a perfect match at office pool party?

Dolphins put the kid in day/nightcare & Cuz Porpoise has a crack...Brat Cuz is dead meat!
100's of Porpoise/calves are found pulverized disemboweled & spat on...Not a pretty sight!
note: Killing theory changes daily thick and fast more than days in the Thursday's!

(Porpoise/calf Demolition Derby) kills an hour at Psycho Dolphin's bucks party.
Dolphin Godfather hierarchy determines which gang-bangerz get to smack the bitch up
Female Dolphin takes on all comers but only turns on her beau!...Sea Siren if ever!

As with dolphins attacking humans...a rare breed of humans say it's rare...
Usually payback is reason given but what that means as in dolphin sense.
Any dolphin knows that by tugging on a human's leg they can/do drown us rag doll style.
They could bite our legs or nibble our toes just as easily but prefer the playfully slow death.

Brazil's free Dolphin Tiao hospitalized 30 & has a Kill Sheet...Made himself rare after that!

truebluebasher's picture
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truebluebasher commented Thursday, 13 Sep 2018 at 7:29pm

Sounds like I gave the Dolphins a bad I resolve that.

Saltwater story describes how Hunter Gowanda became a Dolphin pod leader.
Describes the last sea rise that formed the bond between Humans & sea creatures.

For 10,000's of years Humans have formed bonds with Dolphins.
From ancient Greece to Oz Saltwater Dolphin bonds.
Humans Signaled/Communicated even named,thanked & fed Dolphins.
* Sirensong to command & keep Life Guard Dolphins at Bay.
* Spear Tip/Sea Bed echolocation to Fishing Partners

Best I touch on the almighty power Echolocation
Speed of Sound= 343m /sec... (Speed of sound in Water = 1,500m/sec)
Meaning Dolphins can Echolocate 4x faster/better than Bats
Don't stop them droppin' in!

Story goes that a NSW elder was jealous of a Dolphin and as such killed the creature.
Apparently the bond & communication lines broke down for good.

Similar Stories abound the Pacific pertaining to Sharks as well.
Swim with school of Sharks is fine ...Kill one Shark...every day on you're Shark Bait!

Sure makes it easy to explain why Whales have returned... Family visited our break today!

simba's picture
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simba commented Thursday, 13 Sep 2018 at 8:06pm

Trueblue you might like this story.Back in the 70s we were down around Durras on the south coast and it was a flat day,so a good time to go for a snorkel.Well swam out along this drop off and laying in this dish /hole in the rocks on the bottom was a dolphin...just there with kelp washing over it with the wave movement ,exactly the right size like it was a custom made coffin and the kelp was the lid.....well it was a pretty spooky sight so on diving down i realized it was dead with a big lump on the side of its head but apart from that not a mark so how it ended up in that perfect spot ,whether it picked its place to die is a mystery.


The Fire's picture
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The Fire commented Friday, 14 Sep 2018 at 6:25am

Orcas are indeed dolphins true blue you got in first, credit +3. Dolphins DO deter sharks, just not the bottlenose type. Maybe deploy inflatable orcas instead of drumlinez??

Peace maaaan..

groovie's picture
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groovie commented Friday, 14 Sep 2018 at 6:29am

In 2016, an attack by a G/ White (5m+) on a mate @ Bulls paddock on the mid nth coast(near Boomerang Bch) where a large pod of dolphins displayed behaviours such as slapping the water with there tails & swishing their noses in the water before gathering in a tight pod under his board then fleeing the scene 30 sec before he was lifted 2m in the air by the huge predator in a classic ambush attack. This attack seems to back up your theory that the shark was following the dolphins looking for a victim, which my mate became after the dolphins hurriedly left leaving him as the perceived lone injured dolphin left behind as the pod flees.

truebluebasher's picture
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truebluebasher commented Friday, 14 Sep 2018 at 3:23pm

Swellnetonian's real life blood curdling shark tales raise more alarms.

Fanning "The Fire" @10-Shark Tank/ WSL order a dozen inflatable flaky Orca scare crows.

Killerwhale/Dolphin bro's both bow party waves to backwash meals off sloped shore.

Upfront comments are spot on! We know more of Scomo's caps than of our oceans.
Always read between the lines as continual updating will occasionally flip your research.

note:The Poolboy Porpoise & Kelp Bed are my untested theories, they scream in yer face?
Report in question focuses on warmer shallow bays but does touch on shallow acoustics.

W.A. inshore kelp of Summer Canopy & Winter understory far distants East coast dolphins.
W.A Dolphins use sponge nose cones but also may have blowholes impeded by canopy.
W.A Readers would be advised to apply massive seasonal kelp beds to Shark numbers.
I'm guessing the Kelp won't block the Alarm but corrupts the nature as to its source.
Echolocation travels 4x faster through rock than water or 8x faster than air! (As for Kelp?)

My theory unravels a perfect example of anomaly by lack of research.
a) Cetacean/Whale beachings of the frail or young tide naturally with Winter kelp blooms
b) Saltwater Fisherman echolocated from shore to hunting dolphins during kelp season.
Raises more questions than answers?
So is winter the worse time to echolocate or the best time to echolocate?
Do Humpback Whales echolocate? This answer has recently flipped from No!... to a Big Yes!
Don't infants have far better acoustics than Adults? Then why mostly infants wash ashore?

This flip flop continues daily about our Ocean and won't end with us nor in our lifetime.
Theories you are hearing for the first time in this column are all infant research.
WA ocean research is a vast & expensive resource requiring full public feedback as with here.

Above I touched on Dolphin's ultrasound ability to isolate dysfunctional body parts.
Waterpark Shark's {Pet Porpoise MD} [back after Golf]...isolates $2,000/hr from the infirmed!
Disclaimer: (online price only)."1hr pool therapy" includes Ultrasonic Smiley Flipper selfie.

The Fire's picture
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The Fire commented Friday, 14 Sep 2018 at 6:34pm


So gws are not the apex predator in our oceans. Orcas are. A gws got nailed in port lincoln a few years ago and guess what.. no more gws showed up for the cage dive operators for months. Zero sightings. Even though there has been no official attacks in the wild on humans by orcas, they scare me more than gws. I think its the team work and that tall dorsal fin. "Shivers"

Peace maaaan..

velocityjohnno's picture
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velocityjohnno commented Friday, 14 Sep 2018 at 6:49pm

TBB your posts are both cryptic and awesome.

truebluebasher's picture
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truebluebasher commented Friday, 14 Sep 2018 at 8:31pm

The Fire!...{ Orcas scared him more than Great Whites }... Bloody hardcore Aussie Epitaph!
(Far Out!) Remind me never to surf with you lot! "Say hello to Bruce!" He just wants a nibble!
Morning Dolphin surprise still gets a drawn out second stare! Bloody year older every time!

Your right though no "fatal" attacks I've come upon...not a lot of pro killer data.

Sept 9/1972 ...A Surfer was bitten by an Orca at Point Sur.
Californian Hans Kretschmer needed 100 stitches (all considered this as an attack)
Point Sur is a Killer Whale snack Bar serving up man sized cornflake crumbed Seals... is rare to source any other attacks in the wild apart from bumps/tugs/grabs.
Menacing Pod of 8 took over our local break back in '05 never seen them since... Epic!

truebluebasher's picture
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truebluebasher commented Friday, 14 Sep 2018 at 8:58pm

Your too kind and wiser than that velocityjohnno.
No substitute for captain's table old salt tales.
I'll most certainly join you in applauding our fellow Swellnet commentators of late.
Hands down the best read in town...thanx for the best forums Swellnet.

velocityjohnno's picture
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velocityjohnno commented Saturday, 15 Sep 2018 at 12:37pm

Cheers TBB, and agree these are great forums.

Before I add a link that will haunt you all for ever,

I've been lucky to see some great dolphin pod behaviour; 60 coming through Snapper to Rainbow while out among them; one surfing right under my wave at Pt Mac town beach, so fast; 50 or more forming a ring at an Esperance beach, while their young performed airs and flips inside the ring on an A frame peak. Babies similarly protected by adults popping airs in the shorebreak of some wedgey beachies north of Perth - they were tiny, a metre long perhaps? So cute! A pod that were drifting north to a northern headland on that mid NSW coast, we paddled out soon afterward to their south and 'coralled' them between the headland and us for a while. A lone bull dolphin, heading north on the WA midwest coast, battle scars over his whole upper body every time he surfaced as he passed me - I thought he had it tough.

But one experience, in light of what has been posted above, sends a shiver now. Out alone on an A frame reef down south WA, mate wanted to stay in car for a bit but I liked the look of the wave and went out. About 15mins in, a dolphin breaches out of the water within a boardlength of me, scared me witless. Decided to go in until others arrived.

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velocityjohnno commented Saturday, 15 Sep 2018 at 12:41pm