Friday 8 June 2012

Great white shark versus orca

 In some parts of the world, orcas and great whites frequent the same waters, but do they get on?



Which is the greatest ocean predator – the orca or the great white shark? A shocking encounter off the Californian coast reveals the answer.


When wildlife-watchers in a boat off the Farallon Islands witnessed an orca attacking a great white shark, they were astonished by how easily the fish was overpowered. However, much of the action took place out of sight, under water. Scientists have pieced together the evidence to construct the likely sequence of events that led to the shark’s apparently timid demise.
From the eyewitness accounts, it was clear that the orca didn’t bump into the great white by chance. It deliberately changed course to intercept its victim. The shark appeared unaware that it was in danger.
Swimming at top speed, the orca took the shark by surprise, ramming it hard on the flank. The massive impact stunned the shark, leaving it momentarily confused and vulnerable.
With the shark dazed, the orca grasped it behind the head and turned it upside- down. The shark panicked and its brain released calming serotonin that sent it into a trance. This made it far easier for the orca to drown its prey.
Soon the shark was dead and the orca could start tearing it apart.




CLASH OF THE TITANS:
ORCA Orcinus orca
SIZE: Adult male up to 9.5m; adult female up to 8.2m.
WEIGHT: Male up to 5,600kg; female up to 3,600kg.
TEETH: 40–52 large, conical, inward-curving teeth in upper and lower jaw.
MAX SPEED: Bursts of 50kmph when in pursuit of prey.
TYPICAL PREY: Mostly fish and squid; also seals, sealions and other marine mammals and seabirds. Consumes up to 200kg of food daily.
MAX PREY SIZE: Several records of orcas attacking and eating grey whale calves.
HUNTING TECHNIQUE: Often works in teams to corral fish or to distract prey to isolate or weaken it before delivering the killer blow.
SPECIAL SKILLS: Uses echolocation – a form of sonar – to detect shoals of fish under water.
DISTRIBUTION: Found in all of the world’s oceans, but most abundant in cooler waters at high latitudes.


GREAT WHITE SHARK Carcharodon carcharias
SIZE: 4–5.5m fully grown; occasionally over 6m. Females generally larger.
WEIGHT: Usually up to 1,000kg; rarely up to 2,200kg.
TEETH: 3,000 razor-sharp, triangular teeth arranged in several rows that rotate towards the front of the mouth, replacing broken ones as needed.
MAX SPEED: Often reaches 40kmph.
TYPICAL PREY: Mostly big fish, including tuna, rays and other sharks; also seals, sealions, dolphins, turtles and seabirds.
max prey size Sometimes attacks and kills smaller great whites
HUNTING TACTICS: Solitary, ambushes prey from below with a powerful surge.
SPECIAL SKILLS: Excellent sense of smell: can detect a drop of blood in 100 litres of water. Electromagnetic sense picks up the magnetic field produced by muscle activity in its prey.
DISTRIBUTION: Found almost worldwide, from the subtropics to cooler, temperate seas; some populations highly migratory.

DID YOU KNOW? Great white sharks will sometimes eat whales but usually only after they're dead. There are numerous records of sharks scavenging whale carcasses. 



Source: discoverwildlife

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