Wednesday 14th October 8.00pm
The documentary series examining freak occurrences in the natural world returns. The first instalment of the new run explores a remarkable clash between two oceanic predators. In 1997, stunned tourists on a whale-watching trip off the coast of California witnessed an orca seemingly attack, kill and eat a great white shark – a unique event that gave scientists a radical new perspective on the habits of both species.
Located 27 miles west of San Francisco in the North Pacific, the Farallones are a small group of barren islands that play host to one of the world’s greatest concentrations of great white sharks. Every autumn, the predators flock to the area to feed on the seals that gather on the rocks. Since 1987, scientists based on the islands have been studying the sharks and have built a detailed picture of their behaviour. On 4 October 1997, however, one extraordinary event altered the scientists’ entire perspective.
Marine biologist Peter Pyle was working on the islands when reports came in of a shark attack with a difference. A group of tourists on board whale-watching boat the Superfish had witnessed an orca – very rarely seen near the Farallones – apparently attack a great white. Pyle raced to the scene. “As we approached, you could see the killer whale with a shark in its mouth,” he recalls.
Pyle’s colleague Mary Jane Schramm was on board the Superfish and saw the event unfold. “We were extremely excited,” she says. “It was a very big shark.” Schramm and the tourists were watching two orcas frolic in the waves when the shark appeared. It approached the boat, then swam away – at which point one of the orcas sped towards it. Both animals then disappeared, only for the orca to emerge minutes later with the half-ton shark held upside down in its mouth. “It was like a cat with a mouse,” says Mick Menigoz, skipper of the Superfish. “This was a once-in-a-lifetime thing.”
In the immediate aftermath of the attack, Pyle used a pole camera to record the orcas underwater. The mammals had now torn the shark apart and proceeded to eat parts of it, including the liver. After 15 minutes, they left the area. “It was a complete surprise for us,” says Pyle. “We had no idea that could happen.” While it was clear that an orca had killed and eaten a great white, what was not clear was how the former had overpowered the shark without a struggle. Then within days, an even bigger question arose. After the attack, the entire great white population – up to 100 individuals – suddenly disappeared. What had triggered the departure and where did the sharks go?
With the help of footage of the incident recorded by the tourists, marine biologists surmised that the orca rammed the great white to stun it, then held it upside down to immobilise it. Scientists in the Bahamas have discovered that sharks can be induced into a trance-like state by turning them onto their backs – a condition known as ‘tonic immobility’. Apparently, certain groups of orca have made the same discovery. “Orca are very smart,” says expert Ingrid Visser. “I’m pretty sure that tonic immobility is part of the repertoire of the orca.” Having observed the whales off the coast of New Zealand for many years, Visser thinks it feasible that they could habitually target great whites as food.
As to why the sharks fled after the attack, New Jersey scientist Craig O’Connell believes it was because of the “smell of death” in the water. Tests with lemon sharks show that chemicals released when a shark is killed trigger a violent flight reaction in others of the same species. While this might explain the initial dispersal, however, it does not explain why the great whites would stay away from the Farallones for the rest of the feeding season – especially when later research proved that some of them travel up to 4,000km to be there every autumn.
The bizarre incident at the Farallon Islands still holds some mysteries, but it has shed light on the hierarchy amongst the ocean’s most fearsome killers. “In my mind it’s really clear –we have a top predator here,” says marine biologist Alisa Schulman-Janiger of the orca.