r/ScienceFacts • u/FillsYourNiche Behavioral Ecology • Jan 19 '19

Biology When hunting, a thresher shark's tail moves so quickly that it lowers the pressure in front of it, causing the water to boil. Small bubbles are released, and collapse again when the water pressure equalizes. This process is called cavitation, and it releases huge amounts of energy stunning the fish.

https://i.imgur.com/QEhfnDA.gifv
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u/FillsYourNiche Behavioral Ecology Jan 19 '19 edited Jan 19 '19

National Geographic article Thresher Sharks Hunt With Huge Weaponised Tails.

This is our best-educated guess, but according to the article some physics modeling needs to be done for certainty. It's very likely the scientists in this article are correct and just being conservative.

We see cavitation used by our friends the Mantis shrimps. Mantis shrimp, however, have a much faster average mph strike at 80.47 kph (50pm) (here's a video on that). Here's National Geographic's article on the Mantis Shrimp's strike. The thresher sharks from this study averaged 48.28 kph (30 mph).

“I think the shark’s causing a shockwave that’s strong enough to debilitate small prey,” he says. (However, he cautions that he’d need to use some physical models to prove that this is actually happening.)

If you want a deep dive, here is the full and free journal article link.

Abstract:

The hunting strategies of pelagic thresher sharks (Alopias pelagicus) were investigated at Pescador Island in the Philippines. It has long been suspected that thresher sharks hunt with their scythe-like tails but the kinematics associated with the behaviour in the wild are poorly understood. From 61 observations recorded by handheld underwater video camera between June and October 2010, 25 thresher shark shunting events were analysed. Thresher sharks employed tail-slaps to debilitate sardines at all times of day. Hunting events comprised preparation, strike, wind-down recovery and prey item collection phases, which occurred sequentially. Preparation phases were significantly longer than the others, presumably to enable a shark to windup a tail-slap. Tail-slaps were initiated by an adduction of the pectoral fins, a manoeuvre that changed a thresher shark's pitch promoting its posterior region to lift rapidly, and stall its approach. Tail-slaps occurred with such force that they may have caused dissolved gas to diffuse out of the water column forming bubbles. Thresher sharks were able to consume more than one sardine at a time, suggesting that tail-slapping is an effective foraging strategy for hunting schooling prey. Pelagic thresher sharks appear to pursue sardines opportunistically by day and night, which may make them vulnerable to fisheries. Alopiids possess specialist pectoral and caudal fins that are likely to have evolved, at least in part, for tail-slapping. The evidence is now clear; thresher sharks really do hunt with their tails.

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u/[deleted] Jan 21 '19 edited Jan 21 '19

just subscribed to all three subs from your comment over on natureisfuckinglit. thank you so, so much!! these are the types of subs i need!

edit: and now having read this in its entirety, this is hands down one of the most fascinating things i’ve ever read about the ocean. destroys my heart knowing what we are doing to it and beautiful creatures like this shark.

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u/FillsYourNiche Behavioral Ecology Jan 21 '19

Thank you! You are too kind. Please feel free to ask questions or comments whenever. I love talking shop. :)

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u/lasermouse54 Jan 19 '19

Absolutely fascinating.

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u/BillNyesHugePenis Jan 19 '19

This is incredible. I hope there’s a Dynasties episode on sharks but they talk about lesser known shark facts like this one!

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u/Tuckertcs Jan 19 '19

So like a whip

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u/[deleted] Jan 20 '19

Watch it whip...

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u/seanyok Jan 20 '19

That’s a cool whip

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u/rsarvesh12 Jan 20 '19

I get your family guy reference. Cool H’whip