Story behind the video (which I gleaned from a documentary on National Geographic Channel): A whale-watching boat encountered a couple of orcas in the waters near San Franciso. Then one lady on the tour spots (and films) a large great white shark cruising alongside the whale-watching boat. Well apparently one of the orcas spotted the shark too, and went after it. Long story short, the orca kills the shark for its liver (which is apparently a specialty food for this particular orca).
(As an aside, I had previously assumed great white sharks were the baddest animals in the ocean. I stand corrected.)
Anyway, it turns out that dozens of the great whites in this area had been fitted with radio tags and were being tracked by researchers, and the NGC show mentioned that when this attack occurred, the other great whites in the area immediately scattered in all directions. Which raised the question in my mind: How did they know? How did these sharks know that an attack on another great white had occurred? Or that it might be dangerous to be a great white in this vicinity? Did the shark which was killed somehow communicate this? Is there some form of shark-to-shark communication going on, of which we are not aware? Did the dying shark “scream” in some “language” to which we are not privy?
And yes, of course, there was white shark blood in the water, but could it really be dispersed and sensed by the other sharks in the area as immediately as the NGC narrative implied? Could it have been just that smell that sent the other sharks scurrying away?
I havent seen the show but more information about the size of the area where ‘sharks were running away from’ would be needed. And how credible this claim really is.
If its in visual range as would be my bet, then it will simply be that Orcas are a large creature that they view as a threat and quite sensibly avoid, they have pretty good eyesight and can see a fair way.
Ive seen this in a sardine run on video when a whale comes in to feedon the sardines, and the sharks shoot away from it in all directions at light speed, even though it was a baleen type whale rather than one likely to actually eat sharks.
I think all answers will border on WAG, but here’s mine:
Sharks may not be deep thinkers, but I suspect they know when they are potential lunch. A good-sized great white is about 5 meters and 2+ tons. An average male killer whale is 6-8 meters and 6 tons. Sure, a shark can bite back and do damage, but they’re obviously outclassed, not even taking brain capacity into account.
And how close does, “in the vicinity” mean? If the sharks were in the same water as the killer whales, and were aware of their presence, I wouldn’t find it too surprising that a shark would swim away when its fish-in-distress sensors shot off the scale.
Sharks are awesome, and the great white is a time-tested evolutionary design, but there is a very good reason killer whales have that name.
IIRC it was something like 100 sharks, so they couldn’t have all been in the immediate vicinity. Unfortunately, the NGC broadcast didn’t dwell on the fleeing sharks, it just sort of mentioned them in passing, so I don’t have as much detail as I’d like.
Don’t sharks have a sophisticated sensory array along their “lateral line” which can pick up distress signals at a range of, oh, very far - miles even? Wouldn’t it be possible that they can tell the difference between “disruption = distress = lunch; come fast” and “disruption = something bad for you; swim away”?
Inner ear - sound - 900 m range
Lateral line - vibration - 200 m
Olfactory sacs - smell - 180 m
Ampullae of Lorenzini - temperature, weak electrical fields (20-30 cm), salinity, water pressure
Eye - sight - twice as effective as cat’s eye for dim vision; 30+ m
This says “Most sharks can detect blood and animal odors from many miles away.”
Cool. So that means that if they smell, say, the blood of a great white in the water (meaning they can differentiate between the blood of different animals) they should swim away?
I did see the Nat Geo show, and the supposition is that dying/dead Great Whites release a chemical signature that alerted the others to flee. Presumably it’s not used too often.
A shark-repellent manufacturer was showing great interest in trying to identify and synthesize this chemical. One of the trials (on small sharks in shallow water) did indeed instantly panic a shark which had been put into a trancelike state by being held upside-down.
So again, we don’t know how “immediately” they high-tailed it, or how close “in the area” was. It would seem that a chemical trail released in the water would travel somewhat slowly. But maybe it’s faster that it would seem.
It looks like the scientists called on the scene wrote it up:
Pyle, P., M.J. Schramm, C. Keiper, and S.D. Anderson. 1999. Predation on a
white shark by a killer whale and a possible case of competitive exclusion.
Marine Mammal Sci. 15:563-568.
I don’t have access to the article but maybe some one out there does.
I have a copy of the paper - anything in particular you want to know? I won’t post the whole thing due to the copyright rules, but here’s a description of the attack:
In addition, unique events such as predation on a white shark by killer whales at SEFI [Southeast Farallon Island] in 1997 and 2000, and the subsequent disappearance of white sharks from the island (Pyle et al. 1999) after both predation events, may affect both the short-term and long-term population dynamics of white sharks off California.
In other words, sure looks like the sharks left because of the killer whales, but how they knew or how the killer whales arranged it is unknown at the moment.
There is this paragraph in the paper which may be relevant:
So it is not clear how fast the sharks evacuated the area (hours, maybe days), but they didn’t come back for at least 2 months. Also they say in the paper that the killer whales remained in the area for the duration of the observations, which probably kept the sharks away on top of the initial scare.
My total WAG is that the orcas were vocalizing a “look! shark! get him!” (or maybe just some basic hunting cue) signal to the other orcas, and the other sharks in the area picked up on that and high-tailed it.
Yeah - in addition to the above, they mention that white shark attacks on pinnipeds were average through October 3rd, 1997, and after the October 4th attack by a killer whale on a white shark, only 2 more white shark attacks on pinnipeds were recorded during the rest of the fall - on Oct. 15 and Nov. 23. Only two attacks during that time period is significantly different from the 1989-1996 average number of white shark attacks on pinnipeds.
Sadly, sounds like an impossible proposal - how can you be sure you’ll observe another orca/white shark attack? In general, very rare events make a poor basis for research funding.
There are currently better tagging/tracking studies of sharks than there were 10 years ago, though, look at: Pelagic Shark Research Foundation The Pelagic Shark Research Foundation - Research - Methods and PRBO Conservation Science (http://www.prbo.org/cms/157) continues research. Who knows, maybe the next time it happens, we’ll get better information off it.
I’m wondering if the shark(s) that made those last two seal attacks was a late comer and was wondering where everybody was: Hellooooo? C’mon guys, where is everybody?
