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I only skimmed it, but it doesn't seem that they looked directly at whether the sharks actually fear Orcas per se. It is already known that white sharks flee wh

I only skimmed it, but it doesn't seem that they looked directly at whether the sharks actually fear Orcas per se. It is already known that white sharks flee whenever one of their own is killed by anything, which they can smell from some distance away. They remember to avoid that area for some time afterwards. "Great White Sharks are terrified of Orcas" suggests a higher level of intelligence than "Great White Sharks evolved to fear anything that can kill a Great White Shark". It seems that the study is less concerned with that mechanism and more with the fact that this kind of displacement leads to White Sharks occupying sub-optimal hunting grounds while Orcas get to go wherever they want.

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cmyr 7y ago
The article says that even if orcas pass through an area where the sharks are hunting, the sharks will leave the area and not return for months. It does not mention any sharks being killed.
nrp 7y ago
Is that that different from human fears? We’ve presumably also evolved to be instinctually afraid of categories of things capable of harming or killing us, like snakes and spiders. Our intelligence lets us more carefully sub-categorize these into things that actually can kill us (Black Widows and Cobras) from things that can’t (Orb Weavers and Rat Snakes). Even then though, running across a big shiny Orb Weaver or Rat Snake in the wild shakes loose something deep in your brain telling you to stay away.
mr_toad 7y ago
I’m not sure it takes much intelligence to feel fear. Many fears can be highly instinctive and even irrational.
- mattkrause 7y ago
  The most common projection from the mouse retina is actually a highly-specialized and evolutionarily-conserved hawk detector. It responds to dark, looming stimuli against bright or grey backgrounds. This is one of my favorite discoveries: https://www.pnas.org/content/pnas/early/2012/08/08/1211547109.full.pdf https://www.pnas.org/content/pnas/early/2012/08/08/121154710...
  - RyanHamilton 7y ago
    Thanks for that link, that was an interesting read.
mattkrause 7y ago
I am all for pairing naturalistic observations with more controlled experiments. However, actively harassing adult great white sharks would be one hell of a thesis project.
s1k3b8 7y ago
> It is already known that white sharks flee whenever one of their own is killed by anything But white sharks fight each other, kill each other and even eat each other on occasion. We know that white sharks fetuses cannibalize each other in the womb. How could they do that if white shark blood scares them off? Also, is there really a difference in smell between white sharks and other sharks, seals, etc? This is such an easy thing to test. Has anyone taken white shark blood and tested it on white sharks ( captive or wild )? Also, does this only work on white sharks? Do tiger sharks, nurse sharks and other sharks fear blood of their own species? Finally, white sharks are scavengers as well as hunters ( like most predators ). As far as I know, every scavenger will cannibalize when given the chance. Are white sharks the exception? Also, most animals flee when they see, smell or hear a predator. So I think it's most likely that white sharks flee when they sense a potential predator. If truly shark blood scares off sharks, then coast guards should dump some shark blood near beaches where sharks frequent.
- olivermarks 7y ago
  Hollywood/Spielberg promoted the fantasy that sharks are predatory to humans, where we are more often mistaken for seals and other natural shark prey when out in the water. An acquaintance recently told me he was surfing at Salmon Creek a couple of weeks ago and a great white hit him on the back of his head with a powerful flick of his tail while he was laying prone on his longboard, a wave came along almost immediately after this and took him shore wards (still prone). This was almost certainly a 'seal slap' stun move, sharks don't do anything by accident. My friend then saw another surfer on his way in paddling out who saw the shark silhouette in the wave and headed back to the beach. It's scary but there are very few actual shark bites and kills of humans despite the terror film sell, but it is still a mystery how we can discourage them from the coastal beach waves where they have every right to be. Despite dolphin's adorable perception by humans you can see them torturing and raping seals in the San Francisco bay, it's a jungle out there...
  - dfc 7y ago
    Dolphins are raping seals off the coast of San Francisco?

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cmyr 7y ago

The article says that even if orcas pass through an area where the sharks are hunting, the sharks will leave the area and not return for months. It does not mention any sharks being killed.

nrp 7y ago

Is that that different from human fears? We’ve presumably also evolved to be instinctually afraid of categories of things capable of harming or killing us, like snakes and spiders. Our intelligence lets us more carefully sub-categorize these into things that actually can kill us (Black Widows and Cobras) from things that can’t (Orb Weavers and Rat Snakes). Even then though, running across a big shiny Orb Weaver or Rat Snake in the wild shakes loose something deep in your brain telling you to stay away.

mr_toad 7y ago

I’m not sure it takes much intelligence to feel fear. Many fears can be highly instinctive and even irrational.

mattkrause 7y ago
The most common projection from the mouse retina is actually a highly-specialized and evolutionarily-conserved hawk detector. It responds to dark, looming stimuli against bright or grey backgrounds. This is one of my favorite discoveries: https://www.pnas.org/content/pnas/early/2012/08/08/1211547109.full.pdf https://www.pnas.org/content/pnas/early/2012/08/08/121154710...
- RyanHamilton 7y ago
  Thanks for that link, that was an interesting read.

mattkrause 7y ago

I am all for pairing naturalistic observations with more controlled experiments. However, actively harassing adult great white sharks would be one hell of a thesis project.

s1k3b8 7y ago

> It is already known that white sharks flee whenever one of their own is killed by anything But white sharks fight each other, kill each other and even eat each other on occasion. We know that white sharks fetuses cannibalize each other in the womb. How could they do that if white shark blood scares them off? Also, is there really a difference in smell between white sharks and other sharks, seals, etc? This is such an easy thing to test. Has anyone taken white shark blood and tested it on white sharks ( captive or wild )? Also, does this only work on white sharks? Do tiger sharks, nurse sharks and other sharks fear blood of their own species? Finally, white sharks are scavengers as well as hunters ( like most predators ). As far as I know, every scavenger will cannibalize when given the chance. Are white sharks the exception? Also, most animals flee when they see, smell or hear a predator. So I think it's most likely that white sharks flee when they sense a potential predator. If truly shark blood scares off sharks, then coast guards should dump some shark blood near beaches where sharks frequent.

olivermarks 7y ago
Hollywood/Spielberg promoted the fantasy that sharks are predatory to humans, where we are more often mistaken for seals and other natural shark prey when out in the water. An acquaintance recently told me he was surfing at Salmon Creek a couple of weeks ago and a great white hit him on the back of his head with a powerful flick of his tail while he was laying prone on his longboard, a wave came along almost immediately after this and took him shore wards (still prone). This was almost certainly a 'seal slap' stun move, sharks don't do anything by accident. My friend then saw another surfer on his way in paddling out who saw the shark silhouette in the wave and headed back to the beach. It's scary but there are very few actual shark bites and kills of humans despite the terror film sell, but it is still a mystery how we can discourage them from the coastal beach waves where they have every right to be. Despite dolphin's adorable perception by humans you can see them torturing and raping seals in the San Francisco bay, it's a jungle out there...
- dfc 7y ago
  Dolphins are raping seals off the coast of San Francisco?