Wednesday, 4 December 2013

The KILLER whale

The Myriad of Killer Whale Hunting Techniques

by Rob Cooper

A titanic black shape emerges from the sea, huge leering white eyes aflame with malice rip through the sheet of water accompanying the streamlined monster as it emerges from the surf. Noticing its end far too late a seal barely has time to turn before it is grabbed by the neck and twisted voraciously around as the black and white menace of the deep, rather clumsily, makes its way back to the ocean.

Of course we are all well aware the killer whale or Orca is no monster but a simple animal, just as humans are. We’re also aware the large white areas on the flanks of the whale are not its eyes. However the immense range of prey and hunting practices employed by the mighty orca seems to have no compare outside of humans. Indeed the killer whale is one of the only animals in the world to be seen engaging in recreational hunting that can last for days in length (spending over 12 hours chasing and drowning a whale calf only leave all but the tongue and lower jaw uneaten) and has been recorded in several studies to have hunting success rates of nearly 100% on several prey types. This, it hardly needs clarification, is pretty much unmatched anywhere outside our own species.

How does the killer whale do this? What gives it an edge over predators such as sharks which are so well adapted they have remained almost completely unaltered over millions of years? And how do they manage to prey on so many different prey types with little morphological variation?

The answer is relatively simple: Intelligence

Killer whales have an enormous number of hunting strategies that are all applicable to different prey items which allow the different types to predate on a huge variety of marine fauna and avoid injury to themselves even with predating on creatures ten times their size.

Fish herding
Many groups of killer whales herd fish either into shallow water or to the surface by using the pod of whales to encircle and trap the fish. Norwegian killer whales take this a step further and use their tail flukes to stun vast swathes of fish which they can then pick of at their leisure. The combination of concentrated fish and the huge area of effect and stunning impact of the tail flukes means the whales can harvest huge amounts of fish with no need to spend energy chasing and catching individual fish. Some fish are completely pulverised by the huge tail fluke and end life merely as a bloody smear in the wake of their gargantuan predators.

Ice Floats
The only place your safe from killer whales is land right? Unfortunately this turns out to be wrong. Antarctic orcas have learnt to move in unison to create huge waves in the water that can wash seals and/or walrus from ice floats that they take refuge on. The whales actually break apart the ice floats using the movement of their own bodies to generate waves and proceed producing currents to move the floats to open water. This cuts off all avenues of escape and they then displace the seal from the ice with animal generated waves. By this point the seal is so exhausted from being repeatedly knocked of the ice float it has almost no energy to resist the whales attack and with deep water to emerge from the whales are comparatively safe from the seals jaws.

Killer whales targeting ice floats

The classic Orca hunt as mentioned in the first paragraph involves the emergence of the great animals onto land to catch a presumably very surprised and terrified seal: which is a decidedly risky strategy for such a large marine mammal that would crush its own organs under its body mass if it became trapped on the beach. The tactic however seems to work as adult killer whales can be seen nudging younger whales onto the beach in order to learn the trick for themselves. There remain few sights as awe inspiring and terror inducing as a six tonne wall of muscle emerging from the sea to capture its prey.

Orca beaching 

Shark Eaters
Many Killer whale groups have mastered the art of tackling sharks and stingrays through a lesser known phenomena entitled tonic immobility. The whales use their tail flukes or generate currents in order to flip the shark or ray onto its back. Once this has been achieved the shark or ray is completely paralysed whilst it remains on its back and the lethal sting of stingrays becomes inert. Killer whales finding great white sharks in their feeding grounds have been known to ram the shark at full speed and proceed to pull the creature to the surface and eat it alive. In this case the shark documented was a three meter long great white shark attacked by two killer whales who were feeding on the shark’s normal prey of sea lions near San Francisco.

Whale Hunting
Killer whales are second only to humans in their ruthless hunting of giant baleen whales. Antarctic killer whales have been described performing complex cooperative attacks on Bowhead whales with some whales immobilising the prey by attacking the flippers whilst others rammed the whale to cause internal damage such as broken ribs and finally the other whales swam on top of the Bowhead to cover the blowhole and force the Bowhead underwater to drown it. Antarctic killer whales are known to pursue the Finn whale to exhaustion in marathon 12 hour hunts with each whale taking its turn at the head of the pursuit. Killer whales have even been known to attack the giant sperm and blue whales with aggressive bull sperm whales and fully grown blue whales being pretty much the only animals safe from killer whale predation.