Meanwhile in the Galapagos, orcas are bringing the hammer down.

Wildlife videographer Roberto Ochoa has been leading expeditions around Darwin's favourite archipelago for years, but even for such a seasoned diver, this particular encounter stood out. 

Ochoa watched on as a group of orcas* killed and ate what appears to be a scalloped hammerhead shark (Sphyrna lewini). We're certainly familiar with shark-eating orcas, but this kind of footage is extremely rare. In fact, just a handful of orca-on-hammerhead predations exist on record.

"[It's] inspiring footage," Ochoa wrote on Instagram, adding that the clip was filmed near Gordon Rocks, a known biodiversity hotspot located about an hour offshore from the islands.

Scientists used to think events like this one were¬†extremely rare, occurring¬†only when other prey¬†was scarce. But evidence is mounting to suggest that ‚Äď at least in some locations ‚Äď certain orca pods actually¬†specialise in hunting¬†sharks and rays (elasmobranchs).¬†

According to Orca Research Trust biologist Dr Ingrid Visser, New Zealand orcas are known to feed on as many as ten different elasmobranch species, and they've even developed distinct strategies for tackling them. When it comes to bottom-dwelling rays, for example, a tandem hunting tactic is adopted: one whale restrains the ray (and its pesky stinger!), while its partner delivers the fatal bite. Small sharks, on the other hand, are pushed to the surface and stunned.

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Illustration showing the orcas' strategy for hunting thresher sharks. Image: Visser/Orca Research Trust

Visser witnessed this clever¬†strategy back in 2002, when two local whales ‚Äď known to researchers as¬†"NZ60" and "NZ19" ‚Ästtook down a thresher shark. Like a pair of water benders, the orcas used their tails to create a powerful vortex, which forced¬†the shark top-side.¬†

"Once at the surface, NZ60 pivoted and lifted her tail clear out of the water and brought it down sideways onto the shark, striking it about mid-body," writes Visser in a description of the event. "NZ19 then repeated that sequence." This went on until the animal was so dazed it couldn't swim away. 

A smooth hammerhead was taken down shortly after, and the same strategy has been used on other sharks.

So, was Ochoa's encounter in the Galapagos an example of similar hunting behaviour? At this point, we can't be sure. (As of this posting, he has not responded to our request for more information about the sighting.) 

You might be wondering why predators of this calibre would even bother with such hunting strategies. After all, the monochrome behemoths¬†are certainly capable of out-swimming most sharks.¬†So why not just charge at full speed and pummel one? It's possible that¬†other attributes besides speed and brute force ‚Ästlike agility ‚Ästcome into play here. Hammerheads in particular are¬†extremely flexible,¬†so they¬†can outmanoeuvre their attackers with a little luck on their side. Using the tail flukes while hunting might also¬†provide some kind of tactical advantage for the orcas. By keeping¬†its toothy end¬†away from¬†a shark, an orca could be protecting its own¬†vulnerable organs (like the eyes) from the opposing toothy end.

Of course, there's also a third, slightly unnerving, option: the whales could simply be playing with their food. We saw an example of that in the notorious seal fling filmed off Victoria, Canada back in 2015 (viewer discretion advised). When it comes to punting sharks, however, orcas don't seem to waste any time between the initial whack and the trip down the gullet, suggesting nothing playful is going on.

The New Zealand pods are¬†certainly emerging as a distinctive population of shark-eaters, but big fish¬†are on the menu for orcas elsewhere in the world, too ‚Äď and we're learning more about that each year.

Back in December, an orca in California was seen with a blue shark snack (keep an eye on the left flipper of the whale on the right):

Tiger sharks, sevengill sharks¬†and even great whites¬†are also known potential targets, but because most of these predations¬†occur in deep water, and¬†visibility tends to be poor, it's hard to say just how¬†frequently such events occur in the region ‚Äď though we do have clues. ¬†

Some offshore orcas along the eastern Pacific, for example, have been found with teeth worn down to the gums,¬†a nasty side effect of eating food that has sandpaper skin. This dental dilemma hasn't been documented in the Galapagos, however ‚Ästin fact, orca sightings in general are relatively uncommon in that part of the world. This makes Ochoa's sighting all the more incredible.¬†

* There has been some debate about the vocalisations that can be heard in Ochoa's clip. We may be hearing both the orcas and some humpback whales nearby. 

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Top header image: Hélène Surmont/Flickr